Agricultural Quality Assessment Division QAD 1003B 

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Laboratory Proficiency Testing for Shear Force Measurements

1. BACKGROUND

The Department of Agriculture (USDA), Agricultural Marketing Service (AMS), Livestock and Poultry (LP) 

Program will certify carcasses and meat cuts for tenderness-marketing claims based on the American Society 

for Testing and Materials (ASTM) International tenderness standards. The basis for assessing tenderness that 

meets the performance requirements outlined in this document was established after consultation with an 

industry- working group convened by the LP Program. The Industry Working Group was comprised of 

representatives of USDA, industry associations, processing companies, producers, technology providers, and 

academia.

2. PURPOSE AND SCOPE

The Quality Assessment Division (QAD) 1003A: Operational Requirements for the USDA Certification of 

ASTM International Tenderness Marketing Claims specifies that slice shear force (SSF) or Warner-Bratzler 

shear force (WBSF) will be the methods of assessing tenderness. AMS approved third parties may conduct 

the SSF/WBSF testing required to validate that the requirements of an ASTM International tenderness 

standard have been met. Third party laboratories are approved to conduct SSF and/or WBSF through 

proficiency testing conducted in conjunction with an AMS designated SSF/WBSF reference laboratory. This 

document outlines the procedures and requirements of proficiency testing.

3. REFERENCE DOCUMENTS

A. QAD 1003A: Operational Requirements for the USDA Certification of ASTM Tenderness Marketing 

Claims. USDA LP Program. 

B. QAD 1000 Procedure: Quality Systems Verification Programs General Policies and Procedures. 

C. Research Guidelines for Cookery, Sensory Evaluation and Instrumental Tenderness Measurements 

of Fresh Meat. American Meat Science Association (AMSA), 1995.

D. Slice Shear Force Protocol for Large Volume. USDA, Agricultural Research Service (ARS). 

E. Standard Practice for Force Verification of Testing Machines. ASTM International Standard E4.

F. Standard Practice for User Requirements for Livestock, Meat, and Poultry Evaluation Devices or 

Systems. ASTM International Standard F 2341.

G. Standard Test Method for Livestock, Meat, and Poultry Evaluation Devices. ASTM International 

Standard F 2343.

H. QAD 1002 Procedure: USDA Quality System Assessment (QSA) Program. 

I. Warner-Bratzler Shear Force Protocol. USDA, ARS. 
Agricultural Quality Assessment Division QAD 1003B

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J. Wheeler, T.L., Shackelford, S.D., and Koohmaraie, M. Beeflongissimus slice shear force 

measurement among steak locations and institutions. Journal Animal Science 2007, 85:2283-2289

4. REQUIREMENTS

In addition to the required information as outlined in QAD 1000 Section 6, an individual or firm seeking to 

serve as an AMS approved party that conducts either SSF and/or WBSF testing must: (1) provide 

documentation that describes the quality management system as outlined in QAD 1002 Section 7; and, (2) 

demonstrate conformance with the elements below.

A quality management system must, at a minimum, specifically address the following:

• The organizational structure necessary to carry out these requirements;

• Requirements for the production of quality data;

• Control of documents, records and changes; and,

• Control and calibration of measuring and test equipment.

A. Operational Requirements

Testing SSF and/or WBSF instrument systems shall be used, operated, inspected, and maintained as 

described in ASTM International Standard F 2341. The areas addressed in this standard include instrument 

installation, operation, verification, inspection and maintenance, and operator training.

B. Test Samples

All testing will be conducted on 2.54-centimeter (one-inch) thick beef strip loin steaks from thirty strip loins. 

The strip loins shall include the following distribution of SSF as determined by the reference lab: for SSF, 

not more than 75% < 17 kg and at least 10% > 25 kg; and for WBSF, not more than 75% < 4.1 kg and at 

least 10% > 5.0 kg. Tenderness variation will be accomplished by varying or minimizing postmortem aging 

and may include other means to ensure that a sufficient distribution exists.

The strip loins shall be obtained by the third party lab and shipped to the reference lab as soon as possible 

after harvest such that the reference lab can freeze 15 of the strip loins no later than 3 days postmortem and 

another 15 strip loins no later than 14 days postmortem. If the 3 day postmortem requirement cannot be met, 

then all 30 strip loins should be frozen no later than 7 days postmortem.

Four steaks from the thirty strip loins (n = 120) will be tested by both the reference and third party labs. The 

reference lab will cut the frozen strip loins into 2.54-centimeter (one inch) thick steaks. The reference lab 

will assign two sets of two adjacent steaks to the third party lab and two sets for the reference lab in a manner 

that accounts for the potential location variation in shear force: reference lab steaks 1 & 2, third party lab 

steaks 3 & 4, reference lab steaks 5 & 6, third party lab steaks 7 & 8, with this order alternating among strip 

loins.

Randomly numbered frozen steaks will be labeled and shipped overnight by the reference laboratory to third 

party laboratories participating in the proficiency testing.
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C. Equipment

Cooking. Accurate shear force can be accomplished using a variety of cooking methods using constant time 

or constant temperature endpoints (Wheeler et al., 2007). Cooking should be conducted in a manner and 

with a method known to provide consistent results. The cooking endpoint target is 71°C (160°F) (AMSA 

Research Guidelines for Cookery, Sensory Evaluation and Instrumental Tenderness Measurements of Fresh 

Meat). Internal steak temperature must be measured with a calibrated thermometer. Steak weights must be 

obtained with a calibrated scale with appropriate weighing capacity.

Shearing. Several testing machines are available that can be equipped with SSF or WBSF attachments (see 

Slice Shear Force Protocol for Large Volume, and, Warner-Bratzler Shear Force Protocol, USDA, 

Agricultural Research Service). Instruments should be equipped with a load cell appropriate for the normal 

operating range for SSF or for WBSF. Instruments must be properly calibrated and operated in accordance 

with the manufacturer's instructions.

D. Method/Procedure

Shear force measurements should be conducted as described in protocols by USDA, ARS U.S. Meat Animal 

Research Center (see Slice Shear Force Protocol for Large Volume, and, Warner- Bratzler Shear Force 

Protocol, USDA, ARS).

E. Data Collection

Data should be recorded in the spreadsheet provided by the reference laboratory. Data recorded for each 

individual steak will include: frozen weight, refrigerator temperature, internal thawed temperature, cooking 

instrument (make and model), cooking time and temperature, internal cooked temperature, cooked weight, 

total thaw/cook loss, SSF or WBSF.

F. Performance Assessment

The reference lab and the third party lab(s) will send completed data spreadsheets to USDA-LP for 

performance assessment. Despite measures taken to ensure an adequate level of variation in shear force 

measurements, the amount of variation in a given dataset will impact all statistics associated with shear force. 

To account for this fact, performance criteria will be normalized to the reference lab. Proficiency will be 

determined by conformance to the following key performance elements.

5. REQUIRED KEY PERFORMANCE ELEMENTS

• Repeatability of duplicate samples must be at least 90% of the repeatability of the reference lab.

o Repeatability will be measured as: R = o2 sample/(o2 sample + o2 error)

• Accuracy measured by difference from the reference lab. The mean SSF or WBSF of the third party 

lab cannot be less than (P < 0.05) the corresponding mean SSF or mean WBSF for the reference lab.

It is permissible for the third party lab to have a higher mean than the reference lab because this will 

result in a more conservative approval for tenderness labeling.

• Precision measured by the standard deviation of the differences (rSD). The ratio of the third party 

lab rSD to the reference lab rSD must be < 1.40.
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6. APPROVAL PROCESS

Interested parties must submit their quality management plan and supporting data for review through a desk 

audit to the LP Program. Once the desk audit is satisfactorily completed, the quality management system is 

verified through an onsite audit conducted by the LP Program. In addition, the SSF and/or WBSF 

instruments will be verified over each third of the normal operating range that encompasses the tenderness 

standards (adapted from ASTM International Standard E 4 and F 2343). Once the onsite audit is 

satisfactorily completed, approval will be granted.

7. ADDITIONAL INFORMATION

You may find more information about a documented quality management program in QAD 1000 Procedure:

Quality Systems Verification Programs General Policies and Procedures and QAD 1002 Procedure: USDA 

Quality System Assessment (QSA) Program.

Questions or comments pertaining to these performance requirements and/or quality management program 

plan and performance assessment data spreadsheets should be submitted to:

David Bowden, Jr., Branch Chief

USDA, AMS, LP Program

1400 Independence Avenue, S.W., Stop 0258

Washington, DC 20250

Phone: (202) 690-3148

Email: david.bowden@usda.gov

_______________________________

David Bowden, Branch Chief

Livestock and Poultry Program

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