The factors affecting the tenderness of beef are numerous, and include such diverse items as breeding, feeding and management, anatomy, cellular activity, enzymes, chemical changes, both analytical and physical, and cooking technics. Workers in a number of laboratories have been exploring various of these areas.Beef generally is considered to be tender when first slaughtered, to become less tender with cold storage up to 48 hours, and then gradually to increase in tenderness as the storage period is lengthened. However, previous work by Paul, Lowe, and McClurg (1) indicated that beef cooked by roasting was least tender immediately after slaughter, and became increasingly tender with cold storage. Following the cooking method used by Ramsbottom, Strandine, and Koonz (3), exploratory work by Paul, Bratzler, and Knight (Z), suggested that beef steaks cooked by frying in deep fat were more tender immediately after slaughter than after 24 to 48 hours of cold storage. It was postulated that the slow heating of beef in roasting hastened the development of rigor so that the roast became tough before being completely cooked, while the very rapid heating of the thinner steaks in deep fat frying prevented the development of rigor in the fresh samples. I n order to test this theory, a series was designed to give direct comparisons of tenderness of roasts cooked in the oven with tenderness of steaks cooked in deep fat, after various periods of storage after killing.
PROCEDUREThe semitendinosus and biceps femoris muscles from 6 animals were utilized. Two of the carcasses were graded prime, 2 good, and 2 commercial. Each muscle was divided into 3 adjacent pairs of one-inch steaks and three-to four-inch roasts. The 6 pairs of steaks and roasts from each pair of muscles (right and left) were distributed at random over the various storage times of 0, 5, 12, 24, 45-53, and 144-149 hours. The time between stunning the animal and putting the meat on to cook or into cold storage was approximately one hour. After the appropriate period. of storage at 4-7"C., each pair was cooked and sampled. The steaks were fried in deep f a t a t 147°C. to an internal temperature of 63°C. The roasts were cooked in an oven a t 163°C. to the same internal temperature as the steaks. One-half inch cores were sheared on the Warner-Bratzler shearing machine for evaluation of tenderness. Records were kept of cooking times and losses. The p H of the raw meat was determined.Samples for microscope examination were fixed in 10% formalin, sectioned on the freezing microtome, stained with Harris haemotoxylin, and mounted in glycerine jelly."Journal article No. 1373 (N.S.) from the Michigan Agricultural Experiment S t a tion.
