Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 22, 1996
Publication Date: N/A
Interpretive Summary: One of the recommendations from the National Cattlemen's Association's National Beef Tenderness Plan was to standardize protocol for the measurement of Warner-Bratzler shear force for use as an estimate of cooked meat tenderness in genetic evaluations. Currently used protocols vary widely among institutions and could result in different shear force values for the same animal. Thus, a series of experiments was conducted to determine the optimal protocol for obtaining Warner- Bratzler shear force values for cooked meat. Several factors related to the sample and its preparation for analysis would impact the result of shear force evaluation. Thus, those factors should be standardized to avoid introducing a bias into the data. Frozen steaks should be thawed to a consistent temperature (3 to 6 deg C) before cooking. Steaks should be cooked to a constant temperature end point rather than for a constant time (when using a Farberware electric broiler). Holding time after cooking should be standardized. At least five cores should be obtained from each steak, parallel to fiber orientation, and sheared once each in the center. Careful attention to these and all other aspects of the shear force protocol should assist the beef industry in culling live animals that produce tough meat by increasing the accuracy of shear force data and thus, of genetic selection for tenderness, regardless of the institution collecting the data.
A series of experiments was conducted to determine the effects of various factors on Warner-Bratzler shear force measurement of beef. As the extent of thawing of frozen steaks before cooking for shear force evaluation increases (-2 vs 12 deg C), shear force decreases (P < .05; 7.34 vs 5.99 kg). Location within the longissimus thoracis et lumborum from which steaks were obtained (caudal, medial, or cranial) did not affect (P > .05) shear force (5.21, 5.15, or 5.26 kg) or any sensory trait. Mean shear force of longissimus steaks cooked to either a constant temperature of 70 C (6.97 kg) or for a constant time of 30 min (6.38 kg) was not different (P = .06), but shear force repeatability was higher for steaks cooked to constant temperature (.79 vs .53). Mean shear force (6.20 vs 6.33 kg) and shear force repeatability (.74 vs .68) of longissimus steaks cooked by either electric broiler or convection oven broiler, respectively, were not different (P > .05). Meat cores obtained perpendicular to the steak surface, from one location within the muscle, had lower (P < .05) mean shear force (3.41 vs 4.17 kg) and much less repeatable shear force (.12 vs .66) than cores obtained parallel to muscle fiber orientation. Use of more than five cores per animal did not significantly increase repeatability of mean shear force. Numerous factors must be carefully controlled to ensure measurement of shear force is as accurate and repeatable as possible.