Shear gradient in longissimus steaks 1 C. R. Kerth 2 , J. L. Montgomery 3 , J. L. Lansdell 4 , C. B. Ramsey, and M. F. Miller 5 Animal Science and Food Technology Department, Texas Tech University, Lubbock 79409-2162 ABSTRACT: Boneless top loin subprimals (n = 320) from Slight and Small marbled carcasses were fabri- cated into 2.54-cm thick steaks to determine core loca- tion effects on tenderness. In Exp. 1, top loins were aged to 7 d before steaks were cut and cooked to an internal temperature of 71°C. After cooking, a maxi- mum of 15 1.27-cm diameter cores were removed and sheared with a Warner-Bratzler shear force (WBSF) device. There was not a marbling score × core location interaction (P = 0.36). However, there was a main effect of core location (P < 0.01). Cores from the medial, mid- dle, and lateral portion of the longissimus muscle (LM) aged for 7 d differed, with less resistance (P < 0.05) in the medial than the lateral end. Also, there was an effect of marbling score on WBSF, with Small-marbled steaks having lower (P < 0.02) WBSF values than Slight-marbled steaks. In a second experiment, steaks were removed from the middle of the top loin subpri- Key Words: Beef, Meat Quality, Tenderness 2002 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2002. 80:2390–2395 Introduction Morgan et al. (1991) and Brooks et al. (2000) reported that tenderness is unacceptably inconsistent. Many fac- tors affect beef tenderness of the longissimus muscle 1 This research was partially supported partially by the Cattle- man’s Beef Promotion and Research Board through the Beef Industry Council of the National Live Stock and Meat Board. Names are neces- sary to report factually on available data; however, Texas Tech Uni- versity does not guarantee nor warrant the standard of the product, and the use of the name by Texas Tech University implies no approval of the product to the exclusion of others that may also be suitable. Manuscript No. T-5-409 of the Texas Tech University College of Ag- ricultural Sciences and Natural Resources. 2 Current Address: Animal and Dairy Science Department, Auburn University, 140 Upchurch Hall, Auburn, Alabama 36849. 3 Current Address: Intervet Inc., 405 State Street, Millsboro, Dela- ware 19966. 4 Current Address: Continental Deli Food Inc., 2601 Northwest Expressway, Suite 1000W, Oklahoma City, Oklahoma 73112. 5 Correspondence: Box 42162 (phone: 806/742-2804; fax: 806/742- 0169; E-mail: mfmrraider@aol.com). Received October 2, 2001. Accepted May 13, 2002. 2390 mals and aged an additional 7 d to produce 14-d aged steaks. Shear values decreased (P < 0.05) from Exp. 1 to 2 for all core locations. Neither the main effect of marbling score nor the core location × marbling score interaction was significant (P > 0.40); however, the same lateral to medial gradient in WBSF values was discovered again in Exp. 2. Both experiments indicated there were regions of WBSF values that differed (P < 0.05) across the cross section of the LM producing a shear-force/tenderness gradient, with the most medial cores having the lowest WBSF values in both experi- ments independent of marbling score. Regression anal- yses indicated the middle and center portions of LM steaks tended to have the most predictive capacity of average WBSF. Because of the variability in tenderness caused by location within the LM, care should be exer- cised when selecting sampling areas for the measure- ments of tenderness using the WBSF measure. (LM) including cookery (Cover and Hastetler, 1960; Machlik and Drandt, 1963; Hedrick et al., 1968), degree of doneness (Visser et al., 1960; Cover et al., 1962), measurement techniques (Bratzler and Smith, 1963; Sharrah et al., 1965; Wheeler et al., 1996), and muscle sample location within a single muscle (Ginger and Weir, 1958; Taylor et al., 1961). A number of researchers have investigated potential tenderness gradients across the LM (Alsmeyer et al., 1965; Hostetler and Ritchey, 1964; Crouse et al., 1989). Increased marbling in the LM also has been reported to improve the palatability and tenderness and decrease Warner-Bratzler shear force (WBSF) values (McBee and Wiles, 1967; Smith et al., 1984; Wheeler et al., 1994). However, Berry (1993) is the only study to these authors’ knowledge to determine Slight and Small mar- bling effects and core location effects on beef tender- ness. Unfortunately, Berry (1993) did not determine differences in WBSF within the entire cross section of the LM, just the dorsal edge of steaks. Therefore, the objectives of the present study were to elicit the impact of core location within steaks with marbling scores of Slight and Small on WBSF values of beef LM. A second- ary objective was to determine how individual core loca-