Beef longissimus slice shear force measurement among steak locations and institutions

The objectives of this study were 1) to determine which longissimus thoracis et lumborum steaks were appropriate for slice shear force measurement and 2) to determine the among and within institution variation in LM slice shear force values of 6 institutions after they received expert training on the procedure and a standard kit of equipment. In experiment 1, longissimus thoracis et lumborum muscles were obtained from the left sides of 50 US Select carcasses. Thirteen longissimus thoracis and 12 longissimus lumborum steaks were cut 2.54 cm thick from each muscle. Slice shear force was measured on each steak. Mean slice shear force among steak locations (1 to 25) ranged from 19.7 to 27.3 kg. Repeatability of slice shear force (based on variance) among steak locations ranged from 0.71 to 0.96. In experiment 2, the longissimus thoracis et lumborum were obtained from the left sides of 154 US Select beef carcasses. Eight 2.54-cm-thick steaks were obtained from the caudal end of each frozen longissimus thoracis, and six 2.54-cm-thick steaks were obtained from the cranial end of each frozen longissimus lumborum. Seven pairs of consecutive steaks were assigned for measurement of slice shear force. Seven institutions were assigned to steak pairs within each carcass using a randomized complete block design, such that each institution was assigned to each steak pair 22 times. Repeatability estimates for slice shear force for the 7 institutions were 0.89, 0.83, 0.91, 0.90, 0.89, 0.76, and 0.89, respectively, for institutions 1 to 7. Mean slice shear force values were least (P <0.05) for institutions 3 (22.7 kg) and 7 (22.3 kg) and were greatest (P <0.05) for institutions 5 (27.3 kg) and 6 (27.6 kg). Institutions with greater mean slice shear force (institutions 5 and 6) used cooking methods that required more (P <0.05) time (32.0 and 36.9 min vs. 5.5 to 11.8 min) to reach the end point temperature (71 degrees C) and resulted in greater (P <0.05) cooking loss (both 26.6% vs. 14.4 to 24.1%). Differences among institutions in the repeatability of slice shear force were partially attributable to differences among institutions in the consistency of steak thawing and cooking procedures. These results emphasize the importance of sample location within the muscle and cooking method in the measurement of tenderness and indicate that with proper training and application of the protocol, slice shear force is a highly repeatable (R approximately 0.90) measure of beef LM tenderness.