NOAA Technical Memorandum NOS OR&R 9 

 

Guidance on Sensory Testing and Monitoring of Seafood for

Presence of Petroleum Taint Following an Oil Spill 

Seattle, Washington 

August 2001 

NOAA NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION 

National Ocean Service 

NOAA Technical Memorandum NOS OR&R 9 

Guidance on Sensory Testing and Monitoring of Seafood for

Presence of Petroleum Taint Following an Oil Spill 

Terriann I. Reilly

National Oceanic and Atmospheric Administration/National Marine Fisheries 

Service 

Seafood Inspection Program 

Roberta K. York 

Canadian Food Inspection Agency 

Laboratories Directorate

Seattle, Washington 

Donald L. Evans, Secretary 

U.S. Department of Commerce 

Scott B. Gudes 

Acting Under Secretary for 

Oceans and Atmosphere 

and NOAA Administrator/ 

Deputy Under Secretary for 

Oceans and Atmosphere 

Margaret A. Davidson 

Acting Assistant 

Administrator 

for Ocean Services and 

Coastal Zone Management

NOAA National Ocean 

Service 
Office of Response and Restoration 

National Ocean Service 

National Oceanic and Atmospheric Administration 

U.S. Department of Commerce 

Silver Spring, Maryland 

NOTICE 

This report has been reviewed by the National Ocean Service of the National Oceanic 

and Atmospheric Administration (NOAA) and approved for publication. Such approval 

does not signify that the contents of this report necessarily represent the official position 

of NOAA or of the Government of the United States, nor does mention of trade names or 

commercial products constitute endorsement or recommendation for their use. 
Foreword 

After an oil spill occurs, government regulatory authorities and other concerned 

parties may choose to conduct sensory testing of seafood that may have been exposed. 

If sensory testing is conducted, it must be carried out in a scientific and legally defensible 

manner. To date, there are few standard procedures published for this type of sensory 

testing (Bett et al. 1997). This document was written to provide guidance for conducting 

sensory testing on seafood suspected of petroleum taint. 

Development of these guidelines was supported and partially funded by 

NOAA/NOS Office of Response and Restoration. The document was written by sensory 

scientists from the National Oceanic and Atmospheric Administration /National Marine 

Fisheries Service (NOAA/NMFS) Seafood Inspection Program and from the Canadian 

Food Inspection Agency (CFIA). In addition to the two principal authors, many other 

individuals have made significant contributions to this document by communicating 

practical suggestions gained from their actual work experiences as seafood inspectors 

and laboratory professionals. The extensive bibliography (Section 9.0) provides 

supplemental resources for more in-depth information on sensory testing in general and 

for sensory testing specifically for taint. 

These guidelines are the result of collaborative efforts to address the need for 

standard sensory testing procedures for petroleum taint. By issuing these guidelines, 

NOAA does not intend to imply that sensory testing should be conducted after every oil 

spill that potentially involves seafood, or that a closure should be the end-point if taint is 

detected. The need for sensory testing should be assessed on a case-by-case basis 

after each oil spill because each spill is unique. 

Acknowledgments 

Special thanks for the editorial contributions of Ruth Yender and Nancy Peacock, 

National Ocean Service, NOAA, and for the invaluable information and practical advice 

from the seafood inspectors of the USDC/NOAA Seafood Inspection Program, and the 

U.S. Food and Drug Administration.

We acknowledge also the contribution of the technical review committee 

consisting of: Larry Hufnagle and Dr. Margaret Krahn from the NOAA/NMFS NW 

Fisheries Science Center, Dr. Alvin Rainosek of the University of Alabama, Mr. James 

Barnett and Dr. Aladar Bencsath of the U.S. Food and Drug Administration, Dr. Lyle 

Lockhart from the Canadian Department of Fisheries and Oceans, and Ruth Yender, 

with the NOAA National Ocean Service.

 Contents

1.0 Scope and Use of Guideline..............................................................................1

 1.1 Introduction...............................................................................................1

 1.2 Scope and use .........................................................................................2

 1.3 A few words about terminology.................................................................3

2.0 Collection and Preservation of Seafood Samples for Sensory Evaluation .5

2.1 Introduction...............................................................................................5

2.2 Types of samples to be collected .............................................................5

2.3 Timing of sampling during the oil spill and cleanup ..................................6

2.4 Handling samples during and after collection ..........................................7

2.5 Ready-to-use sampling kit ........................................................................9

2.6 Chain of custody and ensuring validity and integrity of sensory

samples................................................................................................9

2.6.1 Collecting seafood samples.....................................................9

2.6.2 Ensuring chain of custody (continuity of evidence)................10 

2.6.3 Secure shipping of frozen samples ........................................11 

2.7 Statistical sampling requirements...........................................................12

2.7.1 Basic types of statistical sampling plans..................................12

2.7.2 Required sample sizes and presentation for sensory 

testing ...................................................................................13

2.8 Species-specific collection procedures...................................................14

2.8.1 Finfish ......................................................................................14

2.8.2 Crustaceans and molluscan shellfish.......................................15

3.0 Selecting Appropriate Sensory Test Methods and Assessors ...................17

3.1 Introduction.............................................................................................17 

3.2 Subjective vs. objective sensory testing ................................................17 

3.2.1 Subjective testing ..................................................................17 

3.2.2 Objective testing ....................................................................18 

3.3 Selecting a sensory approach – general considerations ........................18 

3.3.1 What answers are required? .................................................18 

3.3.2 Assessor type.........................................................................18 
3.3.3 Numbers of assessors needed ..............................................19 

3.3.4 Assessor availability...............................................................19 

3.4 Test selection .........................................................................................20

3.4.1 Discriminative testing .............................................................20 

3.4.1.1 Difference testing using the triangle test ....................20 

3.4.1.2 Difference-from-control (DFC) testing ........................21 

3.4.2 Descriptive Analysis testing ...................................................22 

3.4.3 Testing with product experts and official inspections .............22 

3.5 Selecting an assessor type.....................................................................23

3.5.1 Two types of assessor panels appropriate for seafood taint 

assessment............................................................................23 

3.5.2 Recommended assessor types..............................................25 

3.5.2.1 Expert assessors........................................................25 

3.5.2.2 Trained and monitored assessors ..............................26 

3.6 Criteria for selecting expert and/or trained assessors...........................26

3.6.1 Time required to assemble a panel of assessors...................26 

4.0 Selecting, training, and validating sensory assessors.................................28 

4.1 Expert assessors ...............................................................................28

4.1.1 On-site validation ....................................................................28

4.1.1.1 Sequential testing......................................................28

4.1.1.2 Triangle test ..............................................................29

4.1.2 Training expert assessors........................................................30

4.1.3 Monitoring expert assessors....................................................31

4.2 Trained assessors..............................................................................31

4.2.1 Selecting assessor trainees.....................................................31

4.2.2 Training assessors ..................................................................32

4.2.3 Monitoring trained assessors...................................................32

4.3 Experimental design and data analysis for testing assessors 

(both expert and trained assessors) ..................................................32 

4.4 Test systems for assessor selection (both expert and trained

assessors)..........................................................................................34

4.4.1 Model system solution of water-soluble fraction of 

petroleum ...............................................................................34
4.4.2 Tainted and non-tainted known samples .................................35

4.4.3 Solutions of 1-butanol ..............................................................35

4.5 Data analysis for evaluating assessor candidates..................................36

4.5.1 Data analysis for difference-from-control test ..........................36

4.5.2 Data analysis using SAS..........................................................36 

4.5.3 Data analysis using Microsoft ExcelTM ....................................38 

5.0 Facility Requirements for Sensory Evaluation of Seafood .........................39

 5.1 Maintaining a neutral environment..........................................................39

 5.2 Sensory testing at the spill site ...............................................................40

5.3 Sensory testing in the laboratory ............................................................40

5.3.1 Sample-preparation area in the laboratory ..............................41

5.3.2 Sensory-evaluation (testing) area in the laboratory .................42

5.3.3 Workshop facility......................................................................43

5.3.4 Booth facility.............................................................................44

6.0 Sample Handling, Preparation, and Presentation in the Laboratory...........45

6.1 Personnel involved in sample handling, preparation, and presentation .45

6.2 Secure handling of samples ..................................................................45

 6.2.1 Sample receiving....................................................................45

6.2.2 General principles of sample preparation ..............................46

6.2.2.1 Intact organism samples ...........................................48

6.2.2.2 Pooled, blended samples..........................................48

 6.2.3 Storing samples .....................................................................49

 6.3 Sample preparation for sensory testing..................................................49

6.3.1 Intact single/multiple organism samples ..................................50

6.3.2 Blended, pooled samples.........................................................51

6.4 Sample presentation in the evaluation area ...........................................51

6.4.1 Preliminary preparations ........................................................51 

6.4.2 Sample placement and timing................................................51 

6.4.3 Presentation of intact organism samples ...............................52 

6.4.4 Presentation of pooled, blended samples ..............................52 

 6.5 Assigning random-sample presentation sequences...............................53
7.0 Sensory Evaluation Protocols ........................................................................55

7.1 General sensory testing procedures.......................................................55 

7.2 General instructions for expert assessors .............................................56 

7.2.1 Before testing...........................................................................56 

7.2.2 During testing...........................................................................57 

7.2.3 Evaluation criteria ....................................................................58 

7.2.4 Evaluation ballots ....................................................................58 

7.3 General instructions for trained assessors .............................................59

 7.3.1 Before testing...........................................................................60 

 7.3.2 During testing...........................................................................60 

7.3.3 Evaluation criteria ....................................................................61 

7.3.4 Evaluation ballots.....................................................................61

8.0 Collection and Analysis of Test Data and Decision Criteria ........................63

8.1 Introduction.............................................................................................63 

8.1.1 Expert assessors....................................................................64 

 8.1.2 Trained assessors....................................................................64 

8.2 Test data types and numbers of assessors needed...............................65 

8.2.1 Data types................................................................................65 

8.2.2 Number of expert assessors needed.......................................65 

8.2.3 Number of trained assessors needed......................................65 

8.3 Design and content of evaluation ballots................................................66 

8.3.1 Ballots for expert assessors.....................................................66 

8.3.2 Ballots for trained assessors....................................................67 

8.4 Test data analysis ..................................................................................67 

8.4.1 Expert assessors .....................................................................67 

8.4.2 Trained assessors....................................................................68

 8.5 Decision criteria ......................................................................................69

8.5.1 Expert assessors .....................................................................69

8.5.2 Trained assessors....................................................................69

9.0 Bibliography .....................................................................................................71
Appendices 

Appendix 1 Normative References - Existing guidelines, standard practices, and 

sampling plans for sensory testing. 

Appendix 2 Definitions, terminology, and references used in sensory testing for 

petroleum taint. 

Appendix 3 Expert assessor ballot for recording sensory evaluations of seafood: 3-

alternative forced-choice (AFC) triangle test. 

Appendix 4 Expert assessor ballot for recording quantitative/qualitative sensory 

evaluations of seafood. 

Appendix 5 Trained assessor ballot for recording sensory difference-from-control 

evaluations of seafood. 

Appendix 6 Control graph for plotting and analyzing responses to triangle test for 

selection of sensory assessors. 

Appendix 7 Method for exposing live seafood to petroleum products for purposes of 

selecting and training sensory assessors. 

Appendix 8 Using random code numbers and random-sample presentation methods 

Appendix 9 Example of expert assessor training data. 

Appendix 10 Example of a Chain of Custody form and instructions. 

Appendix 11 Evaluating Expert Assessors Training Results using Fishers Exact 

Test. 
Figures 

Figure 1 Summary of sample collection, handling, and shipping 

for sensory evaluation.............................................................................8

Figure 2 Sampling kit for collection of samples.....................................................9 

Figure 3 Decision tree for sensory testing methodology.....................................27 

Figure 4 Model system solution of water-soluble fraction of petroleum 

for testing sensory assessors ...............................................................34

Figure 5 Sensory decision tree for use by expert assessors in 

evaluating petroleum taint.....................................................................59

Figure 6 Sensory decision tree for use by trained assessors in 

evaluating petroleum taint.....................................................................62 

Tables 

Table 1 Characteristics of various types of sensory assessors in general ........24 

Table 2 Summary flowchart of sample preparation and presentation............... 47
1.0 

Scope and Use of this Guideline

1.1 Introduction 

When an oil spill occurs, local seafood resources may be exposed to 

petrochemicals that affect their sensory qualities (taste, smell, and appearance). Even 

when seafood samples from the spill area pass the standard chemical-analytical tests 

(the levels of polycyclic aromatic hydrocarbons are below the limits permitted as 

determined by human health risk assessment), flavor or odor still may be affected. Taint 

in seafood renders it adulterated and unfit for human consumption according to U.S. law 

(Federal Food, Drug, and Cosmetics Act, US Code 21, Chapter IV, Sec. 402 [342], a.3). 

The specific compounds in oil responsible for causing off-flavors and off-odors in 

seafood have not been determined with certainty. Experience at recent oil spills 

indicates that, when well-trained sensory panelists conduct sensory testing, there is 

generally a high degree of correlation between the results of chemical analysis and 

sensory testing. Because this correlation is not absolute, there is a role for both sensory 

and chemical analysis in assessing adulteration and safety of seafood. Analytical 

instrumentation, particularly hand-held electronic noses, continue to advance and may 

eventually play a significant role at oil spills as tools for rapid assessment. However, at 

their present state of sophistication, these instruments are chemical detectors only, 

incapable of making any sensory judgment on odor or flavor. The final judgment about 

the presence and absence of taint in seafood (or in any food) remains the jurisdiction of 

human assessors. 

Fisheries and water researchers have conducted much valuable research on 

seafood tainting. However, the pertinent information from the many existing research 

and guideline documents needed to be pulled together and adapted specifically for 

testing seafood exposed to petrochemicals. Some of the most extensive research has 

been conducted in Aberdeen, Scotland at the former Torry Research Station. 

Individuals from this former institution have provided valuable information included in this 

guideline. In the literature, some of the most technically useful and inclusive guideline

work has been done by Environment Canada, as found in their 1997 Technical 

Guidance Document for Pulp and Paper Environment Effects Monitoring (EEM) 

1 
(Environment Canada 1997). Portions of the sensory section of the EEM document

served as a framework for writing this guideline.

1.2 Scope and Use 

The specific scope of this document is to provide guidance for conducting

appropriate sensory tests to objectively assess seafood resources for petrochemical 

taint following an oil spill. The instruction and background contained here is intended not 

only for the sensory professionals and assessors, but also for other personnel 

responsible for managing seafood. This guidance applies to finfish, shellfish/mollusks, 

and crustaceans. 

This document does not provide guidance on how to make the decision to 

conduct or not conduct sensory testing; it provides guidance on how to conduct the test 

once the decision has been made to do so. 

Seafood issues are unique to each incident. This means that sensory evaluation 

of seafood resources for petroleum taint must be area- and incident-specific, rather than 

taking a generic approach to every spill. In addition, the design and implementation of 

sensory tests for this purpose must generate results that are both scientifically sound 

and legally defensible. This guideline is meant to help ensure that sensory testing is 

appropriate to the oil spill context and is conducted with adequate and appropriate 

quality control. Once the decision to conduct sensory testing is made, it is important that 

industry and regulatory agencies immediately engage the assistance of an experienced 

sensory professional (see Section 1.3 for definition) in both designing and 

implementing the sensory-testing procedure. 

This guideline provides systematic instructions for sensory testing involving either 

of two types of assessors: 

1) Trained assessors, or 

2) Seafood product expert assessors. 

There is a detailed definition of the two assessor types below in Section 1.3. 

Each section of the document is organized according to these two assessor types, as 

procedures in the section may be different depending on the type of assessor. 

This guideline might involve hazardous materials and does not claim to address 

all of the safety concerns associated with its use. It is the responsibility of the user to 

2 
adhere to appropriate safety and health practices. The processing and maintenance of 

sensory samples should follow good manufacturing practices. 

1.3 A few words about terminology

1) The term seafood generally applies to finfish, shellfish/mollusks, and 

crustaceans. When sections of this guideline refer only to one of these classes, 

it will be specified. 

2) Tainted seafood is herein defined as “seafood that contains abnormal odor 

or flavor” based on the sensory analysis vocabulary of ISO 5492 (see 

Appendix 1). The contextual meaning of taint is an odor or flavor introduced into 

the seafood from external sources. 

This excludes any natural byproducts of deterioration due to 

aging during storage, i.e., decomposition of fats, proteins, or other components; 

or 

• 

• 

• 

• 

• 

microbial contamination normally found in fish. 

3) In the field of Sensory Science, many terms are interchangeably used to refer to 

certain personnel involved in a sensory test. For purposes of this document, the 

terms will be defined as follows: 

Sensory professional will be defined as an individual who has received a 

combination of University-based sensory science instruction and practical 

experience that provides them with the ability to design and execute various 

types of sensory studies. 

Assessor is defined as any person taking part in a sensory test, usually an 

individual who evaluates a sample for odor, taste, appearance, etc. 

Panel is defined as any group of assessors chosen to participate in a sensory 

test. Following, different types of assessors are defined in order of experience 

and level of training: 

a) A consumer is defined as an untrained, naive assessor. 

b) A trained assessor or trained panel is defined as a group of 

assessors selected and trained to perform a specific task (this may be 

for a particular product or for a particular attribute). For purposes of 

3 
this guideline, they will hereafter be referred to as “trained 

assessors”.

c) An expert assessor is defined as an assessor with a high degree of 

sensory ability and experience with sensory methodology and who is 

able to make consistent and repeatable sensory assessments of 

various products. 

d) A specialized expert assessor is defined as an individual who has 

additional experience as a specialist in a certain product and/or 

process and who and is able to evaluate the effects of variations 

related to raw materials, recipes, processing, storage, aging, etc. In 

many countries, such as the US and Canada, seafood inspectors 

(employed by either NOAA/NMFS or USFDA or the Canadian Food 

Inspection Agency (CFIA)), perform sensory testing of a wide variety 

of seafood species and processes on a daily basis as part of their job. 

In addition, most inspectors have received some education in sensory 

science methodology, and have been selected, trained and validated 

as being highly accurate and repeatable sensory assessors. These 

individuals meet the requirements of specialized expert assessors of 

seafood products. For purposes of this guideline, they will hereafter 

be referred to as “expert assessors”. 

This document provides guidance on sensory testing using either a panel of

“trained assessors” (b) or “expert assessors” (d). Further details of the differences 

in selection, training, testing methodology and numbers of assessors needed are 

addressed in each section of this guideline. 

Additionally, see Appendix 2 for a detailed list of definitions of sensory attributes 

used in this document. 

4 
2.0 

Collection and Preservation of Seafood Samples 

for Sensory Evaluation 

2.1 Introduction 

This section provides technical guidance on the collection and handling of

seafood samples for testing the sensory effects of petrochemicals on the resident finfish 

and shellfish populations. Sensory professionals should collaborate with other involved 

individuals such as fisheries biologists, statisticians, spill site managers and 

coordinators, and appropriate regulatory authorities, on planning the number and size of 

sampling sites, the number of organisms from each site to be tested, sample collection 

responsibility, and chain of custody procedures. 

See Section 2.7 for more details or Appendix 1 of this document for examples 

of sampling plans. 

2.2 Types of samples to be collected 

Several types of samples are referred to in this guideline: 

Samples generally refer to indigenous species collected from the spill area to be 

tested for the presence of taint, i.e., the “unknowns” for which the qualities of 

odor and flavor will be established. These could also include living seafood 

samples that are held in captivity in the spill area (generally in cages) to monitor 

changes in taint as the spill is cleaned up and the oil begins to weather, or in 

commercial aquaculture facilities. 

• 

• Control samples include any seafood samples taken from unaffected areas 

adjacent to the spill area to provide the "background fish flavor/odor against 

which taint in the “unknown” samples is assessed. Control samples are collected

before or at the same time as "affected" samples from the spill area and should 

be handled in exactly the same manner. They provide an internal control in the 

test design, and the data from these samples can be used to measure the 

degree to which samples from the spill area differ from background samples. 

Control samples of each species to be tested should be included in the test 

design when using expert assessors, but must be included when using trained 

assessors. When control samples are not available under any circumstances, 

5 
sensory assessments should be conducted only by expert assessors trained in 

evaluating the species in question who, therefore, have an "internal control" from 

their training and on-the-job experience. 

Concurrent samples for chemical analysis. In addition to sensory testing, it is 

sometimes decided to conduct chemical testing of seafood samples from the 

affected site. If the decision is made to conduct chemistry, the final sample size 

should include enough samples from the affected and control areas to allow onehalf of each organism to be retained for chemical analyses, and for possible 

correlation with sensory analyses. The same rapid collection and preservation 

methods should be used in handling these samples, along with the same 

thorough documentation and chain of custody, as for sensory samples. In 

addition, because organisms are usually not tainted uniformly in any 

environment, it is important to code samples so that chemistry and sensory data 

can be compared for the same organism. Chemical analyses can sometimes 

be delayed until results of sensory testing are available. 

• 

• Reference samples are used in sensory training and testing as an illustration for 

the definition of a sensory attribute or condition (such as intensity). These 

include any product that illustrates a sensory attribute or intensity and, in this 

work, may include seafood, petroleum products, other food or non-food items, 

etc. (see Appendix 2). Reference samples are chosen so that they demonstrate 

a chosen attribute and can be generated as often as needed and in the same 

“repeatable” condition. Data are not collected from reference samples, nor are 

they included in the test design for statistical analysis. 

2.3 Timing of sampling during oil spill and cleanup 

The time between exposure of an organism to spilled oil and the onset of tainting 

varies, as does the intensity and persistence of the taint (Motohiro 1983; Law and Hellou 

1999; Whittle et al. 1999). The degree of taint depends on several factors: type of 

petroleum product, habitat, water temperature, weather conditions, etc. (see Motohiro 

1983, for a review). Reported times required for onset of taint range from less than 1 

hour to 48 hours; thus samples for sensory testing should not be taken before a 

minimum 48 hour exposure period. 

6 
Control samples from areas adjacent to the spill should be taken as quickly as 

possible (no waiting period) and must be taken before the spill spreads. For obvious 

reasons, control samples and affected samples must be taken from an area as close as 

possible to the affected area to reduce background variability in natural sample odors 

and flavors. Figure 1 schematizes the necessary steps in collecting, handling, and 

shipping seafood samples from the spill site to the evaluation laboratory. 

2.4 Handling samples during and after collection 

It is of primary importance that all samples be collected to prevent any postsampling exposure to contaminants or other conditions that could affect the results or

credibility of the sensory assessments. For example: 

• Exposure to fuel or other petroleum products aboard the sampling boat 

• 

• 

Contact with packaging materials made with petroleum products 

Exposure to inappropriate holding temperatures or conditions that could induce 

the production of off-flavors or off-odors within the product 

It is essential, from the start, to ensure that all necessary steps are followed to 

demonstrate "chain of custody” (see Section 2.6.2). To be legally valid, it must be 

evident that the data were generated from samples taken from the specified areas and 

could not have been contaminated at any other point in time after sampling. 

7 
Oil Spill Occurs 

Determination made by State health agencies or other spill 

responders to conduct sensory testing 

Institute Chain-of-Custody procedures

Establish experimental design of sensory tests 

Establish number of samples to be collected - double the 

number of control and suspect samples if chemistry is to be 

performed 

Collect control samples (if able) 

Control samples 

(all species) 

Finfish Crustaceans 

(shrimp, lobsters, crayfish, 

etc.) 

Mollusks 

(oysters, clams, mussels,

etc.) 

In Field 

Collect samples, process appropriately, immediately wrap in foil, 

code, chill, and transport to laboratory. 

At Laboratory 

Prepare samples appropriately by species (see Section 2.6) 

If concurrent chemical testing, divide and code 

Re-wrap in foil, vacuum seal, code 

Chill at 0-4° C 

for immediate testing (within 

24 hours) 

Freeze at 

< -20° C 

and test within 1 month 

or freeze < - 60° for longer

Figure 1. Summary of sample collection, handling, and shipping for sensory evaluation. 

8 
2.5 Ready-to-use sampling kit 

As part of emergency preparedness, a sampling kit can be pre-assembled and 

ready for field use when an oil spill occurs. We suggest the contents of such a sampling 

kit as shown below.

Quantity for sample size n=21 

organisms

Items 

1 roll 

Heavy-duty aluminum foil - institutional rolls. 

25 Vacuum-packaging bags of a size appropriate to the species being

sampled. Pre-code if possible. 

1 Vacuum sealer (consumer model, if institutional model is not available). 

50 Zip-lock bags of suitable size, with straws for evacuating air. Pre-code if 

possible. 

6 Cutting boards (use separate boards for control and exposed samples; 

label clearly). 

6 Knives (use separately for control and exposed samples; label clearly). 

4 Scissors (use separately for control and exposed samples; label clearly). 

4 Permanent marking pens 

25 Adhesive labels

2 Coolers (1 each for control and exposed samples; label clearly). 

6 sheets Styrofoam or packing material

1 roll Newsprint (unprinted) for packing material 

2 Shipping cartons (1 each for control and exposed samples). 

weight of samples Dry ice or ice packs 

2 rolls Packing tape and/or masking tape 

Figure 2. Sampling kit for collection of sensory samples. 

2.6 Chain of custody and ensuring validity and integrity of sensory

samples 

2.6.1 Collecting seafood samples 

The EEM document (Environment Canada 1997) cites seven requirements for 

sample collection of indigenous species for exposed and control samples that can be

adapted to sampling during oil spills. 

1) Both exposed and control samples must be collected from the same water 

body and similar habitat type. Though the EEM document applies to 

collecting from smaller freshwater areas, the same principle holds true in 

marine sampling. This reduces any variability in flavor caused by seafood 

samples originating from dissimilar habitats. 

9 
2) The same collection methods must be used in obtaining both exposed and 

control samples, and organisms must be removed from the water as quickly 

as possible after capture.

3) Organisms collected in the control area must be physically isolated from the 

exposed population to prevent any mixing of the two groups.

4) Exposure times for organisms collected in the exposed area should be at 

least 48 hours; to ensure that uptake of oil has reached its maximum. 

5) Standard measurements, such as weight, length, sex, and age, must be 

recorded for each organism collected for sensory testing. If possible, steps 

may be taken to preserve the otolith for age determination. 

6) Organisms taken from each exposed and control area should approximate the 

same size, age, and sex ratio. If trained assessors are used, the weight 

range among organisms should not exceed a factor of 1.2 to minimize 

potential differences in texture, color, and flavor. This is not an issue for 

expert assessors, providing sample sizes are large enough to allow multiple 

assessors to evaluate them. 

7) Only organisms that are alive at the time of collection should be used for 

testing to ensure that they have been exposed to taint conditions. This also 

ensures that there are no flavor effects from decomposition present, as fish 

can deteriorate while still in the water if they die in the net (EEM and ASTM 

documents, see Appendix 1). Any quality (freshness) evaluations must be 

performed only by trained inspectors or expert assessors. 

2.6.2 Ensuring chain of custody (continuity of evidence) 

During sample collection and preparation for transport, the handlers must be able 

to account for all aspects of handling in case they are called to testify in legal 

proceedings (see part 2 of Appendix 10 for a definition and detailed list of procedures). 

Complete documentation must be demonstrated through detailed note-keeping, 

including the time of all significant events, where event occurred, what happened, who is 

present, etc. This also includes being able to swear under oath as to the location of the 

samples from the moment they are collected until the samples are delivered to a specific 

individual at the sensory testing laboratory. From that point on, chain of custody 

becomes the responsibility of the sensory testing laboratory (although, in some cases, 

10 
the individual who supervised the sample collection may be the same person 

responsible for sample storage and preparation at the laboratory). 

Ensure security of the sample at all times. If the samples are left untended for 

any period of time, (e.g., while being held in chilled or frozen storage), they 

should be locked in an appropriate container and a seal placed around the 

opening with a signature to show that the container was not disturbed (opened). 

An example of this would be holding the samples in a cooler, with the lid taped 

around to completely seal it into place and with signatures of the responsible 

person on the tape or seal. 

• 

• 

• 

• 

• 

• 

• 

• 

• 

Record the identity of every person who has custody of the samples at any point 

in the sequence, and include an NRDA-style chain-of-custody form. This number 

should be kept to a minimum with the ideal number being one individual (or, at 

the most, two), as each individual may possibly be required to testify as to the 

sample security. 

Each party involved should record the time and other pertinent details, such as 

when samples are transferred from individuals and locations. 

Record the location and environmental conditions under which samples are held 

throughout the entire history, e.g., temperatures for chilled or frozen samples. 

An example of a chain of custody form and related instructions are included in 

Appendix 10. 

2.6.3 Secure shipping of frozen samples. 

If sensory testing cannot be performed within a 24-hour period, samples should 

be frozen according to procedures specified in Section 2.8. Instructions are given here 

for the secure transport of frozen samples to the sensory laboratory. It is imperative that 

chain of custody be maintained during this process. 

Samples should not, at any point, reach a temperature above -20° C during 

shipping or storage. 

Initially, all seafood samples should be wrapped in aluminum foil to ensure no 

contact with petroleum-based packaging materials. 

The foil-wrapped samples should then be vacuum-sealed and then over-wrap 

again with heavy-duty aluminum foil. Make sure each sample is clearly labeled. 

Place clear, odor-free shipping carton lined with thick Styrofoam and packing 

material in the freezer to chill before adding the samples. 

11 
Dry ice or ice packs will be added to the shipping carton with no less than a 2:1 

ratio with samples. Alternate layers of sample with layers of ice packs or dry ice. 

The box should be as tightly packed as possible to exclude as much air as

possible. Pack with unprinted newspaper (i.e. clean, never exposed to ink) or 

with Styrofoam chips to fill the air voids. As many air voids as possible should be 

excluded to maximize the frozen stability of the samples. 

• 

• 

• 

• 

• 

Seal package tightly, keeping in mind the requirements for chain of custody (i.e., 

securing and signing the closures so that evidence of any tampering will be 

clearly apparent). If possible, photograph the sample containers prepared for 

shipping. Ship immediately via secure transport. Package should not be en 

route more than 24 hours. 

Upon receipt of the sample container, examine it for security of contents, i.e., any 

evidence of tampering, and document condition of container. If possible, 

photograph the sample containers on arrival. Then, open the container, remove 

samples from extra packing material, but retain vacuum packaging and 

immediately place in secure freezer at -20° C or lower. Examine samples for any 

signs of thawing and document accordingly.

2.7 Statistical sampling requirements 

The numbers of each species that should be collected from any given area for 

purposes of sensory testing depends on: 1) the population size of the species and the 

size of the affected area (calculated according to the best-available information) or, 2) 

on the minimum number required that will give a sufficient quantity of sample for testing. 

The assumption is always made that there will be some variability in uptake of taint 

within a species when exposed to the same tainting conditions. 

There are two considerations in establishing the number of samples required for 

testing: 

2.7.1 Basic types of statistical sampling plans 

Attribute Each sample unit is classified according to conformity. 

Variable Characteristics are evaluated on a numerical scale. 

12 
For an oil spill situation, attribute-sampling plans are recommended. Thus, if a 

sample is tainted, it is non-conforming. 

For attribute sampling guidelines, refer to the 1994 U.S. Code of Federal 

Regulations, Title 50; the 1993 ANSI/ASQC attribute sampling procedures; the UN/WHO 

Codex Alimentarius Commission sampling procedures; and the ISO attribute sampling 

procedures. See Appendix 1 for complete citations. 

2.7.2 Required sample sizes and presentation for sensory testing 

• 

• 

• 

– 

– 

At least 6 samples per species from each area are recommended for testing with 

either type of assessor. As a general rule, the sample size collected should 

comply with the minimum requirements in the statistical sampling tables of ISO, 

Codex Alimentarius, CFIA, and NOAA (see Appendix 1). If samples are to be 

collected concurrently for both sensory and chemical analyses, the sample size 

should be doubled to ensure sufficient samples.

For testing by expert assessors: A sample will consist of an individual organism 

when testing finfish and lobsters, or multiple organisms when testing shellfish. 

Depending on the size of the shellfish, 3 to 6 organisms are recommended for a 

sample. 

When using trained assessors: Samples can be presented in one of two ways. 

20-g blended, individual fish samples (BIFs) from multiple pooled 

organisms, or 

20-g dorsal-muscle single-organism samples (see Environment 

Canada 1997). Given the expected recovery of fish or shellfish flesh 

(see table below), you will need to compute the total weight of the final 

sample and the estimated number of samples needed. 

Type of 

seafood 

Expected % recovery

of edible flesh

Finfish 38–40

Flatfish 30–33

Lobsters 14–18

Shrimp 28–30

Clams 16–20

Oysters 25–30

Scallops 20–25

Mussels 15–20

13 
2.8 Species-specific collection procedures 

Samples must be obtained for each commercial species normally harvested from 

the area that is suspect. Generally applicable instructions for all samples should be: 1) 

handle in a manner that ensures that no interfering odors/flavors of decomposition are 

allowed to develop that could interfere with the evaluation of flavors from contaminants, 

2) do not expose to products of petrochemical origin that might interfere with the 

integrity of the sample under chain of custody. The goal of these methods is to 

immediately stabilize the harvested seafood samples. The important factors are 

cleaning, protecting from exposure to air, and chilling. Following are the general 

requirements for each type of seafood. 

2.8.1 Finfish 

Samples should be taken from the water source using clean gear, not previously 

exposed to petroleum from any source. 

Seafood samples are rinsed in clear, potable, odor/flavor-free water to remove 

any residual surface oil (if necessary, suitable bottled water can be brought to the 

sampling site). 

• 

• 

• 

• 

Samples are to be prepared in the same manner as for commercial sale. Clean 

to remove viscera, gills, and kidney if this is done in commercial practice. Under 

no circumstances should the viscera come into contact with the flesh that will be 

used for sensory evaluations. The head should be left on but the gills removed 

carefully to preserve the otolith if it will be examined for age determination. 

Carcasses must be rinsed in clean water, such as distilled water or other clean 

potable water source, and immediately placed on non-chlorinated ice with the 

body cavity facing downward to allow for drainage. Use enough ice so that the 

sample does not come in contact with drainage or melt water. 

After draining, samples should be tightly wrapped in double layers of heavy-duty 

aluminum foil and then individually placed in double zip-lock bags, evacuating as 

much of the air as possible by pushing it out or by sucking it out through a straw. 

Ensure that no plastic touches the sample. Ideally, the samples should be 

vacuum-sealed if they are to be frozen (several home models are available). 

14 
Samples must be clearly labeled with all pertinent information regarding sampling 

sites, dates, etc. (see Section 2.6.2). All labeling should be firmly and securely 

affixed to the plastic outer-wrap of the samples. 

• 

• 

• 

• 

• 

Either chill samples to 4o C and test within 24 hours, or freeze samples 

immediately and store at a temperature of at least -20o F (preferably -30o F). 

Frozen samples must remain frozen at all times during shipment from the field to 

the sensory-evaluation laboratory, or well iced if the testing will be done within 24 

hours. 

Samples should be tested as soon as possible and not kept frozen for more than 

1 month before testing. (However, with proper handling and < - 60o F storage, samples 

can be saved for longer periods and used successfully to demonstrate the presence of 

taint.). To maximize ease of data presentation, we recommend shorter rather than 

longer storage times. If samples are to be in frozen storage and are not vacuum-sealed 

in the field, they should be vacuum-sealed upon arrival at the sensory-evaluation 

laboratory as described above in this section. 

2.8.2 Crustaceans and molluscan shellfish 

Ideally, a suitable sensory laboratory would be available near the spill site so that 

crustaceans and mollusks can be evaluated alive, as they would be just before cooking 

by the consumer. If this is not the case, samples are to be shipped alive or frozen to the 

evaluation laboratory as described below.

The goal of these methods is to immediately stabilize harvested shellfish to 

prevent any changes due to deterioration that could interfere with the evaluation of 

petroleum-related flavors and odors. The important factors are cleaning, protecting from 

exposure to air, and chilling with ice (if samples are to be tested alive) or by rapid 

freezing if live testing is not possible.

Samples must be rinsed in clean, potable, odor- and flavor-free water (e.g., 

distilled or filtered) to remove any residual surface oil and immediately placed on 

non-chlorinated ice. Sufficient ice should be used to keep samples from coming 

in contact with melt water. 

Samples should be coded in the field with unique 3-digit random numbers (see 

Appendix 8) and labeled with all the pertinent information. 

15 
Samples that can be evaluated alive should be tightly wrapped in double layers 

of heavy-duty aluminum foil and placed on ice in clean, odor-free shipping

containers. 

• 

• 

• 

• 

Samples that must be shipped frozen for evaluation should be wrapped 

individually in double layers of heavy-duty aluminum foil, and frozen at -20o C, or 

lower for about 30 minutes to immobilize the sample (i.e., lobsters, crab). They 

are then placed in double zip-lock bags with as much of the air evacuated as 

possible by pushing or sucking it out through a straw, ensuring that no plastic 

touches the sample. Ideally, samples should be vacuum-sealed before freezing. 

Samples must be clearly labeled with all pertinent information required coding 

each sample for later analysis at the sensory-evaluation laboratory. All labeling 

should be firmly and securely affixed to the plastic outer-wrap of the samples. 

Again, all appropriate measures must be taken to ensure chain of custody 

throughout the handling and transportation steps. 

16 
3.0 

Selecting Appropriate Sensory Test Methods and Assessors 

3.1 Introduction 

Because of the legal and regulatory implications of oil spills, it is strongly 

suggested that the sensory evaluation of seafood be designed and conducted under the 

direct supervision of a trained professional, in this case a sensory scientist. Most

importantly, consideration must be give to the amount of information that interested 

parties will require and the types of assessors that are available. The level of necessary 

assessor training and the extent of information that can be collected will vary according 

to the selected test method. 

3.2 Subjective vs. objective sensory testing

Sensory evaluation in general can be either subjective (consumer) or objective

(analytical). Some key differences in subjective vs. objective sensory test methods 

include: the type of assessor used (untrained vs. trained), types of information collected 

(personal feelings vs. product attributes and intensity), and numbers of assessors

needed (many vs. few). When evaluating any food for the presence of taint, in this case 

seafood, the evaluations must be objective. 

3.2.1 Subjective testing 

Subjective testing measures responses as feelings and preferences about 

samples. Untrained assessors on this type of consumer panel provide purely 

subjective responses—based on personal bias—which are not appropriate for taint 

analysis. Subjective sensory evaluation measures an assessor’s feelings toward a 

sample; it does not measure the sensory attributes of the sample. Thus, subjective 

testing is clearly NOT appropriate for assessments of taint upon which decisions to 

close/reopen fisheries may be based. These kinds of decisions call for objective, 

analytical sensory evaluation to confirm and quantify the presence of taint (York 1995). 

17 
3.2.2 Objective testing 

Objective sensory testing measures the intrinsic sensory attributes of 

a sample through the analytic sensory perceptions of trained human assessors (Jellinek 

1985; Meilgaard et al. 1999). Several objective test methods would be suitable for 

assessing the presence of seafood taint. 

3.3 Selecting a sensory testing approach – general considerations 

3.3.1 What answers are required? 

From the start, interested parties, working with a sensory professional, must 

decide what they want to know – what questions do they want answered so that the 

appropriate test method can be selected. Each test method requires different: 

• numbers of assessors

• 

• 

• 

• 

assessor training periods

data collection methods 

repetitions of the test 

sample numbers 

Difference testing will result in basic information that would answer the question 

“is there a difference between the suspect and control samples?” but does not provide 

information on the nature or the degree of the difference. More sophisticated testing,

such as descriptive analysis may answer many questions such as; “Is there a difference 

What is the difference? How big is the difference? Is the difference due to petroleum 

taint? How intense is the taint? What is the description of the sensory characteristics of 

the taint?” In general, the tests that give you more information about the samples require 

greater assessor training periods, but less numbers of assessors, test repetitions, and

sample quantity. These methods will be further explained in this section. 

3.3.2 Assessor type 

Objective sensory measurements are obtained from the following three types of 

trained assessors: 

1) Assessors screened and selected for sensory tasks (usually 25), 

18 
2) Assessors selected and highly trained to participate on a panel for specific 

sensory tasks (usually 10 to 15), 

3) Expert assessors, e.g., product specialists, seafood inspectors (usually 1 to 

5) (York & Sereda 1995). 

As the list of assessor types progresses above, the level of training and 

experience increases which then increases the amount of information that that may be 

obtained from the test. To conduct any objective sensory analyses of seafood (or any 

product), assessors must be 

• selected according to their abilities to perform the sensory tasks at hand, 

• 

• 

trained in the application of the required test methods, and 

monitored (validated) for their ongoing abilities to effectively perform the 

sensory tasks. 

Assessors are chosen to work within specific test protocols and must be trained 

to perform within those criteria (see Table 1). Assessors must be considered the 

analytical tool for the assessment for the presence of taint. 

3.3.3 Numbers of assessors required 

In general, the higher the level of training, the less statistical variability in the 

sensory data and the fewer the number of assessors required. (Note: This is why very 

large panels, of 100 or more assessors, are required for subjective (consumer) testing. 

Because their responses are personally biased, there is wide variability within and 

among the resulting data sets.) 

In many cases, the type and number of assessors available (professionals, 

expert/trained, new trainees) limit the feasibility of testing approach that can be 

implemented. 

3.3.4 Assessor availability

In reality, the limiting factor in choosing a particular sensory test method following 

an oil spill is often the type of assessors available, given the urgency and often remote 

locations of spill scenarios. With this in mind, two types of assessors that are 

recommended are: 

19 
Expert assessors can specify the presence and intensity of petroleum 

contamination, as well as the presence of flavor changes that are not due to taint (i.e. 

quality changes due to autolytic and/or microbial decomposition). 

Trained assessors can measure the degree to which samples differ from 

standard, uncontaminated samples for the presence of taint. Because this group is not 

trained in assessing general seafood quality, we cannot assume that they will 

differentiate petroleum taint from other quality changes, caused perhaps by

deterioration, that might be present in seafood with low or borderline levels of taint. For 

this reason, it is even more essential when using trained assessors that control samples 

and taint samples be handled and processed quickly to prevent extraneous flavor 

changes. 

3.4 Test selection 

3.4.1 Discriminative testing 

Discriminative testing is also referred to as difference testing. Several different 

sensory test methods will allow one to determine differences. The 2 types of test below

are appropriate for taint assessment. 

3.4.1.1 Difference testing using the Triangle Test 

In early studies to measure the effects of petrochemical exposure on fish flavor, 

one of the sensory-evaluation methods used is difference testing using the triangle test. 

Here, an assessor is presented with three coded samples—two of which are the same—

and is asked to identify the "odd" sample. This is known as the 3-alternative forcedchoice triangle test. 

There are problems, however, in using the triangle test to establish the presence 

of petrochemical taint. 

The procedure is used to determine any perceptible sensory difference between 

samples of two products; thus, all differences—not just the presence of 

petrochemical taint—will be used by the assessor in evaluating the samples 

(e.g., color, texture and other flavor differences which may not be taint). 

• 

• Actual differences among samples may be detected in a single sensory attribute 

or in several attributes. 

20 
Although applicable when the nature of the difference is unknown, this test does 

not determine the magnitude or direction of difference; also, assessors must be 

trained to identify the attribute responsible for the difference.

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

The test is applicable only if the products are homogeneous, and does not 

account for natural variations in the product, such as those found when working 

with seafood. 

Because the test identifies only a difference, and not the magnitude of the

difference, the data cannot be compared over time, such as when the effects of 

the petrochemical exposure begin to abate. 

Triangle tests require a relatively larger quantity of sample than the 

recommended test. 

3.4.1.2 Difference-from-control (DFC) testing 

The DFC test is recommended for use with trained assessors, and sometimes 

expert assessors in assessing petroleum taint in seafood flesh (ASTM E 1810-96; 

Appendix 1). This test is often used in quality-control situations to measure a difference 

and estimate the size of any difference found, taking into account the natural variability 

of the product. The advantages of this method include: 

provides an estimate of the presence and degree of difference compared to a 

clear control; 

defines more easily the nature of the difference;

assessor is less influenced by other factors in the sample, e.g., natural flavor of 

the seafood and intra-species flavor differences among samples from different 

areas; 

data collected can be analyzed through standard statistical tests; 

test recognizes that seafood, being natural foods, have some variation in flavor 

and this natural variability is considered in the experimental design and the 

statistical analysis; 

comparisons between the triangle and DFC tests show a high frequency of false 

statistically significant results (Type I error) in the triangle test (Aust et al. 1985). 

21 
3.4.2 Descriptive Analysis Testing 

Descriptive analysis is a sensory method by which the attributes of a food or 

product are identified and quantified, using human subjects who have been specifically 

trained for this purpose (Manual on Descriptive Analysis Testing for Sensory Evaluation, 

ASTM Manual Series: MNL 13, 1992). Most of these methods require the use of highly 

trained assessors and evaluate many sensory attributes within each sample (York and 

Sereda, 1995). For taint assessment, panelists can be trained to provide both qualitative 

and quantitative information on the presence of petroleum taint only. In petroleum spill 

or environmental effects monitoring situations intensity (quantitative) data may provide 

valuable information to the interested parties if the problem persists for long periods of 

time (Whittle et al. 1997).

3.4.3 Testing with Product Experts and official inspections 

The International Organization for Standardization (ISO), Technical Committee 

34 on sensory analysis, sub committee 12 has accepted the role of the expert assessor 

in product evaluations (see ISO/DP 8586 Sensory Analysis - Assessors, Part 2 - General 

Guidance for the Selection, Training, and Monitoring of Experts). Experts contrast with

other types of assessors in the level of training that they must have in both product 

specialization and sensory analysis methods, and also in their responsibility for samples, 

testing conditions, data analysis, and reporting of results (York and Sereda, 1995). This 

awareness of the need for expert assessors’ seafood evaluation for international trade

has been demonstrated by Codex Alimentarius in a Code of Practice for the Sensory 

Evaluation of Fish and Fish Products (see Appendix 1). 

Government agencies routinely use seafood product experts to inspect seafood. 

These inspectors undergo years of training and direct product experience and may 

easily be further trained to detect the presence of taint, such as from an oil spill. These 

assessors use either a pass/fail or a grading system, but, in either case, seafood that is 

tainted or unwholesome is considered not fit for consumption or trade and will not pass 

an inspection. 

22 
3.5 Selecting an assessor type

3.5.1 Two types of assessor panels appropriate for seafood taint 

assessment 

Panel of 3 to 5 expert assessors (fish inspectors, usually employed by a 

regulatory agency) whose job it is to assess fish for its suitability for sale for 

human consumption. These assessors must be selected for and have additional 

training to detect petroleum taint in seafood. 

• 

• Panel of 10 to 15 selected and trained assessors convened specifically for the 

task of assessing taint from a particular oil spill. 

The capabilities of different types of assessors and the advantages and 

disadvantages for taint assessment in particular are compared in the following table [see 

also ISO 8586-2:1994(E); see Appendix 1]. 

23 
Table 1. Characteristics of various types of sensory assessors in general. 

Type of 

 Test 

Type and definition of 

assessor 

Characteristics of assessors and

numbers needed

Possible advantages of

using such assessors

Consumer Tests Untrained, naive assessors 

chosen to represent market 

segment. 

Untrained - Respondents relate 

feelings, wants and needs of 

products. 

Need at least 100 respondents. 

Not appropriate for taint 

assessment. 

Discriminative 

Tests 

Selected and trained 

assessors who have been 

screened and selected for. 

Chosen for his/her shortterm ability to perform a 

sensory test. 

Assessors work under supervision 

of a sensory professional and 

perform short-term tasks such as 

difference testing and scaling. 

Need approximately 25 

respondents. 

More readily available, esp. 

in remote areas. 

Only spill-specific training is 

required. 

Descriptive Tests Assessors who have been 

screened and selected for 

and extensively trained for 

long term tasks. 

Experienced assessors who also 

work under the supervision of a 

sensory professional. 

Consistency of judgment, both 

within and among testing sessions. 

Can provide detailed quantitative 

and qualitative information 

Need 10-15 respondents. 

Fewer assessors required to 

maintain a given degree of 

reliability in the results. 

Long-term sensory memory

and accumulated 

experiences allow

recognition of particular 

attributes, such as taints. 

Tests using 

Product Experts

as assessors

Assessors with high degree 

of sensory sensitivity and 

well experienced with 

sensory methodology. 

Specialized experience with

the product and/or the 

process and/or marketing 

and can make consistent 

and repeatable sensory 

assessments. 

One who can evaluate or 

predict effects of variations 

relating to raw material, 

recipes, processing, storage, 

aging, etc., of various 

products. 

Long-term sensory memory. 

Can operate independently. 

Extensive experience in the 

relevant specialist field. 

Highly developed ability to 

recognize and evaluate sensory

properties. Mental retention of

reference standard. Recognition of 

key attributes. 

Can apply deductive skills to 

problem solving and can describe 

and communicate conclusions or 

take appropriate action. 

For taint assessment, 3 to 5 

respondents are recommended. 

Evidence from an expert 

panel is more persuasive, for

example, in a court of law.

A product expert assessor 

takes full responsibility for all 

judgements, comments and 

estimates, including tasks 

undertaken by a panel 

leader. 

Gives advice on sensory 

aspects of contractual or 

legal matters. 

24 
3.5.2 Recommended assessor types 

3.5.2.1 Expert assessors 

Expert assessors are most preferable because they are trained, experienced, 

and validated (sometimes certified) in assessing seafood products. Trained assessors 

will require years of more training to achieve the same goals. Expert assessors must be 

further selected and trained specifically for petroleum tainted seafood (see Section 1.3). 

If sensory results indicate that commercial seafood resources are tainted, it may 

have economic implications to individuals and industries for extended periods. 

Considering both the potentials for damage claims by affected parties and the 

speed with which the spill response must be handled, we recommend that, when 

possible, expert assessors be chosen. These inspectors are already familiar, 

through their training and experience, with the sensory attributes of taint. 

Seafood inspectors are employed by government agencies and assigned to 

specific offices and laboratories in different areas of the country. By prior 

agreement with their employing agencies, arrangements can be made for 

temporary assignments of these seafood inspectors to oil spill-related sensory 

analysis in an emergency situation. This means they can travel to the spill area 

or sensory laboratory on short notice and immediately begin assessing spillrelated taint of seafood stocks. The presence of a defect can be quantified by 

these inspectors, as in seafood inspections carried out under U.S. federal law 

where defect levels are established. 

• 

• 

• 

Although seafood inspectors are experienced in assessing all aspects of quality 

deterioration in seafood, we recommend that the sensory testing methodology be 

designed to generate additional data other than in routine inspections (see

Section 8.3). The first step in this testing should be to re-familiarize (recalibrate) 

the inspectors with the sensory attributes and intensity of petroleum 

contamination. 

Canada's approach to sensory testing differs in that descriptions of defects

under the categories tainted, decomposed and unwholesome are given by law. 

Also, a defect is defined as perceptible at the level of “distinct and persistent,” in 

other words, a flavor or odor that may be present at a very low level, but that 

does not disappear when left to stand for 1 minute. 

25 
3.5.2.2 Trained and monitored assessors 

Trained and monitored assessors are the other choice for objective sensory 

evaluation. Ten to 15 individuals are selected according to their consistent ability to

perceive taint at normal levels, and then trained for these assessments. Using trained 

assessors requires the constant application of a sensory test with samples relative to a 

known, clear, control standard, for presence of a defined difference, e.g., the differencefrom-control (DFC) test. In addition, when using trained assessors, every aspect of the 

training and testing must be conducted in the light of potential regulatory and legal 

impacts and the reliability of the evaluation results. Time and resources must be 

allocated to monitor and validate the performance of trained assessors to ensure that the 

data produced will be allowable in court, if required. 

3.6 Criteria for selecting expert and/or trained assessors

To be selected either as an expert assessor or for a trained assessor panel, 

candidates must meet the following qualifications: 

1) Basic sensory acuity and the ability to describe perceptions analytically (i.e., 

not influenced by personal bias). Allergies to seafood or to some food additives should 

eliminate a candidate assessor. 

 2) Potential to develop analytic capability through familiarization with test 

procedures, to increase ability to recognize and identify sensory attributes in complex 

food systems, and to refine sensitivity and memory so that the assessor can provide 

precise, consistent, and standardized sensory measurements that are reproducible. 

3) Capable of being monitored (validated) through frequent, periodic evaluations 

of the performance and consistency of his/her sensory-analysis decisions. 

3.6.1 Time required to assemble a panel of assessors 

If expert assessors have been previously trained for petroleum taint, they will 

require 4 to 6 hours on the day prior to sensory testing to re-calibrate. For trained 

assessors, the best scenario would be to have a previously trained and recently 

validated panel available. Assuming that a specific petroleum taint panel of trained 

assessors does not already exist, approximately 3 weeks will be needed prior to sensory 

testing to recruit, select, train, and validate a panel of assessors. See Figure 3 for a 

decision tree for selecting sensory testing methodology.

26 
Oil spill occurs in area of fish populations (commercial or sport fisheries) 

YES 

• Sensory testing required to confirm 

presence of taint for fish to be released 

for use as food. 

• Species concerned: applies to all finfish, 

shellfish, mollusks and crustaceans 

• Samples taken: see Section 3.0

• Panel type available: 

NO

Sensory testing not required 

Expert Assessors Selected Trained Panel 

Assembling the Assessment Group 

Identifying Appropriate Group at Testing Site OR 

Selecting Testing Site Based on proximity and on 

availability of appropriate group 

Preliminary validation using known samples, 

reference standards, laboratory-exposed

samples 

Selection Tests using Sequential Testing to Validate 

ability of assessor for participation 

(see Section 4.0) 

Evaluation of suspect samples for presence 

and intensity of taint using sequence: 

Raw odor – Cooked Odor – Cooked Flavor 

Training using known samples, tainted samples, 

reference standards, laboratory-tainted samples 

Raw odor 

Data Collection using Difference from Control Test to 

measure the presence and degree/intensity of taint 

present (cooked odor and flavor) 

Yes

Stop testing-Taint 

present 

No

Continue testing Data analysis to demonstrate the relationship of 

exposed samples to control samples 

Cooked odor 

Yes 

Stop testing 

Taint present 

No

Continue Testing 

Criteria established for test: 

Cooked Flavor

Yes

Stop testing 

Taint present 

No

Stop Testing

No taint present – 

samples pass

Samples demonstrate 

taint in sensory testing 

Samples do not 

demonstrate presence of 

taint 

 

Figure 3. Decision Tree for Sensory Testing Methodology. 

27 
4.0 

Selecting, Training, and Validating Sensory Assessors 

In order to conduct objective sensory analyses of seafood, assessors must be: 1) 

selected for their ability to perform the sensory task required, 2) trained in the application 

of the required test method, and 3) monitored (or validated) for their ongoing ability to 

effectively perform. Assessors are chosen to work within specific test protocols and 

must be trained to perform within those criteria. The level of training needs vary with the 

test method, the assessor type, and the form of data analysis that will be used. 

In general, the higher the level of training which has been given (as in expert 

assessors), the less statistical variability in the sensory data and the fewer number of 

assessors required. Also note – in addition to performance, availability should be a 

factor in selecting assessors, as they may be required to travel to a laboratory or spill 

site for several weeks. 

4.1 Expert assessors 

4.1.1 On-site validation 

Generally, expert assessors are already employed as seafood sensory analysts 

and routinely perform overall quality evaluation of seafood products, including taint 

(Reilly and York 1994), so are already trained. In addition, many government sensory 

analysts in the US and Canada have received training specifically for petroleum taint in 

seafood. These individuals should be chosen when possible. 

Expert assessors should be re-validated on-site for their ability to perform the test 

in case the test results are used in litigation. This validation can consist of a series of

sequential tests (as would be used for screening panelists for sensory training), and 

demonstrates that the individuals have the sensory abilities to perceive the sensory 

attributes for which the samples are being examined, and it serves to re-familiarize or, 

re-calibrate the assessor. 

4.1.1.1 Sequential testing 

The groups of tests that fall under the heading of sequential testing are actually 

difference tests that are used with pre-set statistical criteria. They allow the decisions 

28 
“accept for panel," “reject for panel,” or “continue testing” to be made via a pre-set 

graphic representation of the statistical criteria (see Appendix 6). The benefits of 

sequential tests, as described in the sensory literature (Amerine et al. 1965, Munoz et al. 

1992; Meilgaard et al. 1999), are that they “economize” on the number of tests needed 

to "accept" or "reject" a candidate, yet they also provide a statistical basis for 

accept/reject decisions. Sequential testing is based on pre-selecting the statistical levels 

of α and β probabilities for the performance level of the assessors using difference tests 

such as triangle, duo-trio, and paired comparison-difference. The test is conducted 

using a minimum of 6 sample sets to begin and continuing until the results from the 

assessor being tested moves into the accept or reject range of the control chart (see 

Appendix 6). 

4.1.1.2 Triangle test 

In this type of situation, the triangle test can be used effectively, as there is 

adequate control over the nature of the treated and control samples. Control charts for 

these tests and probability levels can be calculated using the methods described in

Meilgaard et al. (1999). As mentioned above, sequential testing using the triangle test or 

other difference tests requires the calculation of control graphs to evaluate the 

performance of each assessor candidate. The criteria used in calculating the control 

graphs (see Appendix 6) are based on the type of test used and the levels of statistical 

significance chosen. The recommended levels of statistical significance are α=0.05 and 

β=0.05. 

Samples that can be used for selection of expert assessors include: 

• tainted seafood from prior field sampling or laboratory exposures; 

• 

• 

an appropriate model system using either seafood flesh or water as the carrier 

and appropriate dilutions of critical compounds identified in the petroleum watersoluble fraction; 

concentrations chosen should represent a level of difficulty appropriate for the 

taint tested.

The recommended procedure is the 3-alternative forced-choice (AFC) triangle 

test. The three samples always include two controls and one treated sample. This 

29 
minimizes carry-over effects and increases the chance of being able to detect the 

different sample (thus increasing the sensitivity of the test). 

The sample sets are presented in the triangle test format, and the resulting 

correct/incorrect responses plotted on the control chart shown in Appendix 6. The 

samples to be used should be standardized according to the concentration range of 

stimulus that might be expected in the final testing. When the triangle test is being used, 

the samples used in selection must be homogeneous in nature and demonstrate no 

other differences except for the tainting mixture. 

4.1.2 Training expert assessors 

Specific details on training expert assessors in general can be found in the ISO8586-2 document referenced in Appendix 1. For evaluation of seafood for presence 

petroleum taint, expert assessors are trained with known (tainted and non-tainted) 

seafood samples. The ballot used in the US is illustrated in Appendix 4. The same 

ballot used for final testing is used for training. All expert assessors must demonstrate 

that they are evaluating the known samples appropriately. Data are collected and 

analyzed statistically either by a. the analysis of variance of the taint intensity data or, b. 

by Fisher’s exact test applied to the pass/fail decisions (see Appendix 11). Analysis of 

variance is the preferred method of data analysis. If analysis of variance is used for data 

analysis, there must be no assessor by sample interaction. 

For expert assessors, there is a 3-tiered approach to evaluating each sample as 

summarized below and explained in further detail in Section 7.0. 

The test for RAW ODOR is sequenced as follows: 

1) Coded samples of fish are presented for analysis of the raw odor. 

2) Assessors decide whether samples “pass” or “fail”, based on presence of 

taint (any presence causes a sample to fail). 

3) Intensity of taint is rated on the scale provided, from none (0) to strong 

(3). Any comments regarding the nature of the taint (descriptors) are also 

recorded. 

4) If taint is detected in the raw-odor test, then testing stops there, if no taint 

is detected in the raw state, then the sample is cooked. 

30 
The test for COOKED ODOR is sequenced as follows: 

1) The sample is cooked following standardized sample-preparation 

instructions for steaming or microwaving. 

2) Odor of the cooked sample is assessed using the same ballot. 

3) If taint is detected, then testing stops there, if not, the test proceeds to 

evaluation of cooked flavor. 

4) Intensity of taint is rated on the scale provided, from none (0) to strong 

(3). Any comments regarding the taint are also recorded. 

The test for COOKED FLAVOR is as follows: 

1) If no taint is detected in the cooked-odor test, the flavor of the cooked 

sample is assessed following the instructions for product testing given in 

Section 7.0. 

2) If no taint is found at this point, the sample is considered "Clear". 

Further details of expert assessor test instructions and evaluation criteria can be 

found in Section 7.2. 

4.1.3 Monitoring expert assessors 

The test method for monitoring is identical to that used for training. Known, clear 

samples are included as controls to monitor the performance of the expert assessors. If 

available, known samples prepared by laboratory exposure or by spiking may also be 

used as controls. Spiking may not produce the same sensory properties as live 

exposure in a laboratory or real spill situation. 

4.2 Trained assessors 

4.2.1 Selecting assessor trainees 

The selection of assessors for a trained sensory panel is conducted using the 

triangle test as described above for expert assessors. The selected, trained panel 

consists of 10 to 15 panelists. 

31 
4.2.2 Training assessors 

Specific details on training expert assessors in general can be found in the ISO8586-1 document referenced in Appendix 1. For an oil spill situation, assessors can be 

trained using the difference-from-control procedure, as shown on the ballot in 

Appendix 5. The control is always a clear sample of the same species, identified by

marking it “C” or “Control.” All other samples are presented with three-digit codes to 

mask their identity. 

Known samples are used for training (see ballot shown in Appendix 5). 

Panelists are instructed to follow the instructions on the ballot and to use tasting 

procedures outlined in Section 7.3. In training, data from the known samples are 

collected as blind-coded samples in the test included in the data analysis (using analysis 

of variance). Assessor performance is measured by the main effects and the assessor 

by sample interaction. There should be no statistical significance for either of these. 

Any panelist found to be assessing samples differently from the other selected 

assessors must be dropped from the panel and replaced by another trained panelist. If 

a statistician is not available, refer to Post, Mackie, Butler and Larmond, 1991 for a 

simple description and example of calculation of 1-way or 2-way analysis of variance 

(i.e. one main effect or 2 main effects). 

4.2.3 Monitoring trained assessors 

Trained assessors are monitored by including known, clear reference samples 

presented with the tainted or suspect samples. If available, known samples prepared by 

laboratory exposure or by spiking may also be used as coded samples for monitoring 

purposes. Again, spiking may not produce the same sensory properties as live 

exposure in a laboratory or real spill situation. 

4.3 Experimental design and data analysis for testing assessors 

(both expert and trained assessors) 

Data collection for taint analysis must allow appropriate statistical methods to be 

used to interpret the results. Data should include: 

descriptive statistics of the number of samples and the numbers that 

demonstrate taint. 

• 

32 
statistical analysis of the data, including variables such as species, location, 

panelists, etc. 

• 

• 

• 

• 

• 

• 

mechanism for monitoring the performance and consistency of the experts 

and/or trained assessors, for the purpose of demonstrating the effectiveness of 

the measurement tool. 

comparisons of samples of affected area against control samples. 

When possible, the experimental design should be done with the advice of a 

statistician. Studies should be conducted, as much as possible, as a randomized, 

complete block design to allow for simple analyses though analysis of variance and for 

clear presentation of the data, especially when the data will be used as part of litigation. 

The main effects include factors such as species, area, time of sampling, and assessors. 

Use of the randomized, complete block design allows for 1) interactions to be calculated 

and 2) assessors to be monitored through both the main effects and sample

interactions.

Data will be collected as numbers decoded from the ballots. 

Ballot for sequential testing using 3-alternative forced-choice triangle test (see 

Appendix 3)

Ballot for use by expert assessors (see Appendix 4)

Ballot for the difference-from-control test (see Appendix 5) 

In the case of expert assessors, a pass/fail decision is recorded as Pass = 0 or 

Fail = 1 for raw odor, cooked odor, and/or cooked flavor (see Appendix 4). The 

intensity is also recorded as a value (0, 1, 2, or 3). Because the intensity scale is used

as a continuous scale in training, the numbers may be used in data analysis as well as

through descriptive statistics. 

In the difference-from-control test (see Appendix 5), data are recorded on a 

sensory scale which represents the perceived difference from the control sample. The 

difference is measured using either a 6-inch ruler with increments of 0.1 inches, or with a 

15-cm ruler with 1-mm increments. For inches, the scale is recorded from 0 (no 

difference) to 60 in. (extreme difference). For centimeters, the scale is recorded from 0 

(no difference) to 150 cm (extreme difference). In both cases, results are reported to the 

nearest whole number; no decimal fractions are recorded. 

33 
4.4 Test systems for assessor selection (both expert and trained 

assessors) 

4.4.1 Model system solution of water-soluble fraction of petroleum 

The formulation of chemicals present in the water-soluble fraction of crude oil is 

presented in Figure 4. This formulation, developed by Derek Murray, Canada 

Department of Fisheries & Oceans (Freshwater Institute, Winnipeg), was first used in 

1985. This model system has been used in selecting assessors when data are used in 

litigation. 

Hydrocarbon component Amount used

(mg/L = ppm) 

Actual amount used 

(μL/L) 

Benzene 5 5.8

Toluene 5 5.8

ethyl benzene 5 5.8 

m-xylene 5 5.8

p-xylene 5 5.8

o-xylene 5 5.8

n-propyl benzene 2 2.33 

1,3,5-trimethyl benzene 2 2.33 

cumene (isopropyl benzene) 2 2.33 

cymene (isopropyl methylbenzene) 2 2.33 

Total 38 ppm

Figure 4. Model system solution of water-soluble fraction of petroleum for testing sensory

assessors.

Serial dilutions are prepared at approximately 38, 19, 9.5, 4.75, and 2.375 ppm. 

Suggested sets for the triangle test are: 

Control: 2 samples, 9.5 ppm: 1 sample, 

Control: 2 samples, 2.375 ppm: 1 sample, 

Control: 2 samples, 4.75 ppm: 1 sample. 

These samples are presented in the 3-alternative forced-choice (AFC) formats 

of the triangle test. In this case, the sample sets always contain two control samples 

(clear) and one tainted sample. This allows the taint to be assessed against a clear

reference at all times, and makes the test more sensitive in allowing assessors to 

distinguish the presence of the petroleum tain

34 
4.4.2 Tainted and non-tainted known samples 

Laboratory-controlled known tainted ("live") and non-tainted control samples is 

the most realistic method for selecting assessors. Although this method is very costly 

and labor intensive, it will provide the most realistic conditions (Poels et al. 1988; 

Ackman et al. 1991; Davis et al. 1992) and the taint is presented in the actual seafood 

system. A detailed laboratory exposure procedure (Hufnagle 2000) is included in 

Appendix 7. 

4.4.3 Solutions of 1-butanol 

An alternative test is based on the use of solutions of 1-butanol (as described in 

ASTM E544; Appendix 1). In this case, the triangle test uses two sets of samples: one 

in which the control sample is a clear reference, and a second in which the control 

contains the test compound, to make the test more difficult. This test has been 

developed for use by York and Zhang (1998) for testing assessors of airborne malodors 

and may be used for other taint assessments as well. 

The test sets are comprised of: 

Series 1 [2 clear reference (water) plus one 80-ppm 1-butanol in water] 

3 sets each, min [2 clear reference (water) plus one 40-ppm 1-butanol in water] 

Series 2 [2 20-ppm 1-butanol in water plus one 80-ppm 1-butanol in water] 

3 sets each, min [2 10-ppm 1-butanol in water plus one 40-ppm 1-butanol in water] 

Each of these series is presented as separate, sequential testing procedures in 

which the assessor must pass the first test to proceed to the second. The assessor 

must pass both procedures to be accepted. 

(NOTE: In some cases, it is possible for a candidate to perform poorly in the 

butanol test, but to perform very well with actual petroleum-based samples). If at all

possible, model systems outlined in 4.4.1 and 4.4.2 should be chosen. 

35 
4.5 Data analysis for evaluating assessor candidates 

Data from the testing can be recorded as below, and transposed into a suitable 

format for analysis of variance through programs such as Microsoft ExcelTM. For 

analysis through SAS, a format such as shown in Appendix 8 is used. 

Species Location Date Sample # Analyst Results 

1 2 3

4.5.1 Data analysis for difference-from-control test 

1) For each sample/code/panelist, measure the response using a 15-cm ruler. 

Record the response as a measurement in millimeters (to the nearest mm.). 

The scale is therefore 0 to 150. 

2) Record the response in an electronic data table, such as in Excel, or coded 

appropriately for analysis by SAS or SPSS programming through analysis of 

variance for difference from the control sample. The control sample will show 

some readings that will give an indication of the sensory “noise” in the test

method. 

3) Use the appropriate available program to analyze the data.

4.5.2 Data analysis using SAS 

The following is an example of the format for data coding for a randomized 

complete block design for the difference from control test. Each sample, which is 

assigned a unique three-digit code, has the following information associated with it:

36 
Spill site 

Site 1, Site 2, etc., as identified in sampling plan for the area 

1 = ............................................... 

2 = ............................................... 

3 = ............................................... etc. 

Date 

Each sampling date and/or time is given a unique number code 

1 = ............................................... 

2 = ............................................... 

3 = ............................................... etc 

Species sampled 

Each species of seafood sampled 

1 = ............................................... 

2 = ............................................... 

3 = ............................................... etc 

Replication 

Number of replicate samples tested – each is coded individually 

1 = ............................................... 

2 = ............................................... 

3 = ............................................... etc 

Assessor

Unique number assigned to each assessor 

1 = (name) 

2 = (name) 

3 = (name) etc.

This is then coded into a worksheet in a program such as Excel (which can be 

imported into SAS or SPSS). 

Site Date Species Replication Assessor Sample code

(3-digit) 

Reading 

1 1 1 1 1 (aaa)

1 1 1 1 2 (aaa)

1 1 1 1 3 (aaa)

1 1 1 1 4 (aaa)

1 1 1 1 5 (aaa)

1 1 1 1 6 (aaa)

1 1 1 1 7 (aaa)

1 1 1 1 8 (aaa)

1 1 1 1 9 (aaa)

1 1 1 1 10 (aaa)

1 1 1 1 1 (bbb)

1 1 1 1 2 (bbb)

1 1 1 1 3 (bbb)

1 1 1 1 4 (bbb)

1 1 1 1 5 (bbb)

1 1 1 1 6 (bbb)

1 1 1 1 7 (bbb)

1 1 1 1 8 (bbb)

1 1 1 1 9 (bbb)

1 1 1 1 10 (bbb)

etc. etc. etc. etc. etc. etc. etc.

37 
4.5.3 Data Analysis using Microsoft Excel

Examples of data recording for analysis using the Data Analysis subroutine 

under Tools:

One-way ANOVA 

Two-way ANOVA with Replication 

Two-way ANOVA without Replication 

Only simple ANOVAs are possible with Excel. If more than two main effects are 

tested, SAS or SPSS or their equivalent must be used.

38 
5.0 

Facility Requirements for Sensory Evaluation of Seafood

5.1 Maintaining a neutral environment 

The facility in which objective sensory evaluation is conducted is an essential 

component of sensory test protocols. Sensory testing generally requires a controlled

neutral environment in which samples can be evaluated for their intrinsic attributes, here, 

the possible presence and intensity of taint from exposure to petrochemicals. The 

testing environment must not interfere with or influence the sensory test. Both ASTM 

and ISO provide excellent guidelines for facility design (see Appendix 1). 

Principle of facility-design requirements: 

A special test room or area in which to conduct sensory evaluations under constant 

controlled conditions with a minimum of distractions. 

To control the effects from introductions of physiological or psychological errors 

into human assessments, e.g., background odors causing adaptation and reduced 

sensitivity. 

Components of the neutral environment include: 

• lighting of appropriate quality and intensity for the assessments, 

• 

• 

ventilation that is appropriate and adequate to remove odors given off by the 

samples during testing, and 

freedom from distractions. 

Another important consideration is ease of sanitation and the use of products that 

do not add odors of their own into the test area (odor-free soaps, etc.) Various 

publications describe the construction of sensory facilities, including ASTM STP913 

Physical Requirement Guidelines for Sensory Evaluation Laboratories (see Appendix 

1). 

In evaluating seafood following an oil spill, consideration must be given to the 

choice of testing locations, as well as to field vs. laboratory testing. It is important to also 

consider chain of custody during the handling, preparation and evaluation of samples 

(see Section 6.1). 

39 
5.2 Sensory testing at the spill site 

Field-testing involves actually bringing the assessors to the site where samples 

are harvested for sensory evaluation. This approach has several disadvantages 

following an oil spill: 

Lack of control over ambient conditions (e.g., air temperature and humidity, 

provision of appropriate shelter). 

• 

• 

• 

Interference from and adaptation to, environmental odors (e.g., spilled oil, fuel on 

the boat or ship; rigging, nets, etc.). 

Exposure to distractions (e.g., cleanup personnel, equipment noise, media 

presence, etc.). 

When expert sensory assessors were tested in England on their ability to 

conduct quality evaluations of products in a field (market) setting, as well as in a 

laboratory, their evaluations were shown to be accurate in both settings (Aust et al. 

1985). However, because of ambient conditions at the oil-spill site that could 

compromise the objectivity of the testing—and the likelihood that the sensory data on 

seafood taint would be a component of possible legal actions—we recommend that all 

sensory assessments relative to oil spills be conducted in an appropriate laboratory 

setting where the testing environment cannot be challenged.

5.3 Sensory testing in the laboratory

An appropriately designed laboratory, preferably one specifically designed for 

sensory testing or one that can be converted as such, is the best choice. The key is 

providing adequate equipment and space for sample storage, preparation, sample 

evaluation, and data analysis. 

Another concern during sensory testing of seafood following an oil spill is the 

presence of other interested parties (such as media, industry representatives, fishers,

etc.), all with a vested interest in the results of the sensory tests. It is essential that they

not be allowed to interfere in the assessors concentration on their tasks on the sensory 

tests; i.e., they should be kept out of the sensory testing room when assessors are 

evaluating seafood samples. 

40 
5.3.1 Sample-preparation area in the laboratory

It is critical that the sample preparation area be physically separate from the 

sample evaluation area. The preparation area is used for the storage and handling of 

seafood samples and for the preparation of samples for sensory evaluation (in the test 

area). The facility should be constructed so as to comply with the requirements of good 

manufacturing practices for the design and construction of fishery facilities, and all 

equipment used in the area must also comply with the requirements for equipment used 

in fish-processing. The facility design must also be appropriate for a sensory evaluation 

laboratory, e.g., the rooms must be designed so that odors from sample preparation and 

cooking do not transfer into the sensory evaluation area. 

The sample-preparation area should provide: 

• 

• 

• 

• 

• 

• 

• 

• 

– 

– 

– 

– 

refrigerators and freezers adequate for the temporary storage of chilled and 

frozen seafood, and for the freezing of samples. Freezers must have < -20o C 

temperature capability. 

storage facility for glassware used for sample presentation for evaluation 

tables and benches (one or more) for the preliminary handling and inspection of 

batches of material, 

table (at least one) suitable for the wet-processing operation of filleting of fish, 

handling of crustaceans and molluscs, preparation of blended samples (BIFs), 

etc. 

counter-space suitable for the preparation and coding of final samples for 

serving in the evaluation area, 

large sink (at least one) for thawing samples and for washing containers, 

utensils and equipment used in the preparation and evaluation areas. 

cooking facilities (microwave ovens, steamers, etc.) for the cooking of samples 

as needed during evaluation. Stoves should be electric (gas or propane is 

another source of potential off-odors in the background air). 

equipment including: 

stainless-steel trays, medium (~50x40 cm) and large (~70x60 cm) 

filleting boards, filleting knives, sharpening stone and steel 

plastic or metal containers for fish offal 

containers for other rubbish 

41 
utensils and materials for cleaning and disinfecting premises, 

equipment, and utensils 

– 

– 

– 

– 

– 

• 

• 

• 

glass or ceramic baking dishes with lids (not plastic), suitable capacity 

for holding samples of finfish, molluscs, and crustaceans 

digital thermometer, range -50 to 300o F (-45 to 149o C) 

electronic balance 

assorted stainless steel kitchen utensils, knives, serving spoons, etc. 

If possible, all cooking equipment and utensils should be kept separate for the 

control and suspect samples. If functionally, it is not possible to keep the two groups of 

equipment separate, everything must be fully cleaned in between sample sets using 

unscented soap and several rinses in odor free water. Cooking equipment such as 

microwave ovens and steam tables must be kept separate, as it is not possible to

completely clean these in between sample sets. 

5.3.2 Sensory-evaluation (testing) area in the laboratory

This area is to be used only for sensory evaluation (testing) of raw and cooked 

seafood samples delivered from the sample-preparation area. There must be no

preparation of products in this area. The surroundings should be sensory-neutral (e.g. 

color, odor) and free from distraction, so that the personnel involved in the sensory test 

can concentrate on evaluating the products. 

This area should be constructed and furnished so that it can be maintained in a 

clean and hygienic state. However, because there should be no seafood preparation in 

the area, it need not comply with requirements for seafood-processing facilities. It 

should, however, comply with the guidelines for food preparation areas in catering 

establishments and with ASTM STP 913 (see Appendix 1). 

Floors should be finished with a seamless, waterproof coating. 

Wall surfaces should be smooth and painted white or very light, neutral grey or 

beige, using washable paint; or finished in tile or odor free plastic sheet material 

in white or neutral grey or beige. 

Workbenches should be constructed of, or finished in, impervious material that 

can be sanitized and disinfected. Any joint between benches and walls should 

be sealed with waterproof mastic. Benches may incorporate cupboards and 

42 
drawers, and cupboards may be fitted to the walls above the benches. Bench 

tops should be white or pale neutral grey or beige. 

• 

• 

• 

• 

• 

• 

– 

– 

– 

Lighting should be from fluorescent tubes providing about 1000 lux/m2 (92.9 or 

approximately 100 foot-candles), of color-matching quality (5000o K or 6000-

6500o K), and with a color-rendering index of greater than 90%.

Air handling equipment to create positive pressure to facilitate removal of odors. 

Supplementary electronic air purifiers with activated carbon filters may also be 

used. 

Room temperature should be controlled to between 68 to 75o F (20 to 24o C), 

and relative humidity is 45%, so should be within that range. 

Washbasin or sink supplied with hot and cold water and odor-free hand soap. 

Odor-free drinking water should be available for rinsing during evaluation 

sessions, either filtered water from the laboratory water supply, or bottled water 

Small equipment including 

warming plates to keep cooked samples at serving temperature 

cutlery (forks, spoons, table knives) 

glass jugs and/or beakers for water or other rinsing materials 

The sensory-evaluation area is arranged in one of two different ways, depending 

on the type of sensory evaluation being conducted and the type of assessors being used 

(expert or trained). 

5.3.3 Workshop facility

Expert assessors usually work in a workshop-type facility, where samples are 

laid out in individual stations and the assessors move from one sample to another to

perform the evaluations. This area must meet the requirements for lighting and 

ventilation (odor control), minimize distractions, and ease sanitation. 

A workshop facility consists of large areas of benches (e.g., counters or 

stainless-steel tables on casters for easy mobility) on which are movable dividers: threesided units either hinged to the wall or free-sanding. Dividers are constructed of nonporous, easily cleaned materials, as are the countertops. Individual samples are placed 

in each of the divided spaces, with assessors moving from one sample to another. If

dividers are not available, assessors may work on samples in the same area if they are 

43 
positioned far apart and are not facing one another. This type of facility is designed to 

accommodate larger sample sizes and to facilitate movement of assessors so that all

assessors can examine every sample (see Section 6.4.2). 

5.3.4 Booth facility

Trained assessors usually work in a traditional booth facility in which the 

assessors are stationary in booths and the laboratory technicians bring the samples to 

them. In this facility, individual booths are provided to control the test conditions and 

provide a comfortable evaluation environment. Smaller, individual samples or sample 

sets are presented to each assessor for evaluation, and data are collected from the test 

ballots (see Appendix 5 for ballot sample). In this type of facility, each person receives 

his or her own individual sample or set of samples. The individual samples are made 

homogenous in nature by preparing small aliquots from multiple blended organisms (see 

Section 6.1.2.2). Criteria for construction of panel booths are given in ASTM STP913

(see Appendix 1) and generally include: 

Enough booths for the size of the sensory panel (panel sessions are scheduled 

to accommodate individual assessors). 

• 

• 

• 

• 

• 

• 

• 

• 

Countertop and walls are constructed of non-porous material and are neutral in 

color and durable. 

Booths are generally 27 to 32 inches wide (~69 to 82 cm) to allow adequate 

workspace (for tray, ballot, judge), and are fitted with a hatchway door for sample 

presentation and removal. 

Booths may be computer-equipped for data acquisition during sensory testing 

Dividers extend beyond the countertop to minimize distraction during panel 

sessions. 

Lighting should be even and of the quality and quantity specified above

Booths are equipped with adjustable chairs of appropriate height and having 

casters for ease of mobility. 

Booths may be equipped with rinse sinks (although not generally recommended 

because of specialized cleaning needs and potential problems with odor control). 

44 
6.0 

Sample Handling, Preparation, and Presentation 

in the Laboratory 

6.1 Personnel involved in sample handling, preparation, and 

presentation 

Assessors who will evaluate the samples for presence of taint should not handle 

or help prepare the samples at any stage before the test. 

• 

• 

• 

• 

The individuals who will be responsible for preparing samples must be trained 

and are usually referred to as facilitators or technicians. Individuals who 

prepare the samples can not participate as assessors. These individuals should 

follow the guidelines for odor assessment panels and refrain from using any 

scented personal care products in any form (especially perfumes, after-shaves, 

etc.). These individuals must not smoke, must have clean, odor-free hands, and 

must wear clean clothing that is odor-free. Lab coats or aprons should be worn 

only in the laboratory setting. 

6.2 Secure handling of samples 

To ensure chain of custody, samples are to be handled in a secure manner at 

all times, and their inherent sensory characteristics are to be preserved (see also 

Section 3.0). 

6.2.1 Sample receiving 

Keep detailed records of the date and amount of sample received, sample 

condition, labeling and codes present, storage procedures, and names of 

personnel handling the samples (see Appendix 10 for an example of a chain of 

custody form and detailed instructions). Notes should be taken in a hardbound 

notebook specifically designated for this project. If control samples were 

collected, make sure that they are clearly labeled. 

Upon receipt, unpack samples immediately and check for any physical damage. 

Have a trained sensory assessor check to see if any quality changes have 

occurred. Samples should not be decomposed. 

45 
If sensory testing is to be done immediately and can meet the 24-hour time 

window, re-ice and refrigerate immediately (see storage procedures in Section 

6.2.3 below). 

• 

• 

• 

• 

• 

• 

• 

• 

• 

If samples are shipped frozen, check to see that an adequate frozen state was 

maintained. If any samples have thawed, separate these from the others and 

label. Have a trained inspector or expert assessor check for decomposition). 

After unpacking, record sample information and place immediately on ice or in 

frozen storage as described in Section 6.2.3 below. 

6.2.2 General principles of sample preparation 

The goal is to prepare samples for presentation to the assessors without causing 

any quality changes or imparting any off odors/flavors due to handling or cooking. 

Personnel who will be preparing the samples should perform preliminary 

sample-preparation trials to determine and standardize thawing and cooking 

times. 

If samples can be tested within 24 hours of capture, freezing is not necessary as 

long as samples are kept adequately cold (4° C or below). 

Only clean glassware, aluminum foil or stainless steel should be allowed to come 

in contact with the samples at any time. Any other materials, particularly plastic 

packaging material, could impart, or be suspected of imparting off odors and/or 

flavors. Make sure that all thaw water is clean and odor-free. 

If control samples are incorporated into the test design, these samples must be 

handled, stored, prepared, and presented in exactly the same manner as the 

suspect samples. 

If chemistry is to be performed, work with the chemists to determine the numbers 

and volume of sample that they will need. Chemistry samples are to be handled 

in exactly the same manner as sensory samples. If correlations will be 

performed on the chemistry and sensory data, measurements should be taken 

from the same sample, as fish do not taint uniformly. 

An experimental design must be determined before sample preparation begins 

(see Section 9.0). Prepare enough samples to ensure enough for each 

treatment and replication. An expected flesh recovery table is included in

Section 2.7.2. 

46 
In addition to the muscle tissue, it is common in certain societies to consume 

other parts of finfish and crustaceans such as the roe, tamale, or certain organs. 

In this case, all parts normally consumed should be evaluated for tainting. For 

pooled, blended samples, enzyme-containing organs should be separated from 

the muscle tissue and evaluated separately. 

• 

• 

• 

• 

Nothing may be added to change the odor or flavor of the edible tissue. This 

includes condiments, such as salt. 

For expert assessors, either intact tissue portions or whole organisms will be 

prepared for testing. 

For trained assessors, individual foil packet samples (BIFs) will be prepared 

from the normally consumed portions of pooled multiple organisms. 

From this point forward this section is organized according to the 2 sample 

preparation styles (“intact organisms” and “pooled, blended organisms”) as necessitated 

by assessor and test type and described above. A full description of each sample style 

can be found later in this section. 

Table 2. Summary flowchart of sample preparation and presentation. 

Intact single organism 

samples for 

expert assessors

Pooled, blended multi-organism

samples for 

trained assessors

Single organisms, or parts thereof, presented in

covered glassware

Multiple organisms, blended, portioned, and 

presented in individual foil packets. (BIFs)

One blind-coded organism presented at each

station; assessors move from station to station.

Stationary panelists are presented with multiple 

blind-coded samples at each station.

All assessors evaluate each sample. One assessor evaluates own set of foil-packet 

samples.

Vacuum-sealed samples thawed under refrigeration

or in cool, running water.

Frozen foil packets thawed under refrigeration or 

cooked from frozen state.

Raw samples presented first for odor evaluation in 

covered glassware at ambient temperature.

Samples evaluated in cooked state only. For 

odor, then flavor.

Samples microwaved in covered glassware to 

internal temperature of 160° F and placed on

warming trays back at stations in evaluation lab.

Samples steam-cooked 7 mins. if thawed, or 

10 mins. if frozen. Transfer one set for each panelist 

to warming trays in evaluation booths. 

In pre-determined order, assessors evaluate odor of 

all samples found negative for taint in the raw odor 

evaluation. Assessors then taste all samples found 

negative for taint in the raw and cooked odor

evaluation steps (see Section 7.2).

In predetermined order, assessors evaluate odor of 

all samples first, re-folding the packets as they go. 

Assessors then taste all samples found negative for 

taint by odor evaluation (see Section 7.3).

47 
6.2.2.1 Intact organism samples 

Intact organism samples are usually presented to expert assessors, and are 

presented raw first, then cooked as outlined below in Section 6.3.1. 

Finfish Remove edible muscle tissue by filleting. If the species is commonly 

sold and consumed skinless in the marketplace, remove the skin. If the species 

is usually sold skin-on, leave the skin on the fillets but remove scales first from 

the entire fish. Keep cool if testing is to be done immediately, or wrap each fillet

in heavy-duty aluminum foil, vacuum-seal and freeze at < -20o C. 

• 

• 

• 

• 

• 

• 

• 

• 

Bivalves or Mollusks Rinse live organisms in shell, organize into sample units 

of 3 to 6 (see Section 2.0), and keep cool if testing is to be done immediately. If 

samples are to be tested later, wrap 3 to 6 live, in shell organisms together in 

heavy-duty aluminum foil, vacuum-seal and freeze at < -20o C. 

Crustaceans Keep cool and moist if testing is to be done immediately. If 

testing is to be done later, place live organisms in freezer until all movement 

stops, then remove, wrap with heavy-duty aluminum foil, vacuum-seal and freeze 

at < -20o C. 

6.2.2.2 Pooled, blended samples 

Pooled, blended samples are usually presented to trained assessors. To 

prepare pooled samples, the edible parts of multiple organisms are blended, divided into 

20-gram aliquots and sealed in individual foil packets as outlined below. These samples 

are evaluated in the cooked state only. 

At least 6 organisms are recommended for pooling per sample to minimize the 

effects of natural flavor differences among organisms; however, a minimum of 

three organisms can be acceptable if samples numbers are limited or the 

individual organisms are large. 

Standard measurements, such as size, weight, length and sex (if possible), 

must be recorded before pooling. 

Detailed-harvesting records must be kept. Pooled samples must be from the 

same harvest location. 

Sample preparation should result in uniform samples. 

Keep seafood tissue cool at all times. 

48 
If preparing samples from frozen seafood, thaw samples under refrigeration only 

enough to handle. 

• 

• 

• 

• 

• 

• 

• 

Finfish Blend edible tissue from 6 fish just long enough to homogenize. 

Bivalves Remove the meats from six organisms and blend. 

Crustaceans If any organs or other body tissues are commonly eaten other 

than muscle tissue, these must also be evaluated for taint, but kept distinct and 

evaluated separately. First, separate commonly consumed sections from six 

organisms, then pool, blend, and freeze. (For example, for lobsters, pool, blend 

and prepare individual samples with the muscle tissue from six organisms, 

separately blend the tamale from six, etc.). 

6.2.3 Storing samples 

All frozen samples must be protected from dehydration and oxidation either by 

vacuum sealing or through a combination of glazing and airtight wrapping. The sample 

must be wrapped in heavy-duty aluminum foil before placement into any plastic vacuum 

bag or plastic wrapping.

Freeze samples quickly and store in a freezer at -20° F or below, keeping 

samples from different sources separate and clearly labeled. The freezer must 

be clean and odor-free. 

For security purposes, the freezer should have a lock, or samples must be 

stored in a locked container or compartment in the freezer. The number of 

personnel with access to the samples must be limited and recorded. 

The freezer should be equipped with a temperature alarm system and the 

freezer temperature should be periodically monitored. 

6.3 Sample preparation for sensory testing 

Prior to each day of sensory testing, identify and gather the samples that will be 

tested on the following day and organize by sessions. 

All sample preparation will be done in the preparation area before being brought 

to the evaluation area of the laboratory. 

49 
6.3.1 Intact single/multiple organism samples 

As stated above, this type of sample consists of whole or edible parts from single 

or multiple animals and is usually presented to expert assessors. These samples will be 

evaluated for raw odor, then cooked and evaluated for odor and flavor. Samples should 

be presented as they are normally purchased and consumed in the marketplace. This 

will vary with species and region (i.e., in the United States, finfish is usually purchased 

and prepared in the filleted state, either skinless or skin-on, depending on the species, 

while in many other countries, it is usually purchased and prepared whole or dressed). 

Raw samples should be presented at ambient temperature. These samples should be

presented to assessors as soon as possible and not allowed to remain at ambient 

temperature, as this will cause quality changes. 

Frozen samples must be thawed in their vacuum-sealed packaging, either under 

refrigeration overnight, or in cool running water before the session. Allow them to 

reach room temperature before presenting to the assessors.

• 

• 

• 

• 

Chilled (never been frozen) samples are to reach room temperature before 

testing. 

Raw samples must remain, after thawing, at refrigeration temperature and in 

their vacuum sealed packages until approximately 1 hour before the test, at 

which time they are brought up to ambient temperature in covered glassware. 

After initial raw odor evaluation by the assessors, the same samples will be 

cooked by the facilitators and placed back in the evaluation laboratory. 

Cooked samples are to be heated to an internal temperature of 160° F. 

Appropriate cooking methods include steaming or microwaving in glassware. 

Samples must be cooked uniformly, and equipment must be calibrated. Perform 

cooking trials for each species, each type of cooking vessel, and each piece of 

cooking and warming equipment. Note on each piece of equipment the specific 

cooking and/or warming instructions required bringing samples to an internal 

temperature of 160° F for each species. Samples are to be kept warm and 

maintained at a temperature of 140–150° F with electric warming trays at the 

booths or stations in the sensory evaluation laboratory. 

50 
6.3.2 Blended, pooled samples 

Blended, individual foil packets (BIFs) can be cooked either from a frozen 

state, or from a thawed state. Samples should be uniform in appearance, 

amount, and temperature. To minimize browning of the samples, steaming is 

preferred. 

• 

• 

• 

• 

• 

• 

• 

To cook, arrange foil packets on a rack in a steamer, allowing enough room for 

steam to circulate. Cook for about 7 minutes if thawed, or 10 to 12 minutes if 

frozen (a trial run should be conducted ahead to determine exact times). 

Transfer cooked samples via stainless-steel tongs to electric warming trays at the 

booths in the evaluation laboratory to maintain a temperature of 140 to 150° F. 

Do not hold samples on warming trays longer than 15 minutes. 

6.4 Sample presentation in the evaluation area

6.4.1 Preliminary preparations 

A set of 3-digit random numbers for blind-coding the samples and a template for 

randomized presentation order should be generated ahead of time. 

6.4.2 Sample placement and timing 

The sample design must include randomized order of presentation of samples 

within a session (see Section 6.5 below). 

All coded samples should be placed at booths or stations in the evaluation 

laboratory by the facilitators before the assessors enter the area. 

Samples should be presented in sessions (or sets) with a 15 to 20 minute break 

in-between. 

Assessors should generally evaluate a maximum of eight samples per session to 

minimize sensory fatigue and carry-over effects. 

For trained assessors, multiple samples (~ 8) are placed at each booth or station 

where the panelist remains stationary. With expert assessors, each intact 

organism sample is presented at a booth or station and the assessors rotate 

among them. All assessors evaluate all the samples. 

51 
For trained assessors, the order of sample presentation within a session must 

be randomized. With expert assessors, order is randomized as they rotate 

among the stations. 

• 

• 

• 

• 

Intact organism samples should be presented in glassware large enough to 

allow volatiles to equilibrate in the headspace for sniffing. The ratio should be 

about 1/3 sample to 2/3 headspace. Samples must be covered at all times to 

allow volatiles to accumulate in the headspace, except for when an assessor is 

actually engaged in smelling or tasting. 

6.4.3 Presentation of intact organism samples 

All samples are random coded in microwave-safe covered glassware (such as 

Pyrex) and placed in pre-determined positions in the evaluation area in the raw state 

first before any cooked evaluation occurs. After the assessors evaluate all the raw 

samples, the samples are removed from the evaluation area, cooked, and placed back 

at their original stations in the evaluation area on warming trays. The assessors should 

leave the evaluation area for a break during this time. 

Raw evaluation Raw samples are presented in coded, covered glassware. 

Assessors will follow the raw odor evaluation protocol as stated in Section 7.2.3. 

Cooked evaluation Facilitators will remove samples from their booths or 

stations and cook according to Section 6.3.1. Facilitators then place cooked 

samples back in their original positions in the sensory lab. Samples should 

remain in their covered glass container at all times. Samples must be placed on 

warming trays that have been set to maintain an internal sample temperature of 

145–150° F. Assessors will follow the cooked odor and flavor evaluation protocol 

for expert assessors, as stated in Section 7.2.3. 

6.4.4 Presentation of pooled, blended samples 

Facilitators place multiple, cooked and coded foil packets, in order, on a warming 

tray at each booth or station. Order of presentation is usually left to right, front to back.

Assessors will evaluate the samples following the protocol for trained assessors, as 

stated in Section 7.3. 

52 
6.5 Assigning random sample-presentation sequences 

Randomizing sequences for sample presentation should include: 

1) Random order of sample presentation among assessors at each 

session. Within the set of samples presented at one session, randomize the 

order of presentation such that no two assessors get samples in the same 

order. This is easily done with a random-number table described in 

Appendix 8. This can be done for both expert and trained sensory 

assessors. 

2) Random order of sets of samples presented to each assessor at each 

session. In selecting panels, such as when using the triangle test, the sets 

of samples are randomized for each assessor, and the sequence of samples 

within each set of three is also randomized. This requires careful attention to 

the randomization process and careful record keeping for sample 

presentation.

3) Random presentation of sets of samples over all sessions. In a larger 

study and when using trained assessors, by order of presentation over all 

sessions (when this is possible). This occurs when all of the samples have 

been prepared ahead of time (as for the BIFs), and individual sets can be 

drawn for each panelist. This is not usually possible for expert assessors, as 

all must examine the same sample within the same short time period. 

4) Exceptions There are certain exceptions to the random order of samples, 

the most important one being threshold studies which require ascending or 

descending series of concentrations. In this case, blank samples are inserted 

at the beginning and within each series, with the number of blanks varying to 

minimize predictability. 

Detailed instructions on the use of random codes and generating random 

numbers, and randomizing samples are included in Appendix 8. 

53 

7.0 

Sensory Evaluation Protocols

7.1 General sensory testing procedures

The following points are common to all of the sensory test methods described in 

this document. 

1) Do not allow participants to taste any seafood that has died or is suspect of

dying as a result of the oil spill. 

2) Before entering the evaluation room, the assessors should wash their hands 

with odorless soap and dry them with low odor (white) paper towels to 

remove any trace of residue. Assessors must wear clean, odor-free clothing 

and refrain from using any scented personal care products. Assessors may 

not smoke before or during testing. Assessors may not wear clothing that 

has been exposed to cigarette smoke, including lab coats, etc. 

3) Assessors must not smoke during the test. 

4) During testing sessions, assessors should avoid or minimize touching 

samples. They should clean hands of any sample residue between each 

sample using unscented soap or, if sinks are not available, low-odor paper 

towels dipped in odor-free water. This is to prevent cross-contamination of 

samples and physical carry-over of any stimuli. 

5) If flavor is evaluated, participants must adhere to strict rinsing procedures 

and must expectorate all samples. 

6) Rinsing between samples using neutral materials is standard practice during 

sensory evaluation sessions. The purpose of rinsing is to prevent the carryover of stimuli from one sample to the next. Odor-free water (e.g., distilled 

or filtered) is recommended along with unsalted soda crackers. When 

crackers are used, they must be followed by a water rinse to remove any 

residue from the mouth. It has been found that using odor-free water heated 

to 50o C is useful in removing flavors between samples. In ASTM D3696-95 

(which has been superceded by E-18 1096), the recommendation is still 

given to use a dilute lemon juice rinse during panel sessions. Do not use 

lemon juice rinse! Lemon juice can interfere with low levels of sourness in 

the samples. 

55 
7) Human assessors are susceptible to fatigue and adaptation to petroleum

odors/flavors that may diminish their ability to detect taint. Samples should 

be arranged in sets with maximum number in each session, and assessors 

must be given a break between sets (see Section 6.4.2). Assessors must 

also take sufficient time between samples within a session. 

8) Time-out between samples is required to avoid carry-over of odor/flavors 

from the previous sample. A minimum of 1 minute should be taken between 

samples within a session, although a longer time may be needed in specific 

testing conditions. Assessor fatigue is minimized by rinsing and by limiting 

the number of samples that are analyzed at each session. The number that 

can be tested will be established during training. Generally speaking, if 

there is a strong carry-over effect, 1 to 3 treatments with appropriate rinsing 

may be the limit for number of samples per session. If carry-over effects are 

minimal, a larger number of samples can be evaluated, with appropriate

rinsing. We have found that expert assessors generally feel that eight to 10 

per session is the maximum. 

9) Panel methodology for the analysis of taint includes the use of warm-up

samples at the beginning of each test session. This allows the sensory 

systems to re-experience the sensory attributes that will be evaluated before 

the actual testing begins. Although data may be collected on these warm-up 

samples, they are not used in the final analysis.

10) Assessors should be familiar with all instructions before the test.

The following sections are divided according to protocols for expert assessors 

(as defined in Section 3.5.2.1) and for trained assessors (as defined in Section 3.5.2.2). 

7.2 General instructions for expert assessors 

7.2.1 Before testing 

• Assessors must wear clean, odor-free clothing.

• 

• 

No extraneous scents are allowed, e.g., perfume, after-shave, or breath mints. 

Assessors should not eat or drink 1/2 hour before sensory testing. 

56 
Assessors should avoid highly spiced foods the day before and the day of the 

test. 

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

Assessors may not smoke before or during the test, or wear clothing smelling of 

cigarette smoke. 

Assessors must wash their hands with unscented cleanser and odor-free water 

when they enter lab. 

Assessors must cleanse their mouth by rinsing either with odor-free water or by 

chewing an unsalted cracker, then rinsing several times with odor-free water. 

The facilitator must review the ballot and test procedure with the assessors. 

Assessors should evaluate a few warm-up samples at the start of each day of 

testing. 

7.2.2 During testing

Assessors must avoid hand contact with samples by using a knife, fork, or tongs 

to manipulate the sample. 

Assessors should wash hands with unscented soap between samples. 

To sniff or taste the sample, assessors should slide the glass covers off just a 

slight distance, then quickly slide the cover back. This retains as many volatiles 

as possible within the glassware for other assessors. 

Assessors should wait at least 1 minute between each sample within a set, 

taking longer if necessary. 

Assessors should wait at least 15 minutes between sample sets. 

Assessors should evaluate a maximum of 8 to 10 samples within a set. 

For odor evaluation, assessors should take two or three short shallow sniffs 

(sometimes called “bunny” sniffs) and standardize the distance from their nose to 

the samples. 

Assessors should cleanse their nose between samples by sniffing the back of the 

hand or arm, or the headspace over a glass of odor-free water. 

For flavor evaluation, assessors must cleanse their mouth between each sample 

by chewing an unsalted cracker and rinsing with odor-free water. Assessors 

should standardize the amount of sample placed in the mouth. All samples 

must be expectorated!

57 
7.2.3 Evaluation criteria 

The following 3-tiered procedure is recommended to minimize sensory fatigue 

and carry-over effects (see Figure 5). 

1) Evaluate the odor of the RAW sample for the presence of taint. If taint is 

detected: STOP—Sample fails. If taint is not detected, proceed to Step 2.

2) Evaluate the odor of the COOKED sample for the presence of taint. If taint is

detected: STOP—Sample fails. If taint is not detected, proceed to Step 3. 

3) Taste the COOKED sample for the presence of taint. If taint is detected:

STOP—Sample fails. If taint is not detected: Sample passes. 

Using this the 3-tier evaluation procedure described above, assessors must 

evaluate the raw odor of all the samples presented in the set first, then proceed to 

evaluate the cooked odor of all the samples found negative for taint by raw odor, then 

proceed to evaluate the flavor of all the cooked samples that were found negative for 

taint by raw and cooked odor. The principle behind this procedure is: if taint is detected 

in the raw odor of a sample, concentrations are usually well above threshold. If the 

same sample were cooked and evaluated, the perceived intensity would only be more 

intense and the assessor would be exposed to relatively high concentrations (of taint) 

that would add to fatigue and carry-over. The same is true for cooked odor vs. cooked 

flavor; if the assessor perceives taint in the cooked odor, it would only become more

pronounced in the flavor. Rinsing taint from the mouth is more difficult. 

7.2.4 Evaluation ballots 

Expert assessors who have had some descriptive training should use ballots that 

allow for recording both quantitative and qualitative information. Ballots of this 

nature usually incorporate a type of category scale with an area to record

descriptors. An example is illustrated in Appendix 4. 

• 

• Because expert assessors are intimately familiar with the seafood products they 

are assessing (see Section 8.1.1), they can disregard “normal” sensory 

attributes and focus on contamination. Expert assessors should use the ballot to 

record only the presence and intensity of petroleum contamination and to 

provide descriptors of that contamination. 

58 
Oil Spill Event 

Collect suspect and control samples (if possible)

Prepare samples, ship to laboratory 

Freeze samples if longer than 24 hours to testing 

Assemble the Expert Assessment Group at proper facility 

Preliminary validation using known samples, reference 

standards, laboratory-exposed samples 

Evaluation of suspect samples for presence and intensity of 

taint using sequence: 

Raw odor – Cooked Odor – Cooked Flavor 

Raw odor 

Yes 

Stop testing-Taint present 

No

Continue testing 

Cooked odor 

Yes 

Stop testing - Taint present 

No

Continue Testing 

Cooked Flavor 

Yes 

Stop testing - Taint present 

No

Stop Testing

No taint present – samples 

pass 

Figure 5. Sensory decision tree for use by expert assessors in evaluating petroleum taint. 

7.3 General instructions for trained assessors 

** Assessors should be familiar with these instructions before the test. 

A panel of trained assessors will evaluate 20-g packets of pooled and blended 

seafood samples. The panelists’ instructions for handling blended sample packets

during evaluation sessions include: 

• Open packets by tearing off one folded end and down one side of the foil. 

59 
• Evaluate the odor of the samples first, then close the packet temporarily. 

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

• 

If no petroleum contamination is detected, or if it is of such a slight intensity as to 

be questionable, samples must be tasted. 

To taste, divide the sample in half and do the assessment. Use second half as 

needed for re-tasting. 

Cleanse mouth after each sample set. 

7.3.1 Before testing 

Panelists must wear clean, odor-free clothing. 

No extraneous odors or scents should interfere, such as perfume, after-shave, or 

breath mints. 

No eating or drinking 1/2 hour before sensory testing. 

Panelists should avoid highly spiced foods the day before and the day of the test. 

No smoking is allowed or during the test. 

Panelists must wash hands with unscented cleanser and odor-free water when 

entering the lab. 

Facilitator must review the ballot and the test procedure with the panelists. 

Panelists should evaluate a few warm-up samples. 

7.3.2 During testing 

All samples will be evaluated for odor before tasting any samples. 

Packets are re-folded after odor evaluation to retain volatiles.

Hand contact with samples must be avoided or kept to a minimum. 

If contact with sample is made, hands should be washed with unscented soap 

and/or rinsed with odor-free water before the next sample. 

Panelists should wait at least 1 minute between samples within a set, or longer if 

felt necessary. 

Panelists should wait at least 15 minutes between sample sets. 

Panelists should evaluate a maximum of eight samples within a set to minimize 

fatigue and carry-over effects. 

For odor evaluation, panelists should take two or three short shallow sniffs 

(sometimes called “bunny” sniffs) and should standardize the distance from their 

60 
nose to the sample and standardize the number and duration of sniffs. Each foil 

packet must be folded back up to retain aromatics for the tasting phase. 

Assessors should cleanse their noses between samples by sniffing the back of 

the hand or the headspace over a cup of odor-free water. 

• 

• For flavor evaluation, assessors must begin by cleansing their mouth by chewing 

an unsalted cracker and rinsing with odor-free water, repeating this procedure 

between each sample. The amount of sample placed in the mouth should be 

standardized. All samples must be expectorated!

7.3.3 Evaluation criteria 

Trained assessors do not make decisions on samples (see Figure 6). Rather, 

they evaluate samples for the degree of difference from the control sample as outlined in 

Section 8.4.2. The data are then statistically analyzed to determine whether there is a 

significant difference (see Section 8.5.2). 

7.3.4 Evaluation Ballots 

Several types of discrimination, or difference, tests may be conducted with a 

panel of trained assessors (see Section 3.3.4), although the “difference-from-control” 

test has been shown to be effective in seafood tainting situations (EEM 1996). Ballots 

will vary according to the type of discrimination test chosen. Ballots for a differencefrom-control test are illustrated in Appendix 5. 

61 
Oil spill occurs 

Trained Panel chosen for assessors (already trained) 

Collect suspect and reference samples – You MUST have reference samples! 

Prepare samples and ship to laboratory. At laboratory, prepare blended, 

pooled packets according to protocol. Freeze samples if longer than 24 hours 

to testing. 

Validation Tests using Sequential Testing to confirm ability of assessor for 

participation

Perform testing in an appropriate facility 

Cook pooled, blended sample packets and 

present according to protocol 

Results of cooked odor 

Positive 

May taste samples 

Results of cooked odor 

Negative 

Taste samples 

Results of cooked 

flavor - Positive 

Results of cooked 

flavor - Negative 

Results of cooked 

flavor - Positive 

Results of cooked 

flavor - Negative 

Data Collection using Difference from Control Test to measure the presence 

and degree/intensity of taint present (cooked odor and flavor) and to 

determine the relationship of exposed samples to control samples. 

Facilitators analyze data to determine if samples pass or fail statistically. 

Figure 6. Sensory decision tree for use by trained assessors in evaluating petroleum taint in 

seafood. 

62 
8.0 

Collection and Analysis of Test Data and Decision Criteria

8.1 Introduction 

• 

• 

– 

– 

– 

– 

– 

– 

– 

• 

• 

Because seafood sensory testing for the presence of taint requires an analytically 

based objective response, sensory assessment must be based on this type of 

evaluation. As explained in Ssection 3.2, it is important to evaluate samples 

suspected of petroleum contamination objectively and not subjectively

(according to likes or dislikes). If done correctly, objective sensory testing will 

measure the presence and intensity of a tainting substance with no allowance for 

like/dislike responses. 

If the decision is made to perform sensory testing after an oil spill, an overall 

experimental plan should be developed (see Sections 2.0 and 3.0), including the 

experimental design for collection and analysis of data. In planning the design, 

careful consideration must be given to the 

type of assessors 

type and number of samples 

size of the experiment 

number of replications 

availability of reference samples 

data collection method 

subsequent statistical analysis 

The presence or absence of control samples is pivotal to the design and datacollection method chosen. Whenever possible, blind control samples should

be included in the experiment to monitor the performance of expert assessors 

and must be included with trained panelists (see explanation below). Control 

samples must be collected immediately after the spill and handled according to 

procedures in Section 2.2. Control samples should be harvested from an 

unaffected area adjacent to the spill site. 

Each spill situation is unique! Although the examples given below have 

proven effective in petroleum-tainting situations, this document is not meant to 

imply that other types of data would be ineffective. We strongly recommend that 

63 
a statistician be consulted. See Section 9.0 for sources of more in-depth

information. 

8.1.1 Expert assessors 

Expert assessors, as described in Sections 3.5 and 3.6, are intimately familiar 

with “normal” sensory characteristics of seafood and any byproduct of deterioration in 

quality due to aging in storage, decomposition of fats, proteins, or other microbial 

contamination normally found in fish. Because of this familiarity, the expert assessor is 

able to examine samples for taint only and disregard other sensory characteristics. 

Whenever possible, control samples should be incorporated into the 

experimental design, but if they are not available, expert assessors can still 

perform the sensory testing. If control samples are not available, the expert 

assessor is able to detect taint comparing the samples to their internal “control” 

based on his past experiences and training sessions with that species (i.e., they 

know what “normal” is) (ISO 8586 –2). 

• 

• 

• 

Generally with expert assessors, both qualitative (presence) and quantitative

(intensity) information can be obtained because they have had some descriptive 

training. To obtain valid qualitative information (the identification of particular 

odor/flavor attributes), the assessor must have had some descriptive analysis 

training (ASTM MNL 13; ISO 8586; Rainey 1986). A suggested list of descriptors 

and training references relating to petroleum tainting can be found in Appendix 

2. Seafood inspectors trained and selected for their ability to detect taint—but 

with no additional descriptive training—can also be used. In this case, assessors 

would use a pass/fail system by passing a sample if no taint is detected, or failing 

a sample it taint is detected. 

8.1.2 Trained assessors 

Trained assessors (see Sections 3.5 and 3.6) are used to conduct objective 

quantitative sensory testing (i.e., to test statistically for a difference between exposed 

and non-exposed (control) seafood). With trained panels, it is always necessary to have 

control samples. 

Because this type of assessor is usually not familiar with every normal

characteristic of seafood samples, including deterioration, the difference-from64 
control test will be less problematic than the other tests (see EEM document for 

details) which have been reported (e.g. triangle (3-AFC), paired comparison, 

duo-trio). 

Trained assessors are asked to rate the degree of difference from the control, 

and are provided a scale for this purpose. 

• 

8.2 Test data types and numbers of assessors needed 

8.2.1 Data types

Data are collected to measure a sensory response, in this case, the presence of 

petroleum taint. Sensory data are generally considered to fall under one of the four 

following categories. The categories marked with an asterisk (*) are most appropriate

for measuring taint. 

Nominal* Qualitative;; in name only (i.e., yes/no, pass/fail, accept/reject). 

Assigning descriptors (without absolute relative intensity) also falls into this 

category. 

Ordinal Relative value by ranking, but with unknown relative intervals 

between categories. 

Interval* Quantitative values that increase with constant intervals. 

Ratio Quantitative values that increase by orders of magnitude above the 

previous value. 

8.2.2 Number of expert assessors needed 

Because selected expert assessors are the most highly trained (see Section 

3.5), fewer numbers of judgments on each sample are needed to draw confident 

conclusions on sample tainting. Because of the high rate of reliability, as few as 3 to 5 

assessors can be utilized. 

8.2.3 Number of trained assessors needed 

It is recommended that 10 to 15 panelists participate in the testing to ensure 

that conclusions can be drawn with confidence (Meilgaard et al. 1999). 

65 
8.3 Design and content of evaluation ballots 

Ballots are used to record the presence or absence of taint in a sample. Ballot 

design is fundamental to effective and accurate sensory analysis. Ballots incorporating 

sensory scales and terms that solicit accurate descriptions of the samples and possible 

degrees of taint are essential. 

An effective ballot must:

1) Provide a standardized format and terminology.

2) Provide a meaningful permanent record. 

3) Generate data so that a difference in the score reflects a reproducible 

variation in the factors being scored (intensity of the tainting substance).

4) Reflect general agreement on intensity of the tainting substance among 

assessors, thus minimising the scoring range used and variability among 

assessors. 

An effective ballot should: 

1) Lend itself to wide use by trained assessors. 

2) Lend itself to statistical analysis 

3) Generate improved assessment procedures and habits 

Examples of ballots, and assessor instructions for each type, can be found in 

Appendices 3-5.

8.3.1 Ballots for expert assessors 

With expert assessors, ballots can incorporate from two categories (pass/fail) to 

more categories (e.g., none, slight, moderate, and strong) that generate information that 

is more detailed. In addition, if the assessors have been trained in descriptive analysis, 

the ballots can include a space for recording descriptors (see example in Appendix 4). 

Additional information, such as intensity and characteristics of the taint, may help 

decision-makers in monitoring levels and characteristics of seafood contamination and 

demonstrate trends in the progress of the development and cleanup of the oil spill. 

66 
8.3.2 Ballots for trained assessors 

Panelists are asked to rate the degree of difference between a test and a control 

sample on a given scale (see example in Appendix 5). This produces data on the 

intensity of tainting, which is analyzed statistically for the presence of taint. 

8.4 Test data analysis 

This section describes the analysis of data from spill site samples and control 

samples included for monitoring panel performance. 

8.4.1 Expert assessors 

Expert assessors employed as seafood inspectors are accustomed to performing 

pass/fail tests using a product standard for comparison. The presence of any taint, no 

matter how slight, usually causes a sample to fail. As with any sensory test, blind control 

samples, if available, should be included to monitor the effectiveness of the experiment 

and the performance of the assessors. 

Two types of statistical analyses may be applied to expert assessors: 

1) Pass/Fail decisions may be analyzed using: 

a. Sampling tables for fish inspection, including the number of defective 

units required for the lot to fail. In this case, the tables associated with reinspection would be used. 

b. Statistical test such as the Fishers Exact Test (see Appendix 11). 

Generally, data from each assessor for each sample are examined for the 

number of hits (number of samples failed because of positive response to taint). 

Because multiple assessors evaluate each sample (see Section 6.0), a 

threshold must be established by the stakeholders as to what percentage of 

assessors must get a hit for that individual sample to fail (i.e., 3/5 or 60%, 4/5 or 

80%, 5/5 or 100%). A realistic situation might be that 4 to 5 positive responses 

for taint cause the sample to fail, 2 to 3 positive responses initiate further testing 

of samples from that particular area, 0 to 1 positive response causes the sample 

to pass. If the assessors are truly experts, there usually is much agreement and 

little variation among the data. 

• 

67 
To illustrate this, a table of data from a NOAA/FDA training workshop for 

selecting expert assessors can be found in Appendix 9. Assessors’ 

performance can also be monitored through control samples. Data can be 

quickly entered into a database programmed to automatically place samples into 

pass, fail, or continue testing categories. 

• 

2) Statistical analysis of the difference from control test using analysis of 

variance. This allows the evaluation of the presence of differences and the 

calculation of the probability levels associated with these differences. 

Decisions can be made according to predetermined probability levels (usually 

α = 0.05). 

8.4.2 Trained assessors 

The difference-from-control test is often used in quality-control situations to 

measure a difference. The nature of the difference is easier to define (i.e., taint) than in 

triangle tests, and the panelists are less influenced by other factors in the sample. The 

data gathered can be analyzed through standard statistical tests to give measurements 

of taint relative to the control samples. The test is described in detail in Meilgaard et al. 

(1999) and Munoz et al. (1992). 

For an internal blind control, some of the test samples should be the same as the 

control. The resulting mean difference-from-control of the test samples should be 

evaluated against the difference-from-control obtained with the blind controls. This 

measures the placebo effect (Meilgaard et al. 1999). 

Review and summary of the sequence of data analysis that is used for each of 

the steps in the test is: 

1) Expert Assessors 

a) Assessor selection – using sequential testing (see Appendix 6) or 

Fisher’s Exact Test (see Appendix 11). 

b) Sample evaluation as pass/fail decisions as well as measurements of 

intensity and identity of off-flavors and odors. Blind coded controls 

included to monitor assessor performance. 

68 
c) If data is collected on off-flavor intensity, it may be analyzed using the 

same procedures as for the difference-from-control test. 

2) Trained Assessors 

a) Assessor selection using sequential testing as described in Section 

4.0. 

b) Sample evaluation using the difference-from-control method and 

including blind coded samples to monitor panel performance. 

8.5 Decision criteria 

8.5.1 Expert assessors 

After pass/fail decisions are made on each sample, the pass/fails from each 

harvest location are tallied. If very few samples (1 or 2) from a particular area test as 

tainted, some tainted seafood may end up in the marketplace if harvested from that area 

and sold. It is the responsibility of public health officials and/or seafood processors to

decide what level of risk, if any, is acceptable. 

8.5.2 Trained assessors 

Generally, 25 to 50 presentations of each of the samples and the control are 

needed to determine the degree of difference (Meilgaard et al. 1999), i.e. 10 to 15 

assessors and 3 replications of the test. 

After the mean difference-from-control for each sample (and for blind controls) 

are calculated, results are evaluated by analysis of variance (or by paired t-test if only 

one sample is compared with the control). See Bibliography for more information on 

possible analytical methods. 

69 

9.0 

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75 

APPENDIX 1 

Normative References - Existing Guidelines, Standard Practices, 

And Sampling Plans for Sensory Testing 

American Society of Testing & Materials (ASTM) Standards 

Standard practice for evaluating an effluent for flavor impairment to fish flesh. ASTM D3696-89. 

Standard practices for evaluating effects of contaminants on odor and taste of exposed fish. 

Committee E-18 on Sensory Evaluation of Materials and Products. ASTM E1810-96. 

[Supersedes the sensory evaluation procedures in D3696-95, Standard practices for evaluating 

an effluent for flavor impairment of fish flesh, in Standardization News, Jan. 1997, p. 4.] 

Terminology relating to sensory evaluation of materials and products. ASTM E253-98a. 

Standard practices for referencing supra-threshold odor intensity [re-approved 1993]. ASTM 

E544-75. 

Standard test method for sensory analysis – triangle test. ASTM E1885-97. 

Manual on descriptive analysis testing for sensory evaluation. ASTM MNL 13. 1992. 

Manual on sensory testing methods. ASTM STP 434. 1999. 

Establishing conditions for sensory evaluation of foods and beverages. ASTM STP 480-84. 

Guidelines for the selection and training of sensory panel members. ASTM STP 758. 1981. 

Physical requirement guidelines for sensory evaluation laboratories. ASTM STP 913. 

Canadian Government Standards

Technical guidance document for pulp and paper environment effects monitoring. Environment 

Canada EEM/1997/7 October 1997. 

International Organization for Standardization (ISO) 

Sensory analysis – General guidance for the selection, training and monitoring of assessors – 

Part I: Selected assessors. ISO 8586-1. 1993. 

Sensory analysis – General guidance for the selection, training and monitoring of assessors – 

Part 2: Experts. ISO 8586-2. 1993. 

Sensory analysis – Vocabulary. ISO 5492. 1992. 

Sensory analysis – Methodology – General guidance. ISO 6658. 1985. 

Sensory analysis – General guidance for the design of test rooms. ISO 8589. 1998. 

77 
Sensory analysis – Methodology – Triangular test. ISO 4120. 1983 

United Nations/World Health Organization (UN/WHO) 

UN/WHO Codex Alimentarius Commission. Draft guideline for the sensory evaluation of fish 

and shellfish in laboratories. ALINORM 99/18. 

UN/WHO Codex Alimentarius Commission. Procedural Manual F/3026.

Sampling Plans for Sensory Testing of Seafood

American National Standards Institute (ANSI)/American Society for Quality Control 

(ASQC). Sampling procedures and tables for inspection by attributes. ANSI/ASQC Z1.4. 1993.

International Organization for Standardization (ISO). 

Sampling procedures for inspection by attributes. ISO 2859. 

Part 1: Sampling plans indexed by acceptance quality level (AQL) for lot-by-lot

inspection. 

Part 2: Sampling plans indexed by limiting quality (LQ) for isolated lot inspection. 

UN/WHO Codex Alimentarius Commission. Procedural Manual F/3026. 

U.S. Code of Federal Regulations. Title 50, Sect. 260.57, "Sampling." 1994 (example of an 

AQL sampling plan). 

78 
APPENDIX 2 

Definitions, Terminology, and References used 

in Sensory Training for Petroleum Taint

Specific Seafood Terminology 

Associated with fresh seafood, not subject to deterioration 

Odor: Ocean air, clean seaweed, briny, slightly sweet, metallic, cucumber, melon, grassy, neutral.

Flavor: Slightly sweet, oceany, meaty/brothy, briny, fresh oil, buttery, neutral. 

Associated with seafood deterioration (spoilage) 

Odor: Fishy, oxidized, rancid, sour, fermented, yeasty, fruity, sulfury vegetable, pungent, putrid, 

fecal, cheesy, ammonia, painty. 

Flavor: Fishy, oxidized, rancid, painty, sour, bitter, yeasty, fermented, sulfury vegetable, putrid, 

fecal. 

Associated with petrochemical tainting of seafood

Odor: Petroleum, diesel, kerosene, hydraulic fluid, lube oil, dirty sour (old oil), solventy, 

chemical, pungent, acrid, burnt, creosote, tar, piney/resinous, rubbery, phenolic, nosesting. 

Flavor: Pungent, kerosene, petroleum fuel, chemical, dirty sour, warming mouth-feel, oily/waxy 

mouth-coating. 

General Sensory Definitions 

acrid/burnt Burning, irritating, pungent, aromatic; often associated with burnt wood

or smoke. 

adaptation Decreased in sensitivity to a given stimulus resulting from exposure to 

that stimulus.

ammonia Aromatic characteristic of unscented ammonia. 

anosmic Lack of sensitivity to odor stimuli. 

appearance All the visible characteristics of a substance/sample. 

assessor Any person taking part in a sensory test. 

79 
astringent The chemical "feeling" factor on the tongue or other skin surfaces of the 

oral cavity, described as puckering/dry and associated with tannins or 

alum. 

bakelite Burnt, phenolic, aromatic; reminiscent of a burnt circuit board or burnt 

plastic. 

bitter One of the four basic tastes (w/sour, sweet, salty) primarily perceived at 

the back of the tongue; common to caffeine and quinine. 

briny Aromatic associated with the smell of clean seaweed and ocean air. 

brothy Aromatic associated with boiled meat. 

burnt Aromatic associated with heated, scorched, or blackened substances. 

burnt plastic Aromatic associated with burnt plastic, such as Bakelite. 

burnt rubber Aromatic associated with higher sulfur mercaptans. 

cardboardy Aromatic associated with slightly oxidized fats, reminiscent of wet 

cardboard packaging. 

carry-over A decrease in sensitivity to a given stimulus resulting from exposure to 

previous samples containing the same stimulus.

cheesy Sour aromatic associated with aged cheese and butyric acid. 

chemical A general term associated with many types of aromatic compounds such 

as solvents, cleaning compounds, and hydrocarbons.

creosote Heavy, tar-like, acrid aromatic associated with creosote, smoke, and 

some solvents.

cucumber Aromatic associated with fresh cucumber; similar aromas can be 

associated with certain species of very fresh, raw fish.

decompose Break down into component parts; fish having an offensive or

objectionable odor, flavor, color, texture, or substance associated with 

spoilage. 

diesel Chemical-like aromatic associated with diesel fuel. 

dirty Soiled, sour aromatic. 

distinct Capable of being readily perceived. 

earthy Aromatic characteristic of wet foliage, damp soil, or slightly undercooked 

boiled potato. 

error Difference between the observed value and the true value.

error/psychological Errors that can introduce bias into sensory assessment. 

error/physiological Systemic errors that may be positive or negative. These differ from the 

statistical phenomena of random error, which are unpredictable errors 

that are random deviations of observed values from true values and that 

average to 0. 

80 
fatigue See Adaptation.

fecal Unpleasant aromatic associated with complex protein decomposition. 

feel A chemical sensation in the nose or mouth, such as astringent, cooling, 

pungent.

fermented Sour aromatic associated with rotting fruit or vegetables. 

fishy Aromatic associated with old, lower-quality fish, as demonstrated by the 

odor of tri-methylamine (TMA) or cod liver oil. 

flavor Perceived attributes of a food substance when placed in the mouth 

resulting from the stimulation of taste, odor, and feeling factors. 

freshness Concept relating to time, process, or characteristics of seafood as 

defined by a buyer, processor, user, or regulatory agency. 

fruity Aromatic associated with slightly fermented fruit. In seafood, fruity odors 

generally result from high-temperature spoilage. 

fuel oil General term to describe the aromatics of fuel oils such as diesel or

kerosene. 

gasoline Aromatic associated with gasoline. 

grassy Green, slightly-sweet aromatic associated with cut grass or very fresh, 

high-quality finfish. 

hydrocarbon Aromatic associated with fuel-combustion products. 

intensity Perceived magnitude of a sensation. 

iridescent Array of rainbow-like colors, similar to an opal or oil sheen on water.

kerosene Aromatic associated with kerosene. 

lube oil Heavy, greasy aromatic associated with lube/motor oil. 

masking Phenomenon in which one sensory attribute obscures or diminishes one 

or several other attributes present. 

mercaptan Aromatic associated with sulfur compounds, reminiscent of skunk and 

rubber. 

metallic Aroma and/or taste associated with ferrous sulfate or tin cans. 

moldy Aromatic-associated mold growth; for example, an old, damp basement. 

mouth-coating Sensation of a film coating the inside of the mouth. 

mouth-filling Sensation of fullness dispersing throughout the mouth. 

musty Aromatic associated with a moldy, dank cellar. 

noseburn Chemical "feeling" factor described as a warmth or burning sensation in 

the nasal passages when a product is sniffed. 

odor Sensation caused by stimulation of the olfactory receptors in the nasal 

cavity by volatile material. 

81 
off-odor General, non-specific term relating to characteristics that are 

inappropriate in a food system, usually related to aging or contamination. 

oxidized Aromatic associated with rancid, stale, painty, or cardboardy. 

persistent Existing without significant change; not fleeting. 

petroleum Aromatic associated with any material of petrochemical hydrocarbon 

nature. 

phenolic Harsh, irritating, medicinal aromatic associated with phenol or plastic 

Band-Aids. 

pine-like Resinous pine-tree type aromatic; may be slightly medicinal or 

disinfectant-like. 

pungent Irritating, sharp, or piercing sensation. 

putrid Aroma associated with decayed meat, usually resulting from anaerobic 

decomposition. 

quality Degree of excellence. A collection of product characteristics that confers 

its ability to satisfy stated or implied needs. 

rancid Odor or flavor associated with rancid oil. Gives a mouth-coating 

sensation and/or a bitterness perceived on the back of the tongue. 

Sometimes described as painty. 

reference Either a sample designated as the one to which others are compared, or 

another type of material used to illustrate a characteristic or attribute. 

resinous Medicinal, woody aromatic.

rubbery Sulfurous, phenolic aromatic associated with rubber products. 

salty Taste on the tongue associated with salt, sodium chloride, or odor of

brine. 

sensory Relating to the use of the sense organs. 

solventy Odor and/or nose "feel" or flavor associated with solvents such as 

acetone. 

sour Odor and/or taste sensation, generally due to the presence of organic 

acids. 

stale Odor or flavor associated with wet cardboard or frozen storage. 

sulfury Odor or flavor associated with sulfur-based materials such as matches, 

old garlic, onions, rotten eggs, mercaptans, or rubber.

sweet One of the four basic tastes on the tongue(w/bitter, sour, salty) 

stimulated by sugars. Also a sweet odor, such as vanilla extract.

82 
tar-like Aromatic associated with the heavier, tar-like substances of petroleum 

chemicals, as demonstrated by hot asphalt.

taste One of the basic senses, the receptors for which are located in the 

mouth and activated by compounds in solution. 

terminology Terms used to describe the sensory attributes of a product. 

umami Taste produced by substances such as monosodium glutamate (MSG) in 

solution. A meaty, savory, or mouth-filling sensation. 

vegetable Odor associated with sulfur-containing vegetables such as cooked

broccoli, cabbage, or cauliflower. 

watermelon Aroma characteristic of fresh-cut watermelon rind. Similar odors 

sometimes found in certain species of very fresh, raw fish. 

yeasty Aroma associated with yeast and fermented products such as bread or 

beer.

83 
Petroleum Taint References for Assessor Training 

As explained in more detail in Section 4.0, it is very important to include actual 

petroleum-contaminated seafood samples when selecting, testing, and training sensory 

assessors, whether expert or novice. Actual samples can serve as both controls and 

references (see Section 4.0). In addition, the substances listed below can serve as 

referents for developing and refining sensory terminology during the assessor training

process. 

Term Referent 

astringent (oral) alum solution 

burnt/acrid burnt toast, scorched oil 

burnt plastic burnt plastic 

cooling (nasal) menthol, etc. 

creosote creosote 

diesel diesel fuel 

earthy beets, potatoes, potting soil 

gasoline/kerosene gasoline/kerosene 

hydraulic fluid hydraulic fluid 

lube oil WD-40 

petroleum petroleum jelly 

phenolic phenol, Band-Aids 

piney pine needles, Pine Sol 

pungent (nasal) vinegar, burnt substances 

rubber rubber bands 

soapy lauric acid 

solventy acetone 

sour old oil, vinegar, yogurt, etc. 

sulfur rubber, matches, old garlic/onions, mercaptans 

tar-like tar

84 
APPENDIX 3

Expert Assessor Ballot for Recording Sensory Evaluations of 

Seafood: 3-Alternative Forced-Choice (AFC) Triangle Test 

Name

Date

Product

Sensory panel 

screening 

Six sets of three samples each are laid out in the room. Two of the three samples smell the same. 

Using this ballot, evaluate each sample set and identify the one sample that differs from the other 

two. 

Open and evaluate the samples as shown, taking two or three shallow sniffs. Evaluate the odor in 

each sample for the presence of taint. 

Within each set, evaluate the samples in the order given below. You may evaluate a sample more 

than once, if needed. Partially close the sample, as shown, when not testing it. 

Open each sample only briefly to prevent any release of odor into the test room. If you cannot 

detect any difference among the samples, you must guess. 

Sample sets 

Sample # Sample # Sample # The one sample that is different.

435 394 391 

2 433 450 717 

3 183 462 245 

4 843 700 906 

5 591 845 056 

6 130 801 295 

Comments:

1 

85 
APPENDIX 4 

Expert Assessor Ballot for Recording Quantitative/Qualitative Sensory 

Evaluation of Seafood. 

 Name:___________________________________

 Date:____________________________________

 Species: _________________________________

Open and evaluate the samples as shown. Evaluate each sample for presence of "off" odor or flavor. 

Make a Pass/Fail decision, rate the intensity (using the numerical scale), and characterize (using descriptors).

RO = Raw odor 

CO = Cooked odor

CF = Cooked flavor 

 Decision Intensity Comments/Descriptors 

scale 

Pass Fail None Strong

051 RO 0 1 2 3

051 CO 0 1 2 3

051 CF 0 1 2 3

Pass Fail None Strong 

333 RO 0 1 2 3

333 CO 0 1 2 3

333 CF 0 1 2 3

Pass Fail None Strong

758 RO 0 1 2 3

758 CO 0 1 2 3

758 CF 0 1 2 3

Pass Fail None Strong

420 RO 0 1 2 3

420 CO 0 1 2 3

420 CF 0 1 2 3

86 
APPENDIX 5

Trained Assessor Ballot for Recording Sensory 

Difference-from-Control Evaluations of Seafood. 

Name: Date:

Species: 

 

Test or Set #: 

Attribute assessed = Presence of Taint in Cooked Odor or Cooked Flavor

Do not swallow samples: EXPECTORATE any sample that is tasted. 

Follow strict rinsing procedures. 

Instructions:

1. Smell and taste the sample marked “Control” first. 

2. Smell the sample marked with the 3-digit code; if no taint is detected, or if it so slight as to be 

questionable, taste the sample. 

3. Assess the overall sensory difference between the two samples, using the scale below. 

4. Mark the scale to indicate the degree of overall difference by placing a vertical mark across the 

horizontal line at the point corresponding to the degree to which the sample deviates from the 

reference (indicated by R). 

Code No. Sensory Scale 

same as R extremely

different 

from R

same as R extremely

different 

from R

same as R extremely

different 

from R

same as R extremely

different 

from R

same as R extremely

different 

from R

same as R extremely

different 

from R

87 

APPENDIX 6

Control graph for sequential analysis using the triangle test method for assessor selection. 

 Graph for Sequential Analysis for Selection Panel Trainees

Using Triangle Tests

-2-4

86420

16141210

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

n, number of triangle tests, (cumulative)

)ev ati ul umc s ( st te ectrro c of ber num n,

Accept

Continue Testing

Reject

alpha = 0.05

beta = 0.05

po = 0.45p1 = 0.70
90 
APPENDIX 7

Method for Exposing Live Seafood to Petroleum Products for 

Selecting and Training Sensory Assessors. 

Memorandum Report (February 2000) 

Larry Hufnagle 

Environmental Conservation Division

Northwest Fisheries Science Center 

National Marine Fisheries Service, NOAA 

Seattle, Washington 98112

Three commercially important seafood species were exposed to 25-ppm diesel 

or Monterey Crude oil to produce sensory-analysis training materials for the National 

Marine Fisheries Service's (NMFS) Sensory Branch Inspection Services and the U.S. 

Food and Drug Administration. The exposure was conducted at the Mukilteo Field 

Station of the Northwest Fisheries Science Center in Mukilteo, Washington. Three 

classes of experimental organisms were chosen for the experiment—a bivalve (oyster), 

crustacean (lobster), and finfish (Atlantic salmon)—representing commercially important 

seafood types. Oysters (Crassostrea gigas) size #1 were obtained from Westcott Bay 

Sea Farms, Friday Harbor, Washington. Two sizes of Atlantic salmon (Salmo salar)—2 

lb. fish for the diesel exposure and 1 lb. fish for the Monterey Crude oil exposure—were 

obtained from Northwest Seafarms, Bainbridge Island, Washington. The lobsters 

(Homarus americanus), weighing 1 to 1.25 lbs. each, were shipped from Gloucester, 

Massachusetts. 

• The diesel exposure tank contained 46 salmon, 40 lobsters, and 240 oysters 

(assuming 6 oysters/sample) to obtain the required 25 to 30 samples per species. The 

control tank contained 25 salmon, 20 lobsters and 120 oysters. 

• The Monterey Crude exposure tank contained 40 salmon, 40 lobsters, and 240 

oysters. The control tank contained of 35 salmon, 20 lobsters and 120 oysters. 

The surplus specimens were to allow for incidental mortality during transportation and 

exposure, and for monitoring of baseline contamination and uptake during the exposure. 

91 
The control tanks were used to rule out any flavors or odors that might be artifacts of our 

facility (e.g., from the water or the tanks) and to serve as controls for chemical analysis. 

The control organisms (3 species) were held in an 8-ft circular tank (4981.6 L), and the 

exposed organisms (3 species) were held in a 12-ft circular tank (10129.2 L). A PVC 

liner was used to prevent oil contamination of the aquaculture facilities' tanks. All three 

species were allowed to acclimate for at least 24 hours in their respective tanks (under 

flow-through conditions) before exposure. Exposure consisted of 48-hour static-water

exposure with aeration and a single addition of the petroleum product to yield a nominal 

concentration of 25-ppm (w/v). Approximately 250 g of the diesel or Monterey Crude oil 

were weighed out in a beaker. At the beginning of the exposure, water flow and aeration 

were turned off and the petroleum product was poured onto the water surface. For 

diesel oil, the beaker was rinsed several times in the tank water to complete the transfer, 

and the aeration was then resumed. For the crude-oil exposure, the oil had to be 

scraped out of the beaker to complete the transfer. The aeration system was used to: 1) 

circulate the petroleum product in the tank, 

2) simulate water conditions characteristic of near shore exposure, where wave action 

and mixing are an important part of the exposure conditions, as well as 

3) maintain the system-dissolved oxygen during the static exposure. 

At the end of the 48-hour exposure, the animals were sacrificed. Salmon were filleted, 

skinned, wrapped in aluminum foil, and vacuum-packed before storing at -20° C. Whole 

lobsters and oysters in the shell were wrapped in aluminum foil and vacuum-packed 

before storing at -20° C. 

92 
APPENDIX 8

Using Random Code Numbers and 

Random Sample-Presentation Methods

Random code numbers are those code numbers that cannot be predicted, based on the 

numbers already seen in the sample series, 

and that bear no relationship to any variable within the samples. 

An example is shown in a series that can be predicted and one that cannot, where a coin is 

tossed and, assuming that 0 = heads and 1 = tails, these series become: 

predictable series. . . coin 0 1 0 1 0 1 0 1 0 1 0 1. . . . . . . . .

unpredictable series. . . coin 1 1 0 0 0 1 0 1 0 1 1 1 0 1 1 0 0 1 0 0 0 0 1. . . . . . . . 

Random numbers are used in sample presentations to 1) prevent assessors from 

predicting information about the samples, and 2) control the occurrence of errors of expectation. 

Information about samples can be inadvertently given from factors such as 

• the order in which samples are presented, 

• the code numbers assigned to the samples, or 

• extraneous information about the samples that have been given before the evaluation 

sessions. 

Also, seemingly predictable codes can provide false information that creates confusion in a 

test. These errors are generally not an issue when the evaluators are professional sensory 

analysts who have been calibrated and tested. However, these errors are significant when 

selecting assessor trainees and testing trained sensory panels. 

These presentations are appropriate for both expert and trained assessors to demonstrate 

the validity of the test method. 

The randomization process 

1. Assigning code numbers to the sample. In this case, 3-digit random number 

codes are used. This is common practice in sensory testing, as 3-digit codes generally have no 

meaning to the assessors. (However, there may be occasions where 3-digit codes do have 

meaning to the assessors in the context of the samples. In this case, using 4-digit codes will 

93 
generally remove the difficulty.) 

2. Assigning random presentation sequences for the samples. This reduces any 

effect of sample order or carryover effect from one sample to another. Each assessor examines

the samples in a different sequence from the others. This is done when testing both expert and 

trained assessors. 

Generating 3-digit code numbers

• Examples of predictable coding that should not be used. Using a meaningful code within 

the sample number, e.g., the middle number: 

113 219 817 blank (water) 

321 726 429 low-concentration salt 

138 432 635 high-concentration salt 

• Examples of unpredictable coding as it should be used. An appropriately coded series 

would be given by no meaningful numbers: 

726 255 979 blank (water) 

368 417 182 low-concentration salt 

631 118 229 high-concentration salt 

• Random 3-digit number codes are easily generated in different ways: 

1. Using the random number table, found in the tables section of most sensory analysis 

texts and statistics texts. A starting point within the table is arbitrarily selected, and random 

codes are written from that point. Resulting codes should be checked so that no accidental 

patterning occurs and so that no repeat codes are generated. 

2. Using a random code set, i.e., a prepared set of all the 3-digit codes from 001 to 999 on 

separate cardboard disks (or other convenient medium). The codes are drawn from this set 

without replacement, to ensure that no repeat codes are generated. The resulting number 

set should be checked for any accidental patterning. 

1. By computerized random number generation within a software package, e.g., Excel. This is 

the easiest way to generate a large set of random numbers; the sort function can be used to 

check for any repeat codes. 

94 
Generating random 3-digit numbers using Excel. 

This method will generate a set of 3-digit random codes with no repeats for use in coding 

samples for sensory studies. The codes act to remove identity from the sample for presentation 

to sensory panelists, but still provide a method for tracking samples within a study. 

A. Generating the random number set: 

1. Using “TOOLS” > “DATA ANALYSIS” > “RANDOM NUMBER GENERATION”, generate 

the set of three digit codes needed. 

Settings: 

No. of variables = 1. 

No. of random variables = (as needed). 

Distribution = uniform. 

Between 1 and 999 (or 100 and 999 if numbers below 100 are not needed). 

Random seed = choose one as needed. 

Output range = as needed (Column A, here). 

2. Format the code numbers using “FORMAT” “CELL” “NUMBER” “CUSTOM” to 000 (so 

that 1 to 99 will appear as 3 digits).

3. Adjust the values of the numbers generated in the worksheet using “TOOLS” > 

“OPTIONS” > “CALCULATION” and check “precision as displayed”, and “OK” to loosing 

the accuracy with the numbers. (This gets rid of hidden decimal places that interfere 

with the sorting process). 

B. Now begin the process of checking for duplicates by:

4. Enter “1” in the first cell of Column B. Number the codes from 1 to X (here = 100) in 

column B (so that they can be put beck in random sequence after checking duplicates). 

Do this with “EDIT” > “FILL” > “SERIES” > “COLUMNS” (step value = 1, stop value = N, 

(hers, 100)). 

5. Use “DATA” > “SORT” by Column A to put the random numbers in order.

6. Place the cursor in the first cell of Column C. Using the “Function Wizard” icon, call up

the IF statement, and enter the formula to test for repeat numbers into Column C, with 

“a1 = a2, if true = 1, if false = 0”. Copy this statement down the full length of Column C. 

95 
7. Check Column C for any 1’s. Correct and duplications (i.e. change them appropriately). 

(By entering a “Σ” command at the base of Column C, the number of duplicates which 

must be corrected will be shown. As they are corrected, this number will reduce to “0”). 

8. Use “DATA” > “SORT” by Column B to put the codes back in random order. Assign 

them to samples as needed.

96 
APPENDIX 9

Example of expert assessor training data 

(from NOAA Seafood Safety Workshop, May 1999, Seattle, WA).

Summary scores following brief (8-hr) training period. Sample Key Salmon # Oysters # Lobster # Overall % AssessorC = Control (no exposure) C D C M Correct C M D C Correct D C M D Correct Correct #D = Diesel fuel exposure 0 2 0 3 4 0 3 3 0 4 2 0 2 3 4 100.00 5 M = Monterey Crude oil exposure 0 1 0 3 4 0 2 2 0 4 3 0 3 2 4 100.00 7 

0 2 0 2 4 0 1 2 0 4 2 0 1 2 4 100.00 80 2 0 1 4 0 1 3 0 4 3 0 1 3 4 100.00 11

Score Intensity Key 0 1 0 1 4 0 1 2 0 4 2 0 2 3 4 100.00 120 = no contamination 0 2 0 3 4 0 3 2 0 4 3 0 2 3 4 100.00 13 1 = very slight 0 1 0 2 4 0 1 2 0 4 2 0 2 2 4 100.00 15 2 = slight contamination 0 2 0 2 4 0 1 2 0 4 2 0 2 2 4 100.00 16 3 = moderate contamination 0 2 0 3 4 1 1 1 0 3 2 0 2 3 4 91.67 1 4 = strong contamination 0 2 0 2 4 0 2 3 0 4 3 0 0 3 3 91.67 3 

0 1 0 2 4 0 2 2 0 4 2 0 0 3 3 91.67 60 2 0 1 4 0 1 3 0 4 3 0 0 1 3 91.67 10

0 1 0 3 4 0 1 1 0 4 3 0 0 3 3 91.67 141 0 0 2 2 0 2 2 0 4 3 0 1 2 4 83.33 41 1 0 2 3 0 1 2 0 4 1 0 0 1 3 83.33 170 3 0 2 4 1 0 2 0 2 2 0 0 1 3 75.00 21 0 0 2 2 0 3 3 0 4 3 0 1 0 3 75.00 9

Average petroleum intensity 0 1 0 2 3.79 0 2 2 0 3.85 2 0 1 2 3.584 92.65 Group Avg.Total hits in 17 evaluations 3 15 0 17 2 17 17 0 17 0 11 16 These data are from a training workshop using known samples. Participants were seafood inspectors or seafood researchers. For anactual oil-spill situation, you would select those assessors scoring 100%, if possible, or at least 90%. When using assessors for seafood 

testing who score less than 100%, you may want to increase the number of assessors. 
98 
APPENDIX 10

NOAA/NMFS NATIONAL SENSORY SECTION 

CHAIN OF CUSTODY FORM 

7600 Sand Point Way NE, Seattle, WA 

For more information contact Michael DiLiberti 

978-281-9123 or FAX 978-281-9125 

Project___________________ Sampler________________________ 

Sample 

I.D. #

Date 

Collected 

Location Sample Type

(Tissue, oil, water. 

Include species name

and tissue type)

Comments

    

    

    

    

    

    

    

    

    

    

  

    

Collected by: (signature) Received by:(signature) Condition: Date/Time 

Relinquished by: (signature) Received by:(signature) Condition: Date/Time 

Relinquished by: (signature) Received by:(signature) Condition: Date/Time

* If shipped, include carrier name and copy of shipping invoice 

99 
Chain of Custody Procedures 

BACKGROUND

The NOAA Damage Assessment Center (DAC) has established chain of custody 

procedures for those personnel collecting field data. This document is a record of the 

methods used to handle samples collected for the damage assessment process, which 

may become evidence in a court of law. 

The procedures outlined in this document represent one acceptable method. The failure 

in any particular instance to follow one or more of the steps listed here does not 

necessarily render evidence either inadmissible or unusable, however, field personnel 

should inform either the Damage Assessment Center or its attorneys about any 

deviation from procedures specified in this document. All that the Courts require is that 

the sample itself (or results of its analysis) be adequately authenticated to assure that 

what occurs in court replicates circumstances existing at the sample-taking location. No 

defendant or respondent may claim as a defense or an objection any deviation from 

procedures described in this memo. 

DEFINITION OF CUSTODY

"Chain-of-custody" procedures are followed to "authenticate" a sample from the time it is 

taken until the results are introduced as evidence into court. A sample is in your 

"custody" when: 

1. It is in your actual physical control and presence. 

2. It is in your view. 

3. It is not in your physical presence but is secure in a place of storage to which 

only you have access. 

4. It is not in your view or physical presence but is secured in a place of storage 

to which only you and identified others have access. 

SAMPLE COLLECTION

1. As few people as possible should handle the sample from its taking through 

laboratory analysis. 

2. Preprinted DAC samples tags should be used to identify each sample. These are 

filled out in waterproof ink and attached to the sample container at the time the complete 

sample is collected. The preprinted tags contain the following information: sample #, 

contents, preservative, time/date of collection, location, and collector. A witness who 

has observed the samples being taken should also include his/her name on the sample. 

The sample tags are records made in the usual course of regularly conducted official 

activity and may constitute past recollection recorded. When tags are completed, the 

collector should not leave any blanks thereon unfilled. 

100 
3. Blank samples using water prepared specifically for the sample collector should be

used on a sampling project, and should be analyzed later to establish the lack of 

contamination by the sampling device, the container, or any preservatives used. 

4. Field Data Record logbooks with numbered pages should be used to record field 

measurements and other pertinent information. These notes will be used to refresh the 

sample collector's memory in the event he/she later testifies regarding his/her actions. 

The original or first impression copy of these field data sheets, chain-of-custody sheets, 

and analysis requested sheets should be sent along with the samples. Data entered in 

the logbooks or forms are recorded with ballpoint pen or waterproof ink. Each page is 

signed by the sample collector and any available witness. The preparation and custody 

of the logbooks during the survey are the responsibility of the survey coordinator. Once 

the survey is complete, field data logbooks and data forms are to be retained by the 

survey coordinator or a designated representative. Any errata in entries should be lined 

out with a single line and initialed and dated so a later reader can read what was written 

before the correction. 

5. The sample collector is responsible for the care and custody of the samples until they 

are properly dispatched to the receiving laboratory or turned over to an assigned 

custodian or courier. The sample collector must assure that each sample is in his/her 

"custody" so no one can tamper with it. 

6. If colored slides, photographs, or other related evidence are obtained to show the 

impact of the pollutant or substantiate any other conclusions of the investigations, the

following documentation should be on the back of the photo or in the field data logbook: 

time, date, site location, and the signature of the photographer and any witness. Film or 

other materials of this nature which may be used as evidence, may also (but need not) 

be handled using chain-of-custody procedures. 

TRANSFER OF CUSTODY AND SHIPMENT 

1. Collected samples are to be accompanied by a chain-of-custody record that includes 

the name of the survey, sample collector's initials, laboratory sample number, and 

number of containers. When turning over the possession of a part or all of the samples 

to a field analysis station or to a laboratory, the transferor and transferee should sign and 

record the time and date on the sheet. 

2. All packages are to be accompanied by the chain-of-custody record identifying the 

contents. The original accompanies the shipment, and a copy is retained by the survey 

coordinator. The chain-of-custody record is signed by the collector along with recording 

the date and time. It is then placed inside the shipping container along with the Field 

Data Sheet and Analysis Requested Sheet. 

3. Samples are to be packed and sealed for shipment in suitable containers to avoid 

damage. A sample seal should be attached across the lid of each shipping container in 

such a manner that the container cannot be opened without breaking the seal. This lock 

and/or seal is not to be removed until the shipping container is opened by the laboratory 

custodian or a designee.

101 
4. If sent by mail, the package is sent via Registered Mail with Return Receipt 

Requested. If sent by common carrier, all shipping receipts should be retained as part of 

he permanent chain-of-custody documentation. 

5. Couriers picking up samples at the airport, post office, etc. should sign the shipping 

documents to acknowledge receipt of the samples. 

LABORATORY CUSTODY PROCEDURES 

The following procedures should be followed regarding the handling and custody of 

samples in the laboratory. In any given instance, an assistant may perform any item

indicated below, but a record should be made of the assistant's participation. 

1. A designated custodian should: 

a. Accept and receive custody of the shipped samples. 

b. Observe the physical condition of the shipping container noting any 

broken seals or indications of any tampering. 

c. Open the shipping container (and at his/her option saving or not saving 

any seals or stickers on that container). 

d. Crosscheck and verify the information on the chain-of-custody receipt 

with the tags or other markings on the sample containers. 

e. Make appropriate entries in the chain-of-custody receipt making sure 

the identity of the courier is reflected.

f. Enter or have an assistant enter the information contained on the 

sample tags and/or markings on the field data sheet and on the analysisrequested sheet, into a bound logbook. 

g. Place all of the received samples in an appropriate storage area that is 

capable of being secured against access whether or not the access to the 

building is secured. 

2. A designated person should routinely be in charge of distributing samples to 

the appropriate analysts, or each analyst should be in charge of collecting his/her 

samples from the storage area. In any event, the person performing that activity 

should be identified in the analysis records for each sample.

3. When not needed or being used in the laboratory for analysis, the unused 

portion of the sample should be returned to its storage area. 

4. All identifying tags, seals, or stickers from the sample container should be 

retained with the analysts notes and other analysts documents. 

5. Each analyst is responsible for the care and custody of each sample received 

by him/her for analysis form the time of receipt until the sample is exhausted or 

returned to its storage area. Samples should be returned to a storage area by 

102 
the analyst who analyzed the sample, and the analysts' records for the sample 

should record any deviation from that practice. 

6. The laboratory director should obtain authorization from the project 

coordinator and case attorney for sample disposal for civil cases. No criminal 

cases samples are to be disposed of until the case is closed and all appeals 

have been heard. The prosecuting attorney must be consulted prior to disposal 

of any evidence for criminal cases. 

LABORATORY DOCUMENTATION

The procedures generally recognized by professional chemists and laboratories 

for documenting their work are acceptable for documentation in laboratories 

contracted by DAC for damage assessment work. 

All sample data, laboratory observations, and calculations will be recorded in 

logbooks or in bench sheets. Each lab document should, on its first page, reflect 

the project number, date of composing, names of analysts and assistants 

participating, and any other information concerning the identity of the sample 

analyzed. Any document reflecting results of analysis should have similar 

identifying data on the first page. Charts or printouts from instrumentation, 

graphs, and similar "display" type documents should have similar identifying 

information affixed to them. Both draft and smooth copies of any such 

documents should be retained as part of the lab documentation. 

Correspondence, report notes, methods, references, sample inventories,

checkout logs, etc. should be part of the permanent lab records. 

Any logbook or bench sheet needs to contain (1) clear identification of who made 

what entries on the same, and (2) information sufficient to enable the entrymaker to recall and describe each step of the analysis performed. The analyst 

and his/her assistants may be called upon to testify in subsequent legal 

proceedings about the analysis performed and results obtained. In addition, 

procedures followed if it became necessary for that to be done. Irregularities (if 

any) observed during the analytical process should be noted. If, in the 

professional judgement of the analyst, a deviation from a particular analytical 

method is advisable or used, the deviation should be described and the reasons 

for that deviation should be recorded. 

Logbooks or comparable permanent records must be kept which reflect each 

instance in which lab instruments or instrumentation is calibrated. Such records 

are the very foundation of the later analytical work performed, and are critical in 

any later legal proceeding. 

Any continuous monitoring records (e.g. charts showing temperatures of storage 

cabinets where some samples are stored) should be kept for some years. 

Before a final lab report is sent out, the lab personnel will assemble and crosscheck information on sample tags, custody records, bench sheets, analysts' 

logbooks and/or notes, and in any relevant permanent records to ensure that 

103 
data pertaining to each particular sample is consistent throughout all lab 

documents. 

104 
APPENDIX 11 

Evaluating Expert Assessor Training Using Fisher’s Exact Test

Following training, it may be necessary to validate the performance of the expert 

assessors before beginning evaluations of the samples taken from the spill and control 

sites. 

The following procedure can be applied after training or re-familiarisation of expert 

assessors with defects caused by petroleum contamination. It can be used with known 

samples, so there is an actual right or wrong answer associated with each sample. It 

allows the calculation of the exact probability of the results a test set of samples and 

shows the minimum number of samples needed for the selected level of p = 0.999 for 

testing of significance. The method used is Fisher’s Exact Test as described by Hays 

(1994)1

. 

The null hypothesis for the test is that the data is random in nature and the alternate 

hypothesis is that it is not. The probability calculated is then the indication of the chance 

that the results given by that assessor were only random in nature. 

The data is recorded in a table as shown below. 

Known Condition of Assessor’s Responses 

Samples Taint present Clear (no taint present) Total 

Tainted samples a b a + b 

Clear samples c d c + d 

Total a + c b + d N 

This is essentially finding the probability that the particular result or any result less likely 

is due to chance. This is calculated using the following formula and may be done using 

a hand-held calculator or by programming the calculation into an Excel spreadsheet. 

p (obtained table) = (a+b)! (c+d)! (a+c)! (b+d)!*

 (N! a! b! c! d!) 

For example, if the expert assessors are presented with 40 samples (20 clear controls 

and 20 exposed to taint) and the following data are obtained 

Known Condition of Assessor’s Responses 

Samples Taint present Clear (no taint present) Total 

Tainted samples 17 3 20 

Clear samples 1 19 20 

Total 18 22 40

p (obtained table) = (20)! (20)! (18)! (22)! = 2.011 x 10-7 (or 0.0000002011)

 (40! 17! 3! 1! 19!) 

 

 1

 Hayes, William L. 1994. Statistics. Harcourt Brace College Publishers, New York. pp. 863-

865. 

105 
In order to evaluate the results, a “cut-off” of an acceptable probability of chance must be 

selected. In this case, p = .001 (or 1.0 x 10-3) is being used. This means there is less 

than 1 chance in 1000 that the results are due to chance and the ability of the expert 

assessor to evaluate the samples is validated. The results in the example show 2 

chances in 10 million that the results are due to chance (or 1 chance in 5 million). 

The following gives examples of data collected and the calculations based on each. 

These examples show that if a minimum number of 20 samples are used (10 clear and 

10 tainted), the pattern of results (calculated as shown in the above tables) gives 

assurance at P<0.001 that the expert assessor can correctly identify taint when it is 

present in the samples. If more samples are used, the formula given above can be used 

to calculate the results for any data set. 

Example 1. 

Known Condition of Assessor’s Responses 

Samples Taint present Clear (no taint present) Total 

Tainted samples 9 1 10 

Clear samples 1 9 10 

Total 10 10 20

p (obtained table) = (10)! (10)! (10)! (10)! = 0.00054

 (10! 9! 1! 1! 9!) 

Example 2. 

Known Condition of Assessor’s Responses 

Samples Taint present Clear (no taint present) Total 

Tainted samples 8 2 10 

Clear samples 0 10 10 

Total 8 12 20

p (obtained table) = (10)! (10)! (8)! (12)! = 0.00036

 (10! 8! 2! 0! 10!) 

Example 3. 

Known Condition of Assessor’s Responses 

Samples Taint present Clear (no taint present) Total 

Tainted samples 10 0 10 

Clear samples 2 8 10 

Total 12 8 20

p (obtained table) = (12)! (8)! (10)! (10)! = 0.00036

 (10! 0! 10! 2! 8!) 

 

Explanatory Note on the use of Factorial Notation: The notation “!” means the 

factorial of the number, e.g. 4! = 4 x 3 x 2 x 1 = 24. When using a hand-held calculator, 

the usual algebraic “cancelling” of numbers in the numerator can be done and then the 

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value for p calculated. It must be remembered that, e.g. 20! divided by 17! would leave 

20 x 19 x18 in the numerator and 20! / 19! would leave 20 in the numerator, etc. This 

does not have to be done if the calculation is programmed into Excel. 

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