1

This guidance 

document is designed 

to help very small 

meat and poultry 

establishments that 

manufacture jerky 

identify:

• The key steps in 

the jerky process 

needed to ensure 

safety; and

• The scientific 

support 

documents 

available to help 

develop a safe 

process and 

product.

 

 

 

 

FSIS Compliance Guideline for Meat 

and Poultry Jerky Produced by Small 

and Very Small Establishments 

2012 Updated Compliance Guideline 
2

This Compliance Guideline articulates how industry can meet FSIS expectations 

regarding jerky processing. It is important to note that this Guideline represents FSIS’s 

current thinking on this topic and should be considered usable as of its issuance. 

Guidelines will be continually updated to reflect the most current information available to 

FSIS and its stakeholders. 

Request for comments:

FSIS is seeking comments on this guidance document as part of its efforts to 

continuously assess and improve the effectiveness of policy documents. All interested 

persons may submit comments regarding any aspect of this document, including but not 

limited to: content, readability, applicability, and accessibility. The comment period will 

be 60 days and the document will be updated in response to the comments.

Comments may be submitted by either of the following methods:

Federal eRulemaking Portal Online submission at regulations.gov: This Web site 

provides the ability to type short comments directly into the comment field on this Web 

page or attach a file for lengthier comments. Go to http://www.regulations.gov and 

follow the online instructions at that site for submitting comments.

Mail, including - CD-ROMs, and hand- or courier-delivered items: Send to Docket 

Clerk, U.S. Department of Agriculture (USDA), FSIS, Patriots Plaza 3, 1400 

Independence Avenue SW, Mailstop 3782, 8-163A, Washington, DC 20250-3700.

All items submitted by mail or electronic mail must include the Agency name, FSIS, and 

document title: FSIS Compliance Guideline for Meat and Poultry Jerky Produced by 

Small and Very Small Establishments. Comments received will be made available for 

public inspection and posted without change, including any personal information, to 

http://www.regulations.gov.
3

Compliance Guideline for Meat and Poultry Jerky Produced by Small 

and Very Small Establishments 

Table of Contents

 

Purpose 4

Background 4

Step-by-Step Guide for Jerky 

Processing 

5

Critical Operational 

Parameters during the 

Lethality Treatment

8 

Scientific Support Documents 

Available for Jerky Processing

14

References 20

Helpful Websites 21

Attachment 1: Time, temperature, 

and humidity combinations reported 

in the literature for beef jerky that 

achieve at least a 5 log reduction in 

E. coli O157:H7

23

Attachment 2: Making Your Own 

Wet-bulb

(Reprinted with Permission from the 

University of Wisconsin)

32
4

Compliance Guideline for Meat and Poultry Jerky

Produced by Small and Very Small Establishments 

Purpose

This guidance document is designed to help very small meat and poultry 

establishments that manufacture jerky identify:

• The key steps in the jerky process needed to ensure safety; and

• The scientific support documents available to help develop a safe 

process and product.

This guidance document is not intended to set any regulatory requirements. This 

document replaces previous versions of the guidance that was last updated in 2007.

Background

Meat or poultry jerky is a ready-to-eat (RTE), dried product that is considered shelfstable (i.e., it does not require refrigeration after proper processing). Following a 2003

salmonellosis outbreak from Salmonella Kiambu in jerky produced in New Mexico, FSIS 

published the first version of the Compliance Guideline for Meat and Poultry Jerky 

Produced by Small and Very Small Establishments. The Compliance Guideline 

provided guidance for small and very small meat and poultry establishments on the 

critical steps for jerky processing and the controls needed at each of these steps to 

ensure a safe product was produced. 

One potential cause of the 2003 Salmonella

Kiambu in jerky outbreak was the very slow 

drying process under low humidity conditions 

(1% RH - 82°C dry bulb, 30°C wet bulb), 

which allowed Salmonella organisms to 

dehydrate during drying and become 

resistant to heat1

. Therefore, the first version 

of the jerky compliance guidelines 

emphasized the need for high levels of 

humidity during jerky processing. Since 

2003, a number of journal articles have been published that has increased scientific 

understanding of the critical factors during jerky processing including the role of 

humidity. 

This document updates and replaces the 2007 version of the guidance to reflect the 

most up-to-date science and understanding of jerky processing. In addition, through 

recent Food Safety Assessments (FSAs), FSIS has found that producers of meat and 

poultry jerky may still not be adequately processing jerky to achieve the lethality 

necessary to produce a safe product. Therefore, this guidance also addresses recent 

concerns identified through FSAs. 

 

1

http://www.promedmail.org/direct.php?id=20031003.24887 

One potential cause of the 2003 

Salmonella Kiambu in jerky outbreak 

was the very slow drying process 

under low humidity conditions
5

Step-by-Step Guide for Jerky Processing

Below is a summary of the seven (7) general or common processing steps used in jerky 

production. Although an establishment’s process may not include all these steps, the 

lethality treatment and drying should be utilized to produce a safe product. Other 

steps such as the intervention and post-drying steps may be utilized for those 

processes that do not achieve an adequate lethality. Further descriptions of the key 

steps in the jerky process including the microbial interventions that can be applied to 

ensure safety, are reviewed on the following pages. 

 Step 1 - Strip preparation: Whole muscle is sliced or ground; ground product is 

formed into strips (some jerky is formed).

 Step 2 – Marination: The strips are then marinated in a solution that often 

contains salt, sugar, and flavoring ingredients.

 Step 3 – Interventions: Antimicrobial interventions, before and after marinating 

the strips of raw product, may be added to increase the level of pathogen 

reduction beyond that achieved by heating alone. 

 Step 4 – Lethality: The lethality treatment is 

defined as the process step or steps used to destroy 

pathogenic microorganisms on or in a product to 

make the product safe for human consumption and 

is considered to include the time when the product is 

placed in the heated oven until the product reaches 

the desired lethality time/temperature combination 

(also referred to as the cooking time). 

In order to achieve adequate lethality, it is important 

that an establishment’s actual process adheres to 

the following critical operational parameters (see key 

definitions on page 7) in the scientific support 

documentation: 

• Product time/temperature combination

• Relative humidity

 Step 5 – Drying: Drying is the process during which water (moisture) is 

removed from the product. After the lethality treatment, jerky is dried to meet a 

water activity level sufficient for food safety purposes.

 Step 6 – Post-drying heat step: A post-drying heat step may be added to 

increase the level of pathogen reduction beyond that achieved by heating alone.

 Step 7 – Handling: Product is often handled after the lethality and drying steps

and prior to packaging.

The purpose of the lethality 

step is to apply a lethality 

treatment to kill or reduce the 

level of microorganisms. 

Drying the jerky ensures the 

final product reaches a 

sufficient water activity to 

prevent the growth of 

microorganisms, especially 

toxigenic microorganisms, 

such as Staphylococcus 

aureus. 
6

Each step in the jerky process is reviewed in more detail below. Please note that each 

process is unique, so some processors may not utilize all 7 steps or some may perform 

the steps below in different orders. 

 Step 1 - Strip preparation: Whole muscle is sliced or ground; ground product is 

formed into strips (some jerky is formed). 

It is critical for establishments to use source materials prepared under good 

manufacturing practices (GMPs) designed to minimize contamination and the presence 

and growth of pathogens of public health concern so that the initial pathogen load is not 

higher than what the process is designed to reduce. Establishments that choose to 

purchase source materials known to be contaminated with pathogens of public health 

concern, such as Salmonella or shiga toxin-producing Escherichia coli (E. coli) (STEC)

organisms such as E. coli O157:H7 or E. coli O45, should have controls in place to 

ensure cross-contamination between raw and RTE product does not occur. 

 Step 2 – Marination: The strips are then marinated in a solution that often 

contains salt, sugar, and flavoring ingredients. 

 Step 3 - Interventions: Antimicrobial interventions, before and after marinating 

the strips of raw product, have been shown to increase the level of pathogen 

reduction beyond that achieved by heating alone. 

Some heating processes may not deliver an adequate lethality and, thus, may require 

an additional intervention step to ensure product safety. Examples of interventions that 

may increase the lethality of the process are: 

• Preheating the meat or poultry jerky strips in the marinade to a minimum 

internal temperature of 160°F will provide an immediate reduction of 

Salmonella (Harrison and Harrison, 1996). Heating in marinade may produce 

unacceptable flavors for some products; however, other liquids such as water 

could be used. The times and temperatures in FSIS Appendix A: Compliance 

Guidelines For Meeting Lethality Performance Standards For Certain Meat 

and Poultry Products (referred to throughout the document as Appendix A) 

could be used for preheating in the liquid, although the product internal 

temperature should be monitored to ensure adequate lethality is achieved). 

• Dipping the product in 5% acetic acid for 10 minutes before placing it in the 

marinade can augment the log reduction effects of drying but not enough to 

eliminate pathogens (Calicioglu, 2002 & 2003). This intervention may also 

result in an undesirable flavor. 

• Dipping the product in 1:2 or 1:3 mixtures of calcium sulfate (Mionix 

Safe

2

OTM) and water for 30 seconds can better reduce the level of 

Salmonella, Listeria monocytogenes (Lm), and E. coli O157:H7 compared

with no pretreatment. Pretreatment with acidified sodium chlorite (Keeper®) at 

concentrations between 500 and 1,200 ppm was also effective. These 

pretreatments were effective in both dehydrators and smokehouse processing 

(Harrison et al., 2006). 
7

 Step 4 - Lethality treatment: 

The establishment needs to control, reduce, or eliminate 

the biological hazards identified in its hazard analysis. For 

meat and poultry jerky, these hazards will most likely 

include microbiological hazards from Salmonella spp., Lm, 

and Staphylococcus aureus. For beef jerky, E. coli

O157:H7 may also be a hazard reasonably likely to occur. 

In recent years, several jerky products have been found to 

be adulterated with Salmonella and E. coli O157:H7.

The lethality treatment of poultry jerky must achieve at least 

a 7.0 log reduction of Salmonella spp. as required in 9 CFR 

381.150. The lethality treatment of meat jerky should

achieve at least a 5.0 log reduction of Salmonella spp. and 

should also achieve sufficient reductions in the other 

bacterial pathogens of public health concern (e.g., at least 

a 5.0 log reduction for E. coli O157:H7 for products 

containing beef as recommended in the Salmonella

Compliance Guidelines for Small and Very Small Meat and 

Poultry Establishments that Produce Ready-to-Eat (RTE) 

Products). In addition, the lethality treatment of meat and 

poultry jerky should achieve at least a 3.0 log reduction in

Lm although a 5.0 log reduction or greater is desirable for 

providing an even greater safety margin for ensuring that 

Lm doesn’t grow during cold storage to detectable levels. 

However, establishments are not expected to validate that 

their process achieves reduction in Lm if it achieves 

sufficient reductions in Salmonella because Salmonella is 

considered an indicator of lethality. 

In addition, an official establishment should have sound 

decisions in the hazard analysis that support that source 

materials were prepared using GMPs and other process 

controls such that adequate reduction results in the 

production of a safe product.

Official establishments choosing to use cooking to achieve 

lethality before drying may consider a number of different 

types of scientific documents to support the 

time/temperature/humidity combination used in the actual

process. Such types of scientific support documents

include: 

• Compliance Guidelines (e.g., Appendix A) 

• Journal articles 

• Challenge studies 

• In-plant data 

KEY DEFINITIONS

The lethality treatment is 

defined as the process step or 

steps used to destroy 

pathogenic microorganisms on 

or in a product to make the 

product safe for human 

consumption and is 

considered to include the time 

when the thermal processing 

begins (e.g., the product is 

placed in the heated oven) 

until the product reaches the 

desired lethality 

time/temperature combination 

(also referred to as the 

cooking time).

Critical operational 

parameters are those 

parameters of an intervention 

that must be met in order for 

the intervention to operate 

effectively and as intended. 

Such parameters include but 

are not limited to time, 

temperature, water activity,

concentration, relative 

humidity, and type of 

equipment. 
8

An in-depth discussion of considerations for each of these types of scientific support 

documents, along with examples, is discussed in the section titled: Scientific Support 

Documents for Jerky Processing. 

Critical Operational Parameters during the Lethality Treatment

Regardless of the scientific support document utilized, it is important that an 

establishment’s actual process and procedures relate and adhere to the critical 

operational parameters in the scientific support in order to achieve adequate lethality.

There are several critical operational parameters that are important for jerky processing

that will be reviewed. 

Product time/temperature combination

It is important that the jerky product achieve the temperature shown to be effective in 

the Appendix A guidelines or other

scientific support documents. Most often 

the temperatures used during the 

lethality treatment that are reported in 

scientific support documents are the 

temperatures that the product should 

reach. 

Product internal temperature can be 

measured by inserting a thermocouple 

probe into the geometric center of a beef 

strip. Proper insertion may be difficult 

because the product is so thin; therefore, 

FSIS recommends that establishments 

slice one piece of jerky twice as thick as 

normal so that the probe can be inserted. 

If this thicker piece reaches the lethality 

temperature, the thinner pieces should 

as well. In addition, to accurately 

measure the product temperature, the 

establishment should also have an 

understanding of factors that could affect the temperature of the product. These factors 

include having an understanding of the cold spots in the oven, as well as understanding 

of the variation in temperature of the oven during different seasons. Although 

monitoring product temperature is encouraged, establishments can use the oven 

temperature in place of the product temperature provided that the establishment has a 

consistent product and process and has sufficient data correlating the oven temperature 

with the product temperature.

In addition to the product temperature, the amount of time the product is held at this 

temperature is also critical to ensuring that adequate lethality is achieved. It is 

important for the establishment to understand how the actual temperature of the product

was taken, the time it takes the product to reach the target temperature (known as the 

come-up time or CUT), and the amount of time the product is held at the target 

temperature compared to the scientific support documentation. If the product is held at 

FSIS has found through FSAs that many 

establishments often use temperatures from 

support documents to set critical limits for the 

oven temperature; however, setting the oven 

temperature to the temperature in the support 

does not ensure that the product will reach the 

same internal temperature which is critical to 

ensuring adequate lethality is achieved. FSIS 

has also found through FSAs that some 

establishments do not measure or verify that 

the product has achieved the desired internal 

lethality temperature until after drying. FSIS 

does not recommended verifying product 

temperatures only after drying because the 

product may have dried out before the lethality 

temperature was reached resulting in lower 

than expected pathogen reduction.
9

Without sufficient humidity the product surface may dry too 

quickly, and the bacteria may become more heat resistant. 

the target lethality treatment for less time than what was 

used in the scientific support then adequate lethality may

not be achieved. 

Relative Humidity

In addition to the product time/temperature combination, the 

relative humidity (e.g., steam) in the oven is also critical for 

achieving adequate lethality in jerky. It is important that the 

establishment maintains humidity according to Appendix A 

or other supporting documents. Relative humidity around a 

product during the lethality treatment promotes lethality in 

two ways: 

• First, the humidity reduces surface evaporation and 

the energy or heat that evaporation removes from the 

product during heating. If sufficient relative humidity 

surrounding the product is not maintained during the 

lethality treatment, undesirable evaporative cooling at 

the surface will occur, and the product will not reach 

the desired temperature. Producing products under 

conditions of high humidity early in the cooking 

process reduces evaporative cooling allowing 

products to reach higher product surface 

temperatures which results in a greater reduction in

microorganisms. 

• Second, the humidity keeps the product surface (and 

any pathogens) more moist and prevents unwanted 

concentration of solutes (e.g., sugar and salt) as a 

result of drying. Research has demonstrated that 

bacteria can become more heat resistant as their 

moisture level decreases, and increased concentrations of solutes, especially 

sugars, increase the heat resistance of bacteria. Therefore, drying of the product 

surface before the pathogens are destroyed will increase pathogen heat 

resistance and allow them to survive the heating process. By incorporating 

humidity to minimize evaporation, the D values (time at a constant temperature 

necessary to destroy 90% or 1 log10 of the target organism) that are the basis for 

Appendix A and other scientific support documents remain valid (Goepfert, 1970; 

Goodfellow and Brown, 1978; Faith, N.G. et al. 1998).

For these reasons, it is crucial that the processor prevent drying of the product until a 

lethal time-temperature combination is attained. Therefore, in order to be most effective, 

KEY DEFINITIONS

Relative Humidity is defined 

as the degree of saturation of 

the air by water (vapor), 

expressed as a percentage. 

Relative humidity describes 

the relation of the existing 

vapor pressure at a given 

temperature to the maximum 

vapor pressure at that 

temperature. Air at a given 

temperature can absorb 

vapor until its saturation 

(100%). The difference 

between the dry and wet bulb 

temperature is the relative 

humidity at that temperature. 

The following website 

http://home.fuse.net/clymer/w

ater/wet.html contains a 

function for calculating the 

relative humidity given the 

wet and dry bulb 

temperatures.
10

the humidity should be applied during the lethality treatment 

and before the drying step occurs. It is also recommended 

that establishments treat the lethality and drying steps as 

separate stages to ensure that lethality is achieved before 

the product dries out. This is why FSIS recommends that 

the desired product temperature be measured or verified 

prior to the drying stage. One way for an establishment to 

know that the product has not dried out before a lethal timetemperature combination is attained is to measure the water 

activity of the product after the lethality treatment but before 

drying. Some published articles (for example, Buege et al.,

2006a) may report the water activity at the point in the 

process for comparison. Another way is for the 

establishment to monitor the wet-bulb temperature early in 

the process, because it provides a good indication of product 

surface temperature, which strongly influences lethality 

(Buege, 2006). Further explanation and directions for 

making a wet-bulb thermometer are in Attachment 2. 

Some simple and practical measures that can be used to aid 

in meeting the humidity level utilized in the scientific support 

documents include: 

• Seal the oven: Close the smokehouse doors and 

oven dampers to provide a closed system and 

prevent moisture loss. 

• Add humidity: 

o Place one or more shallow, wide pans of hot 

water in the oven to increase the humidity in 

the system. Conduct a test run to determine 

whether the water evaporates. 

o Injecting steam or a fine water mist in the oven 

can also add humidity. 

In either case, the use of a humidity sensor or the use of 

wet-bulb and dry-bulb thermometers (to measure relative 

humidity) would enable the operator to determine whether 

adequate humidity is being applied. 

In order to ensure adequate humidity is attained, the

establishment should monitor the humidity throughout 

the lethality treatment. The process should be monitored 

using wet and dry bulb thermometers (used to determine 

relative humidity) or a humidity sensor. 

NOTE: A literature review has shown that at least 27-32% 

relative humidity should be present during the cooking 

process to ensure that adequate lethality is attained. In 

addition, the wet bulb temperature should reach at least 

KEY DEFINITIONS

The dry-bulb temperature 

refers to the ambient air 

temperature. It is called “drybulb” because the air 

temperature is indicated by a 

thermometer not affected by 

the moisture in the air or as a 

result, evaporative cooling. 

The dry-bulb temperature is 

most commonly measured by 

jerky-makers.

The wet-bulb temperature is 

the temperature indicated by a 

moistened thermometer bulb 

exposed to the air flow. A wetbulb thermometer measures 

the extent of cooling that 

happens as moisture dries from 

a surface, a process also 

known as evaporative cooling. 

The wet-bulb temperature is 

always lower than the dry-bulb 

temperature except when there 

is 100% relative humidity, when 

they will be identical. Because 

evaporative cooling occurs on 

the surface of thin jerky strips, 

the wet-bulb temperature is 

more accurate measurement of 

product surface temperature.

A Sealed oven is generally 

defined as one in which the 

smokehouse doors and 

smokehouse oven dampers are 

closed to prevent moisture 

loss. 
11

125-130°F for an hour or more during the lethality process (Buege, 2006a; Harper, 

2009). See page 16 for more information.

 

The following website http://home.fuse.net/clymer/water/wet.html contains a function for 

calculating the relative humidity given the wet and dry bulb temperatures. A basic wet 

bulb thermometer can be prepared by fitting a wet, moisture-wicking cloth around a dry 

bulb thermometer. To maintain a wet cloth during the process, submerse an end of the 

cloth in a water supply. The cloth must remain wet during the entire lethality treatment 

especially if smoke is applied. The establishment should inspect the wet-bulb sock prior 

to thermal processing and should be changed as necessary depending on the sock’s

condition. Attachment 2 contains more details for creating a wet-bulb thermometer. 

The use of a wet bulb thermometer is especially important for production at high 

altitudes or areas of low humidity. In fact, processing failures in the manufacture of

jerky have occurred in establishments located at high altitudes. Establishments located 

at higher altitudes will generally have a lower atmospheric pressure. This leads to lower 

boiling points and faster evaporation from the product surface, which can lead to 

undesirable evaporative cooling and drying of the product surface. Furthermore, at high 

altitudes, the relative humidity can be less at the higher altitude due to the lower air 

pressure (if the temperature at sea level and the high altitude is the same). As a result, 

at high altitudes, the amount of moisture added to the smokehouse chamber necessary 

to achieve a given log reduction of bacteria may need to be increased to account for 

lower levels of humidity in the ambient air. Adjustments to the amount of humidity added 

to the smokehouse chamber to account for changes in humidity in the ambient air at 

high altitudes will need to be made by establishments on a case-by-case basis as part 

of the initial design of the system to ensure that the humidity in the actual process 

matches the level in the scientific supporting documentation. 

Establishments should also take into account variability in relative humidity in the 

ambient air throughout different times of year. 

 Step 5 – Drying: 

Drying is the process during which water is removed from the product. After the lethality 

treatment, jerky is dried to meet a finished product water activity level that is sufficient

for food safety purposes. After drying is complete, the establishment should monitor or 

verify the water activity to demonstrate that the product has attained the critical limit for 

shelf-stability. It is important that the establishment achieves the water activity of the 

finished product identified in its supporting documentation. 

FSIS is aware that some manufacturers rely upon the maximum moisture protein ratio 

(MPR), rather than water activity, for determining whether their process adequately 

dries the jerky to produce a shelf-stable product. MPR is an inappropriate indicator of 

shelf-stability. Water activity (also referred to as aw), however, as measured by an 

instrument such as a water activity meter, is the more appropriate indicator to verify 

jerky is properly dried for food safety. This is because water activity is a better measure 

of available water (or water that is not bound by other components) for microbial growth 

than MPR. Minimizing available water (e.g., achieving a water activity of 0.85 or less) is 

critical for controlling growth of pathogens. However, an MPR of 0.75:1 or less remains 

part of the standard of identity for jerky (for labeling purposes only). Thus, an MPR of 
12

0.75:1 or less is necessary to label the product “jerky,” but it 

is not always sufficient to ensure safe jerky products. In 

addition, in order to label a product “jerky” it should be shelfstable. Although FSIS does not define jerky as shelf-stable 

in the regulatory standards of identity (9 CFR part 319), 

consumers consider and expect jerky to be shelf-stable. 

A water activity critical limit of 0.85 or lower should control 

growth of all bacterial pathogens of concern as well as mold

for products stored in an aerobic or oxygen containing 

environment such as in ambient air; however, if the product 

is vacuum packaged in an oxygen impervious packaging 

(creating an anaerobic environment where no oxygen is 

present), the water activity critical limit could be 0.91 or 

lower. These limits are based on the growth and toxin 

production limits for Staphylococcus aureus under optimal 

conditions with and without oxygen present (ICMSF, 1996). 

Establishments that choose to use these limits as support for 

the shelf-stability of their product may cite this guideline as 

supporting documentation for these limits and are not 

expected to provide additional scientific support.

NOTE: Vacuum packaged products with a water activity 

level > 0.85 and ≤ 0.91 should be kept refrigerated once the 

package is opened because the product would no longer be 

considered shelf-stable once it is exposed to oxygen. Lack 

of shelf-stability once the product is exposed to oxygen is 

mainly a concern for products that would not be consumed 

within a single serving as these products are not likely to be 

vacuum packaged by the consumer between servings. 

Therefore, unless the establishment has support that the 

product is likely to be consumed in a single serving, vacuum 

packaged products with a water activity in the range of > 

0.85 and ≤ 0.91 should be labeled with a statement such as 

“Refrigerate After Opening” (as described in 9 CFR 

317.2(k)). 

KEY DEFINITIONS

Shelf-stable is the condition 

achieved when meat and 

poultry products can be 

stored under ambient 

temperature and humidity 

conditions, and if the 

package integrity is 

maintained during storage, 

shipping, display at retail, 

and in the home, will not 

become unsafe throughout 

the manufacturer’s specified 

shelf-life. 

Water activity, also referred 

to as aw, is a measure of the 

concentration of moisture 

(i.e., water) and its 

availability in a food. The 

amount of water available in 

a food depends on the total 

concentration of all dissolved 

substances in the product 

because they bind water. 

Thus, if ingredients such as 

salt or sugar are added to 

food, they compete with the 

bacteria for available water. 

Moisture-protein-ratio

(MPR) expresses the percent 

moisture divided by the 

percent protein. MPR is 

commonly used in the U.S. to 

classify dried sausages and 

other meat products. 

Although MPR values 

indicate the degree of 

product drying, they are not 

necessarily indicative of 

microbial safety or product 

shelf-stability because they 

do not take into account 

availability of the water.

KEY QUESTION

Question: Should an establishment use the MPR to 

determine whether its process produces a shelf-stable 

product?

Answer: No. Establishments should use water activity to 

demonstrate that the product has attained the critical limit 

for shelf-stability. 
13

 Step 6 – Post-drying heat step: A post-drying heat step may be added to 

increase the level of pathogen reduction beyond that achieved by heating alone.

This step may be needed for processes that do not result in an adequate reduction of 

Salmonella through the initial heating process. Adding a post-drying heat step has the 

potential to reduce Salmonella levels by approximately 2 logs from the level of reduction 

achieved during initial heat step. One example of a post-drying heat step that has been 

found to reduce Salmonella levels by approximately 2 logs is to heat the dried product in 

a 275°F oven for 10 minutes (Harrison et al., 2001). 

 Step 7 – Handling: Product is often handled after the lethality and drying steps

and prior to/during packaging. 

Establishments should control their processes to prevent contamination of product with 

pathogens from product handling after the lethality and drying steps. Such controls 

should include ensuring that cross-contamination of product is minimized prior to 

packaging, and ensuring that the product is packaged in such a way that crosscontamination of product post-packaging is also minimized (e.g., with a good seal to

maintain package integrity throughout storage, shipment and display). 

Cross-contamination of product can occur from situations such as the following: 

• Use of the same equipment (e.g., grinders, mixers, or packaging equipment) for 

both raw and cooked products without complete cleaning and sanitizing of the 

equipment between production lots. 

• Placing cooked product on the same surface (e.g., cutting table) as raw product 

without complete cleaning and sanitizing of the surface before reuse. 

• Using the same utensils or containers (e.g., scoops or buckets) for both raw and 

cooked product without complete cleaning and sanitizing of the surface before 

reuse. 

• Condensation, aerosolization, or dusting of dry ingredients into the processing 

environment. 

The establishment is required to maintain sanitation in the ready-to-eat (RTE) area to 

ensure that food contact surfaces are free of contamination from Lm and other 

pathogens, such as Salmonella, in accordance with 9 CFR part 430. The establishment

is also required to develop and implement Sanitation SOPs (9 CFR 416) to ensure that 

contamination and adulteration of the product is prevented after the lethality treatment. 

Further guidance on post-processing handling and sanitation for ready-to-eat products 

including jerky can be found in the Salmonella Compliance Guidelines for Small and 

Very Small Meat and Poultry Establishments that Produce Ready-to-Eat (RTE) 

Products and the Compliance Guidelines to Control Listeria monocytogenes in PostLethality Exposed Ready-to-Eat Meat and Poultry Products. 
14

Scientific Support Documents Available for Jerky Processing

Establishments have numerous options for the types of scientific documents that can 

be used to support that the process achieves adequate lethality. Examples of the 

scientific support documents available to help develop a safe jerky process and 

product are discussed below along with considerations for each type of support. 

Product sampling results, based on historical data alone, should not be used as 

scientific support for a jerky process because they do not provide information on the 

level of pathogen reduction that is achieved for the process. 

Compliance Guidelines

FSIS has issued a number of different compliance guidelines that have application to 

jerky processing. It is important to note that, while FSIS considers these documents to 

be guidelines, if followed precisely they are considered as validated process schedules 

because the guidelines contain processing methods already accepted by the Agency as 

effective in safely cooking meat and poultry products. 

Some considerations for each of these compliance guidelines are outlined below.

 FSIS Appendix A: Compliance Guidelines For Meeting Lethality 

Performance Standards For Certain Meat and Poultry Products 

For meat jerky, use of the time-temperature combinations provided in Appendix A,

including those temperatures above 158°F in which the desired lethality is 

instantaneous, should help to ensure the safety of the product. These time-temperature 

combinations are based on experiments that were done with products without added 

salt or sugar. Added salt, sugar, or other substances that reduce water activity will 

increase the heat resistance of bacteria in a product. However, time and experience 

have shown that the time-temperature combinations in the lethality compliance 

guidelines have been sufficient to produce safe products even with both salt and sugar 

added, but the humidity during heating is a critical factor. The humidity options in

the Appendix A guidelines that are applicable to jerky processing are as follows:

o Heating roasts of any size to a minimum internal temperature of 145 °F (62.8 

°C) in an oven maintained at any temperature if the relative humidity of the 

oven is maintained either by continuously introducing steam for 50 percent of 

the cooking time or by use of a sealed oven for over 50 percent of the cooking 

time, or if the relative humidity of the oven is maintained at 90 percent or 

above for at least 25 percent of the total cooking time, but in no case less 

than 1 hour; or

o Heating roasts of any size in an oven maintained at any temperature that will 

satisfy the internal temperature and time combinations [from the chart

provided in Appendix A] if the relative humidity of the oven is maintained at 90 

percent or above for at least 25 percent of the total cooking time, but in no 

case less than 1 hour. The relative humidity may be achieved by use of steam 

injection or sealed ovens capable of producing and maintaining the required 

relative humidity.
15

NOTE: The “continuously introducing steam” option 

is meant to refer to the use of live steam although it 

may also apply to establishments that spray water 

onto hot heating elements which creates steam that 

in turn produces humidity in the smokehouse. 

“Continuous” does not mean that the steam is 

injected for at least one hour during one stage; rather, 

steam could be injected during stages or time 

intervals during the lethality as long as the total 

amount of time the steam is introduced for adds up to 

over 50% of the cooking time. 

It is FSIS’s expectation that establishments using any 

of the options in the Appendix A guidelines as their 

supporting documentation will maintain the humidity 

level in the oven for at least the percentage of 

cooking time specified by the method, but in no case 

less than one hour. It is critical that humidity is 

maintained during cooking to ensure a safe product. 

Guidance for maintaining humidity is provided here. 

In addition, prudent establishments using any of the 

options in the Appendix A guidelines will either: 1) 

monitor the humidity level of their ovens (e.g., by use 

of dry and wet bulb thermometers to calculate the 

relative humidity or use of a humidity sensor that 

provides a direct measurement), or 2) provide 

documentation that supports that, when the oven 

dampers are closed, humidity is maintained in the 

ovens, or that supports that steam is being 

continuously injected. 

Moreover, it is also expected that establishments 

using the sealed oven method will have a procedure 

for checking that the dampers are properly working. 

This procedure could include a review of records from 

a computerized system that contains documentation

of the time at which the oven dampers were open and 

were closed, along with a maintenance program to 

periodically monitor that the seals are intact and 

functional, and that when the oven dampers are 

closed, a tight seal is obtained that prevents a

significant loss of humidity. Establishments should 

Key Considerations for 

Options in the Appendix A 

guidelines that utilize < 90%

humidity

Establishments have the 

flexibility to use the options in 

Appendix A that utilize less than

90% relative humidity; that is, 

the options of: Heating roasts of 

any size to a minimum internal 

temperature of 145°F (62.8°C) in 

an oven maintained at any 

temperature if the relative 

humidity of the oven is 

maintained either by 

continuously introducing steam 

for 50 percent of the cooking 

time or by use of a sealed oven 

for over 50 percent of the 

cooking time, or if the relative 

humidity of the oven is 

maintained at 90 percent or 

above for at least 25 percent of 

the total cooking time, but in no 

case less than 1 hour.

If an establishment can not 

apply these humidity options 

for equal to or more than one 

hour, then the humidity of the 

oven should be maintained at 

90% or above throughout the 

lethality treatment. 

If an establishment chooses to 

use one of the options that 

require less than 90% relative 

humidity, then only those 

time/temperature combinations 

of equal to or greater than 145°F 

for 4 minutes apply. This option 

is included in the Appendix A

guidelines but is often 

overlooked. It is also important 

to note again that the 

temperature values in the 

Appendix A correspond to 

product temperatures, not oven 

temperatures. 

It is important that establishments maintain and monitor 

the humidity levels in the oven.
16

also consider whether there are other openings, particularly in older smokehouses, such 

as drain valves or air intake valves; that need to be closed in order to ensure a seal is 

obtained. Finally, some older ovens may have a stack or other opening that can’t be 

closed. For those establishments with older ovens that can not be completely closed, 

the sealed oven method should not be used. However, the establishment may choose 

to close what they are able and to add moisture in the system either by continuously 

introducing steam or another validated method. 

Establishments using the option to continuously inject steam should also have a 

procedure or mechanism in place to ensure that steam is in fact being continuously 

injected. Such a mechanism could include the monitoring of the time that steam is

continuously introduced into the oven during the cooking time or use of temperature 

charts, with wet and dry bulb temperatures, that show that the wet bulb temperature is 

rising for 50% of the cooking time based upon a letter from the manufacturer stating that 

when the relative humidity is rising it is because of live steam injection. 

FSIS recommends that establishments monitor the 

humidity levels in the oven even when using one of 

the options that requires < 90% humidity because the 

literature suggests that at least 27-32% relative 

humidity should be present during the cooking 

process to ensure that adequate lethality is attained. 

In addition, the literature suggests that the wet bulb 

temperature should reach at least 125-130°F for an 

hour or more during the lethality process. Wet bulb 

temperature is generally a strong indicator of product 

internal temperature early in the process. Therefore, 

maintaining the wet bulb at a high enough level to 

cause lethality (125-130°F) is recommended (Buege, 

2006a; Harper, 2009), although achieving a specified 

relative humidity or wet bulb is not a requirement for all of the humidity options in the 

Appendix A guidelines. Finally, although FSIS recommends that establishments monitor 

the humidity levels in the oven or provide documentation that supports that the oven is 

sealed, or steam is continuously injected for each batch or lot produced, the 

establishment is required to list the procedures and the monitoring frequency chosen for 

each CCP (9 CFR 417.2(c)(4)). 

NOTE: Establishments that choose a monitoring frequency less than each batch or lot 

should consider how they will support product safety in the event of a deviation if 

documentation is not available to support that batches or lots of product produced since 

the last monitoring were processed with adequate humidity.

 FSIS Guidance on Safe Cooking of Non-Intact Meat Chops, Roasts, and 

Steaks for time/temperature combinations

For meat jerky, the use of the time-temperature combinations provided in the FSIS 

guidance on the safe cooking of non-intact meat chops, roasts, and steaks should also 

help to ensure the safety of the product. Humidity should also be considered when 

using this time/temperature table; therefore, the same options for humidity in Appendix 

A should also be used with this guidance. In addition, the same expectations regarding 

The humidity parameters in the 

Appendix A guidelines cannot 

be maintained in a home-style 

dehydrator. However, 

processes that can achieve an 

adequate reduction of 

Salmonella and E. coli 

O157:H7 in dehydrators are 

described in the studies by 

Buege et al. (2006), and 

Harrison et al. (2006). 
17

maintaining and monitoring humidity for Appendix A apply for establishments that use 

the FSIS Guidance on Safe Cooking of Non-Intact Meat Chops, Roasts, and Steaks for 

time/temperature combinations.

 Time-Temperature Tables For Cooking Ready-To-Eat Poultry Products

For poultry jerky, to produce a safe product, establishments can use the minimum 

internal temperatures listed in Appendix A of 160°F for uncured poultry or 155°F for 

cured and smoked poultry. 

NOTE: If highly pathogenic avian influenza (HPAI) virus H5N1 is identified as a 

hazard reasonably likely to occur, cured and smoked poultry should be cooked to 

at least 158°F or a time and temperature combination that achieves a 7-log10 

reduction of Salmonella. 

The required reduction of Salmonella can also be achieved by using one of the timetemperature combinations listed in the Time-Temperature Tables for Cooking Ready-toEat Poultry Products. Regardless of whether Appendix A or the Time-Temperature 

tables are used, humidity during heating is a critical 

factor. As with meat jerky, the time-temperature 

combinations would be sufficient to produce safe 

products with both salt and sugar additives if the 

processor uses the humidity parameters applicable to 

beef as described in Appendix A. The same 

expectations regarding maintaining and monitoring 

humidity for Appendix A apply for establishments that 

use the Time-Temperature Tables for Cooking Readyto-Eat Poultry Products.

Journal articles

Journal articles are a primary type of support used for 

jerky processes as a number of studies have been 

conducted to determine time/temperature/humidity 

combinations that result in adequate lethality for jerky. 

Attachment 1 contains a summary of 

time/temperature/humidity combinations, along with 

other critical operational parameters from published 

studies that have been found to result in adequate 

lethality. 

If an establishment chooses to utilize a journal article as 

scientific support, it should ensure that the critical 

operational parameters used in the study match those 

used in the actual process. If one or more of the 

parameters are not addressed or do not match the level 

used in the support, then the establishment’s process 

may not achieve the same level of lethality as cited in 

the journal article. In that case, the establishment 

Key Considerations for 

Journal Articles in 

Attachment 1

Attachment 1 contains a 

summary of published studies 

that have been found to 

achieve adequate lethality for 

jerky and the critical 

operational parameters. The 

Attachment is provided to help 

establishments identify 

alternatives to the Appendix A

guidelines. 

This Attachment is not 

considered adequate support 

on its own because it does not 

provide the details of each 

study that an establishment 

needs to determine if the study 

is representative of the actual 

process. 

For this reason, if an 

establishment chooses to use 

one of the articles provided in 

Attachment 1, FSIS expects 

that the establishment will 

have a full copy of the original 

article on file.
18

KEY QUESTION

Question: Can an establishment’s process use a different level of a critical 

operational parameter (for example, a higher concentration of an antimicrobial 

or a higher processing temperature) than what was used in the support 

document? 

Answer: Generally, establishments should use the same critical operational 

parameters as those in the support documents. In some circumstances, 

establishments may be able to support using critical operational parameters that 

are different from those in the support documents (e.g., higher concentrations of 

antimicrobials or higher thermal processing temperatures). In these cases, 

establishments should provide justification supporting that the levels chosen are 

at least as effective as those in the support documents. This justification is 

needed because higher levels of a critical operational parameter may not always 

be equally effective. For example, antimicrobial agents may only be effective 

within a range of concentrations, after which point efficacy may decrease. 

Similarly, higher processing temperatures may result in the surface of the 

product drying out before adequate lethality is achieved. In addition to ensuring 

that the levels chosen are at least equally as effective as those in the support 

documents, establishments should ensure the levels are also safe and suitable 

(http://www.fsis.usda.gov/OPPDE/rdad/FSISDirectives/7120.1.pdf). 

should document a justification as to why that parameter does not need to be met or 

measured or why it differs from the support. The establishment should consider 

whether it is using the same: 

• Product (e.g., species, type-whole muscle or ground)

• Product formulation

• Product time/temperature combination

• Relative humidity at each stage (including, if reported, using the same humidity 

levels at the beginning and end of each stage)

• Type or pH of marination (if applicable)

• Smoke (if applicable)

as used in the article. The establishment should also ensure that the composition of the 

product (% salt, % fat) used in the study is the same as the composition of the actual 

product being produced. A prudent establishment should have knowledge of the 

products it produces. Because meeting the critical operational parameters is essential 

to achieving lethality in the product, the parameters used or measured in the article 

should be addressed in the process. 
19

Challenge Studies

In cases where an establishment’s process does not match available scientific support 

documents, such as a Compliance Guideline or published journal article, establishments 

may decide to conduct an inoculation challenge study to support that their processes 

achieve adequate lethality (e.g., for poultry jerky at least a 7.0 log reduction of 

Salmonella spp. and for meat jerky at least a 5.0 log reduction of Salmonella spp. and at 

least a 5.0 log reduction for E. coli O157:H7 for products containing beef as well as

sufficient reduction for Lm). The challenge study should be designed to closely match 

the critical operational parameters in the establishment’s actual process. In addition, it 

is important that the challenge study is conducted using the pathogen of interest, and 

that the inoculation level is sufficient to show adequate log reduction of the target 

pathogens. 

Challenge studies conducted using pathogens such as Salmonella spp. and E. coli

O157:H7 should be conducted in a testing laboratory and not in the processing plant 

environment. FSIS considers all Salmonella and E. coli O157:H7 serotypes to be 

pathogens of public health concern. If an establishment chooses to conduct a 

challenge study in a plant environment, to best represent actual processing conditions 

for example, then the establishment should choose surrogate organisms that have been 

found to respond similarly to the pathogens of interest (e.g., Salmonella and if 

applicable, E. coli O157:H7). For example, the University of Wisconsin has conducted 

research with ground-and-formed jerky and found that two Pediococcus strains (Saga 

200 and Biosource) have similar heat-resistance to Salmonella and can be used in inplant validation studies (Borowski et al., 2009). FSIS has identified four surrogate 

organisms that have been shown to respond similarly to E. coli O157:H7 during cooking 

(see the following askFSIS Q&A for more information) for use in in-plant validation 

studies. 

Challenge studies should be equivalent to peer-reviewed scientific literature. All of the 

critical elements previously listed for a study above need to be included to permit 

evaluation or confirmation of the results. For more information on conducting challenge 

studies please review the article published by the National Advisory Committee on 

Microbiological Criteria for Foods in the Journal of Food Protection in 2010. 

At a minimum, a study for a microbiological food safety hazard should identify: 

• The hazard (biological, physical, and chemical), 

• The expected level of hazard reduction or prevention to be achieved, 

• The processing steps that will achieve the specified reduction or prevention, 

• All critical operational parameters or conditions (e.g., time, temperature, and 

humidity) necessary to achieve the reduction, 

• How these processing steps/parameters can be monitored, 

• The critical ingredients (e.g., salt, sugar, and cure), and

• The critical product characteristics (e.g., pH, water activity, and fat content). 
20

References 

Borowski, A.G., Ingham, S.C., Ingham, B.H. 2009. Validation of ground-and-formed 

beef jerky processes using commercial lactic acid bacteria starter cultures as pathogen 

surrogates. J. Food Prot. 72(6): 1234-1247.

Buege, D. R., Searls, G. Ingham, S.C. 2006a. Lethality of commercial whole-muscle 

beef jerky manufacturing processes against Salmonella serovars and Escherichia coli 

O157:H7. J. Food Prot. 69(9): 2091-2099. 

Buege, D.R., Searls, G., Mohanan, S., Buege, D.R. 2006b. Survival of Staphylococcus 

aureus and Listeria monocytogenes on vacuum-packaged beef jerky and related 

products stored at 21°C. J. Food Prot. 69(9) 2263-2267.

Calicioglu, M., Sofos, J.N., Samelis, J., Kendall, P.A., Smith, G.C. 2002. Destruction of 

acid-adapted and non-adapted Salmonella during drying and storage of beef jerky 

treated with marinade. Animal Sciences Research Report. Colorado State University. 

Calicioglu, M., Sofos, J.N., Samelis, J., Kendall, P.A., Smith, G.C. 2003. Effects of acid 

adaptation and modified marinades on survival of postdrying Salmonella contamination 

on beef jerky during storage. J. Food Prot. 66(3):396-402. 

Eidson, M., Sewell, C. M., Graves, G, Olson, R. 2000. Beef jerky gastroenteritis 

outbreaks. Environ. Health. 62:9-13. 

Faith, N.G., Le-Coutour, N.S., Alvarenga, M.B., Calicioglu, M., Buege, D.R., Luchansky, 

and J. B. 1998. Viability of Escherichia coli O157:H7 in ground and formed beef jerky 

prepared at levels of 5 and 20% fat and dried at 52, 57, 63, or 68 degrees C in a homestyle dehydrator. Int. J. Food Microbiol. 41(3):213-221. 

Getty, K.J.K., Boyle, E.A.E., Roberts, M.N., Lonneker, S.M. 2006. Jerky Validation for 

Small and Very Small meat and Poultry Businesses: Final Report. Available at: 

http://www.fsis.usda.gov/PDF/C-12_New_Technology_FY2004_Final_Report.pdf. 

Accessed 25 January 2012. Note: the full study for this report can be found in the 

Harper et al. (2009) reference below. 

Goepfert, J.M., Iskander, I.K., Amundson, C.H. 1970. Relation of the heat resistance of 

Salmonellae to the water activity of the environment. Appl. Microbiol. 19(3):429-33. 

Goodfellow, S.J., Brown, W.L.. 1978. Fate of Salmonella inoculated into beef for 

cooking. J. Food Prot. 41(8):598-605. 

Harper, N.M., Roberts, M.N., Getty, K.J.K., Boyle, E.A.E., Fung, D.Y.C., Higgins, J.J. 

2009. Evaluation of two thermal processing schedules at low relative humidity for 

elimination of Escherichia coli O157:H7 and Salmonella Serovars in chopped and 

formed beef jerky. J. Food Prot. 72: 2476-2482.
21

Harrison, J.A. Harrison, M.A. 1996. Fate of Escherichia coli O157:H7, Listeria 

monocytogenes, and Salmonella Typhimurium during preparation and storage of beef 

jerky. J. Food Prot. 59(12):1336-8. 

Harrison, J.A. Harrison, M.A., Rose-Morrow, R.A., Shewfelt, R.L. 2001. Home-style 

beef jerky: effect of four preparation methods on consumer acceptability and pathogen 

inactivation. J. Food Prot. 64(8):1194-98. 

Harrison, M. A., Singh, R.K., Harrison, J.A., Singh, N. 2006. Antimicrobial intervention 

and process validation in beef jerky processing. Final Report. Available at: 

http://www.fsis.usda.gov/PDF/C-17_New_Technology_FY2004_Final_Report.pdf. 

Accessed 25 July 2011. 

International Commission on Microbiological Specifications for Foods (ICMSF). 1996. 

Microorganisms in Foods 5: Characteristics of Microbial Pathogens. London: Blackie 

Academic & Professional. 524 p. 

National Advisory Committee on Microbiological Criteria for Foods. 2010. Parameters 

for determining inoculated pack/challenge study protocols. J. Food Prot. 73(1): 140-

202. 

Porto-Fett, A.C.S., Call, J.E., Luchansky, J.B. 2008. Validation of a commercial 

process for inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, and 

Listeria monocytogenes on the surface of whole muscle beef jerky. J. Food Prot. 71(5): 

918-926.

Swayne, D. E. and Beck, J.R. 2005. Experimental study to determine if lowpathogenicity and high-pathogenicity avian influenza viruses can be present in chicken 

breast and thigh meat following intranasal virus inoculation. Avian. Dis. 49:81-85. 

Thomas, C. and Swayne, D.E. 2007. Thermal inactivation of H5N1 high pathogenicity 

avian influenza virus in naturally infected chicken meat. J. Food Prot. 70(3):674-680. 

Helpful Web Resources

Dry Bulb, Wet Bulb, and Dew Point Temperature

Background on 2003 Salmonella Kiambu jerky outbreak

Compliance Guidelines to Control Listeria monocytogenes in Post-Lethality Exposed 

Ready-to-Eat Meat and Poultry Products

Food Safety Regulatory Essentials (FSRE) Processing Procedures: Dried Meats

FSIS Appendix A: Compliance Guidelines For Meeting Lethality Performance Standards 

For Certain Meat and Poultry Products

FSIS Guidance on Safe Cooking of Non-Intact Meat Chops, Roasts, and Steaks for 

time/temperature combinations
22

Making Your Own Wet Bulb Thermometer

Salmonella Compliance Guidelines for Small and Very Small Meat and Poultry 

Establishments that Produce Ready-to-Eat (RTE) Products

Time-Temperature Tables For Cooking Ready-To-Eat Poultry Products
This Attachment is not considered adequate support on its own because it does not provide the details of each study an 

establishment needs to determine if the study is representative of the actual process.

23

Attachment 1: Time, temperature, and humidity combinations reported in the literature for beef jerky that achieve at 

least a 5 log reduction in E. coli O157:H7. NOTE: All processes reported in this Attachment achieved at least a 5 log 

reduction of Salmonella in addition to E. coli O157:H7. 

Reference Product Marinated

(Yes/No)

Smoke

Added

(Yes/No)

Oven Temperature

(°F)

Time

(min)

Humidity 

(%)

Log Reduction

(E. coli O157:H7)

Buege et al.

(2006a) 2

Whole 

muscle 

beef jerky

Yes – pH 

5.3

No Type 1-A* 

Stage 1 – 

145

170

Stage 2 – 

Choose either:

Dry-bulb at 170 and 

wet-bulb at 125

OR Dry-bulb at 170 

and wet-bulb at 130

OR Dry-bulb at 170 

and wet-bulb at 135

OR Dry-bulb at 170 

and wet-bulb at 140 

for at least

Stage 3- 

Dry at 170 dry-bulb

15 

15 

at least 60

at least 60 

at least 30 

10 

to targeted 

doneness

27

32

37

43

≥5 

 

2

 Buege, D.R., Searls, G., and Ingham, S.C. 2006a. Lethality of commercial whole-muscle beef jerky manufacturing processes against Salmonella 

Serovars and Escherichia coli O157:H7.
This Attachment is not considered adequate support on its own because it does not provide the details of each study an 

establishment needs to determine if the study is representative of the actual process.

24

Reference Product Marinated

(Yes/No)

Smoke

Added

(Yes/No)

Oven Temperature

(°F)

Time

(min)

Humidity (%) Log Reduction

(E. coli O157:H7)

Buege et al.

(2006a) 

Whole 

muscle 

beef jerky

Yes – pH 

5.3

No Type 1-B*

Stage 1 – 

145

Then choose either:

Stage 2 – 

Dry-bulb at 150

THEN dry bulb at 150 

and wet bulb at 130; 

THEN dry bulb at 150

OR

Stage 2- 

Dry-bulb at 190

THEN dry bulb at 190 

and wet bulb at 130; 

THEN dry bulb at 190

15 

15 

60 

to targeted 

doneness

15 

60 

to targeted 

doneness

56

19

≥5 

Whole 

muscle 

beef jerky

Y – pH 5.3 No Type 2**

145

170

15 

to targeted 

doneness

27-31(start)***

17-21(end)

≥5 
This Attachment is not considered adequate support on its own because it does not provide the details of each study an 

establishment needs to determine if the study is representative of the actual process.

25

Reference Product Marinated

(Yes/No)

Smoke

Added

(Yes/No)

Oven Temperature

(°F)

Time

(min)

Humidity (%) Log Reduction

(E. coli O157:H7)

Buege et al.

(2006a) 

Whole 

muscle 

beef jerky

Yes – pH 

5.3

No Type 3**

145

170

90 

to targeted 

doneness

41(start)***

21(end)

≥5 

Whole 

muscle 

beef jerky

Yes – pH 

5.3

No Type 5**

180 to targeted 

doneness

29(start)****

15(end)

≥5† 

*Type 1-A and Type 1-B processes with a higher dry-bulb temperature in Stage 1, a higher wet-bulb temperature or longer time 

in Stage 2, or a higher dry-bulb temperature in Stage 3, as long as other parts of the process are not changed, can also be 

considered validated because they should have greater lethality.

**Processes reaching higher dry-bulb temperatures in either stage can also be considered validated because they would have 

greater lethality.

***Humidity values are from Table 3 in Buege et al. (2006a). 

 Humidity values are from Table 5 in Buege et al. (2006a).

Oven: Pans of water were placed on the lowest rack in the smokehouse, and a low fan speed was used. Humidity 

(steam or water) was introduced in Type 1-A and 1-B processes. Study did not indicate whether dampers were open or 

closed. 

† Finished product water activity level was ≤ 0.85
This Attachment is not considered adequate support on its own because it does not provide the details of each study an 

establishment needs to determine if the study is representative of the actual process.

26

** Processes reaching higher dry-bulb temperatures in either stage can also be considered validated because they would have 

greater lethality.

***Humidity values are from Table 3 in Buege et al. (2006a).

Oven: Pans of water were placed on the lowest rack in the smokehouse, and a low fan speed was used. Humidity 

(steam or water) was introduced in Type 1-A and 1-B processes. Study did not indicate whether dampers were open or 

closed.

Reference Product Marinated

(Yes/No)

Smoke

Added

(Yes/No)

Oven 

Temperature

(°F)

Time

(min) 

Humidity % 

(%) 

Log Reduction

(E. coli O157:H7) 

Buege et al.

(2006a) 

Whole 

muscle beef 

jerky 

Yes – pH 

5.3

No Type 7**

120

130

140

170

60 

60 

60 

60 

43***

15

≥5 
This Attachment is not considered adequate support on its own because it does not provide the details of each study an 

establishment needs to determine if the study is representative of the actual process.

27

*Oven temperatures are average of continuous readings taken every 30s after CUT.

Oven: Dampers were completely open. 

 

†

Finished product water activity levels were ≤ 0.85

 

3 Porto-Fett, A.C.S., Call, J.E., and Luchansky, J.B. 2008. Validation of a commercial process for inactivation of Escherichia coli O157:H7, Salmonella

Typhimurium, and Listeria monocytogenes on the surface of whole muscle beef jerky. Journal of Food Protection. 71(5): 918-926.

Reference Product Marinated

(Yes/No)

Smoke

Added

(Yes/No)

Oven/Product

Temperature

(°F)*

Time

(hours)

Humidity 

(%)

(Start/End)

Log Reduction

(cfu/strip)

(E. coli O157:H7)

Porto-Fett et 

al. (2008)3

Whole 

muscle beef 

jerky 

Yes – ~pH 

5.5

Yes 178 1.5 63.4

21.9

≥7

Whole 

muscle beef 

jerky 

No Yes 178 1.5 63.4

21.9

≥7

Whole 

muscle beef 

jerky 

Yes – ~pH 

5.5

Yes 178.3 2.5 63.8

21.5

≥7†

Whole 

muscle beef 

jerky 

No Yes 178.3 2.5 63.8

21.5

≥7

Whole 

muscle beef 

jerky 

Yes – ~pH 

5.5

Yes 178.5 3.5 62.3

19.2

≥7†

Whole 

muscle beef 

jerky

No Yes 178.5 3.5 62.3

19.2

≥7†
This Attachment is not considered adequate support on its own because it does not provide the details of each study an 

establishment needs to determine if the study is representative of the actual process.

28

*Humidity levels were calculated from actual dry and wet-bulb temperatures reported in Getty et al. (2006):

http://www.fsis.usda.gov/PDF/C-12_New_Technology_FY2004_Final_Report.pdf. Although the report states that humidity 

remained at less than 10% throughout the entire smokehouse cycle, humidity levels calculated from dry and wet-bulb 

temperatures in the report were higher, as indicated in the table. This was verified through personal communication with the 

author [April 2011]. 

Oven: Automated dampers and steam injection.

 

†

Finished product water activity level was ≤ 0.85

 

4 Harper, N.M., Roberts, M.N., Getty, K.J.K., Boyle, E.A.E., Fung, D.Y.C., Higgins, J.J. 2009. Evaluation of two thermal processing schedules at low relative humidity 

for elimination of Escherichia coli O157:H7 and Salmonella Serovars in chopped and formed beef jerky. Journal of Food Protection. 72: 2476-2482. 5 Getty, K.J.K., Boyle, E.A.E., Roberts, M.N., Lonneker, S.M. 2006. Jerky Validation for Small and Very Small meat and Poultry Businesses: Final Report. Available 

at: http://www.fsis.usda.gov/PDF/C-12_New_Technology_FY2004_Final_Report.pdf. Accessed 25 January 2012. 

Reference Product Marinated

(Yes/No)

Smoke

Added

(Yes/No)

Oven 

Temperature

(°F)

Time

(min)

Humidity 

(%)* 

Log Reduction

(E. coli O157:H7)

Harper et al.

(2009),

4 Getty 

et al. (2006)5

Chopped 

and formed 

beef jerky 

No No

(smoke 

flavor was 

added)

Stage 0 –

Stage 1 – 132

Stage 2 – 132

Stage 3 – 132 

Stage 4 – 172

Stage 5 – 172 

Stage 6 – 172

Stage 7 – 172

Stage 8 – 172

Stage 9 – 172

Stage 10 – 172

Stage 11 – 172

Stage 12 – 172

14

16

14

16

14

16

14

16

14

16

14

5 h

32.6

52

14.5

22

22

22

22

22

22

22

22

22

≥5†
This Attachment is not considered adequate support on its own because it does not provide the details of each study an 

establishment needs to determine if the study is representative of the actual process.

29

*A spice rub mix was used. Two types of spice mixes (Colorado and BBQ) were used in the study. Results for one type of spice 

mix (Colorado) are reported here. Variability in lethality was found due to spice mix type. See Borowski et al. (2009) for details 

on the spice mixes used including pH and aw values and results for products prepared with the BBQ spice mix. 

**%RH values are approximate based on an average of the range of actual dry and wet bulb temperatures provided in the article. 

RH values reported as ND were not determined.

NOTE: All processes reported here used a commercial oven-smokehouse.

Oven: Dampers were open for processes without smoke added. 

†

Finished product water activity levels were ≤ 0.85

 

6 Borowski, A.G., Ingham, S.C., Ingham, B.H. 2009. Validation of ground-and-formed beef jerky processes using commercial lactic acid bacteria starter cultures as 

pathogen surrogates. Journal of Food Protection. 72(6): 1234-1247.

Reference Product Marinated

(Yes/No)

Smoke

Added

(Yes/No)

Oven 

Temperature

(°F)

Time

(min)

Humidity 

(%)**

Log Reduction

(E. coli O157:H7)

Borowski et al.

(2009)6

Ground-andformed beef 

jerky 

No*

No 

No

No

Type 2-A

170

130

170

30

120

90

57

22

28

7.35†

Ground-andformed beef 

jerky 

No*

No 

No

No

Type 3-A

170

170

170

30

15

130

7 

23

ND

6.8†

Ground-andformed beef 

jerky 

No*

No 

No

Type 4-A

135

185

90

150

67

9 

8.11†
This Attachment is not considered adequate support on its own because it does not provide the details of each study an 

establishment needs to determine if the study is representative of the actual process.

30

**A spice rub mix was used. Two types of spice mixes (Colorado and BBQ) were used in the study. Results for one type of 

spice mix (Colorado) are reported here. Variability in lethality was found due to spice mix type. See Borowski et al. (2009) for 

details on the spice mixes used including pH and aw values and results for products prepared with the BBQ spice mix.

**%RH values are approximate based on an average of the range of actual dry and wet bulb temperatures provided in the article. 

RH values reported as ND were not determined.

NOTE: All processes reported here used a commercial oven-smokehouse.

Oven: Dampers were open until smoke was added at which point dampers were closed. 

 

7 Smoke added after 30 min.

8 Smoke discontinued after 90 min.

Reference Product Marinated

(Yes/No)

Smoke

Added

(Yes/No)

Temperature

(°F) 

Time

(min)

Humidity 

(%)**

Log Reduction

(E. coli O157:H7)

Borowski et al.

(2009)

Ground-andformed beef 

jerky 

No*

Yes

Yes 

Yes 

Type 2-B

170

130

170

30

120

90

32

ND

ND

7.42

Ground-andformed beef 

jerky 

No*

No

No

Yes 

Type 3-B

170

170

170

30

15

130

7 

39

ND

7.41

Ground-andformed beef 

jerky 

No*

Yes7

Yes8

Type 4-B

135

185

90

150

68

ND

7.46
This Attachment is not considered adequate support on its own because it does not provide the details of each study an 

establishment needs to determine if the study is representative of the actual process.

31

NOTE: The process reported here used a commercial oven-smokehouse.

Oven: No humidity control. Study did not indicate whether dampers were open or not.

†

Finished product water activity level was ≤ 0.85

 

9 Harrison, M. A., R. K. Singh, J. A. Harrison and N. Singh. 2006. Antimicrobial intervention and process validation in beef jerky processing. Final Report. Available 

at: http://www.fsis.usda.gov/PDF/C-17_New_Technology_FY2004_Final_Report.pdf. Accessed 25 July 2011. 

Reference Product Marinated

(Yes/No)

Smoke

Added

(Yes/No)

Oven 

Temperature

(°F)

Time

(hours) 

Humidity 

(%) 

Log Reduction

(E. coli O157:H7)

Harrison et al.

(2006)9

Beef jerky 

strips

Yes No 143.6 8-9 33 >6†
32

Attachment 2: Making Your Own Wet Bulb Thermometer 

(Reprinted with permission)

By G. Burnham, S.C. Ingham and B.H. Ingham 

University of Wisconsin-Madison Center for Meat Process Validation 

If you are smoking or drying meat, there are several parameters to monitor which will 

help you control your process: dry bulb temperature, wet bulb temperature, and 

relative humidity. Research at the University of Wisconsin Center for Meat Process 

Validation has shown that monitoring wet bulb temperature is even more important 

(and much easier!) than monitoring product temperature during your process. Since 

wet bulb temperature is critical to process monitoring, this document describes how to 

easily, and perhaps inexpensively, construct a wet bulb thermometer. 

Dry bulb temperature, usually referred to as air temperature, is the smokehouse/oven 

property that is most commonly measured by jerky-makers. When people refer to the 

temperature (heat content) of the air, they are normally referring to the dry bulb 

temperature. It is called "dry bulb" because the air temperature is indicated by a 

thermometer that is not moistened and will not be affected by evaporative cooling. 

Wet bulb temperature is the temperature indicated by a moistened thermometer bulb 

exposed to air. A wet bulb thermometer measures the extent of cooling that happens as 

moisture dries from a surface (evaporative cooling). The wet bulb temperature is always 

lower than the dry bulb temperature except when there is 100% relative humidity. 

Because evaporative cooling occurs on the surface of thin jerky strips, the wet 

bulb temperature is more accurate measurement of product temperature. 

We developed a wet bulb thermometer (WBT) which is easy to assemble and 

economical for a meat processor to use. 

To begin assembling a wet bulb thermometer, you will need to determine what type of 

temperature measuring device you will use. You will need to use a temperature 

recorder with a “tip reading” probe/wire/stem. Either an instant read or a data-logging 

temperature measuring device will work; both are pictured in image 1. 

A - 3 styles of ‘instant read’ tempA 

B 

1 

erature measuring device

B - a data logger-style of temperature measuring device

In each case, the ‘tip reading’

probe/wire is circled.

Instant read temperature recorders.

(A) An instant read temperature

Recorder will offer immediate 

feedback, with the temperature 

displayed on the front of the unit. 

However, data may not be recorded 

with this type of unit; the processor 

must record the data periodically. 

See page 34 for more information 

on ordering instant-read 

temperature recorders.
33

A data logger-style temperature recorder. (B) This type of device keeps track of, or 

‘logs’ temperature over a period of time. An inexpensive data logger usually does not 

offer immediate readout of data. A processor must connect the data logger to a 

computer to view the temperature data. A data logger does, however, offer a continuous 

record of temperature history which can be important for HACCP documentation. See 

page 34 for information on ordering a standard data logger. 

Once you have your temperature recorder, you will 

need to choose material to serve as the “wick” to 

cover the tip probe. Water evaporating from the wick 

will reduce the temperature recorded, giving an 

indication of evaporative cooling. The wick should be 

made from an absorbent material, preferably cotton. 

It should also be constructed of two phases: a loose, 

absorbent interior, and an exterior that is of an 

absorbent tighter meshing material. The exterior 

keeps the inner absorbent material around the

sensing portion of the temperature probe and

prevents the sensing portion of the recorder from

being exposed to direct ambient conditions. You may

wish to purchase wicks commercially, such as from an online supplier 

(http://www.wickstore.com/wetbulbwick.html), or a good substitute is a round cotton bootlace 

(image 2). See page 34 for more information on supplies for a wet bulb thermometer.

There are several simple steps to setting up a wet bulb thermometer. 

1. Gather materials. You will need a vessel for holding water which must either be

refilled during processing, or must be

sufficiently large to hold enough water

(allowing for evaporation) to keep the water

level close to the temperature probe.

Choosing a vessel with a small diameter

opening will reduce evaporation. Once a

water vessel has been chosen, simply fill it

with water. You will also need a temperature

measuring device and material to serve as a

wick. In image 3, the bottom of a soda bottle

2 

and a glass beaker are pictured as vessels. 3 

Both an instant read and a data logger are shown for measuring temperature and 

pieces of brown cotton shoelace serve as the wick. 

2. Assemble the wet bulb thermometer. Cut a 

portion of the wicking material (it should be 

long enough to reach the bottom of the water 

vessel and than some). Connect the sensing 

portion of your temperature recorder to the 

wick by inserting the probe/wire/stem into the 

center of the wick (image 2). Secure the end 

of the wick to the probe/wire/stem using tape.

4 Place the wick in the water-containing

vessel. Make sure the wick is completely
34

saturated with water, then position the wick-covered sensing portion of your 

temperature recorder so that it is completely exposed to ambient conditions, yet as 

close as possible to the water source (image 4). This will ensure adequate wicking 

of the water to the sensing portion of the temperature recorder. If exposure to 

ambient conditions is too great, such as when the wick is too long or the recorder too 

far from the water surface, the wick may dry out, and evaporative cooling will not be 

recorded.

3. Place the wet bulb thermometer inside the chamber. If you are using an instant

reading temperature measuring device to

make process adjustments, place the wet

bulb thermometer for easy access and

readability, such as near a door or window

(image 5). If immediate feedback is not a

consideration (image 6), place the device

where the ambient conditions of your process

are least likely to give you optimum conditions

5 - hence a “worst case” reading. Position the

wet bulb thermometer in a flow of air (such as

in a stream of incoming air), but away from fans

which will cause excessive evaporation and

drying of the wick.

4. Record wet bulb temperature. Establish a

regular schedule of recording or down-loading

wet bulb temperature. Check water level in the

vessel periodically, and also check the position of

the wick. The portion of the wick above the water

must remain moist for accurate temperature

measurement. The wet bulb temperature can be

used to adjust your process conditions, as needed.

Supplies for Making a Wet Bulb Thermometer*

Instant Read Temperature Recorders

Fisher Scientific (800-766-7000)

• Part 15-078-38; price $131.49 plus shipping

• Part 15-077-14; price $111.15 plus shipping

Data Logger-Type Temperature Recorders

Dickson Company (800-323-2448)

• Part SM325 (LCD Display Temperature Data Logger w/ 2 K-thermocouple probes); 

price $399 plus shipping

• Also order software to download information to computer ($79)

Wick Material

• Round cotton bootlace (pictured in this document) - available at many general stores • 

Wet-bulb wick ($50-$60 per spool http://www.wickstore.com/wetbulbwick.html)

6 
35

• Wet-bulb sock: Alkar, part #50040; price $127.00 for bundle of 100 (608-592-4865) 

*The items and suppliers listed here are suggestions only, based on price and 

availability. The mention of particular suppliers is not meant to exclude others from 

consideration. 

For more information contact: 

Steve Ingham, Extension Food Safety Specialist (608) 265-4801, scingham@wisc.edu 

May, 2006 

The University of Wisconsin-Madison Center for Meat Process Validation provides science-based HACCP support to 

small meat processors in meeting state and federal mandates for safe food processing and handling. For more information 

on the Center contact Dr. Steve Ingham, 1605 Linden Drive, UW-Madison, Madison, WI 53706 (608) 265-4801 Email: 

scingham@wisc.edu