cience of meat..). Another factor in tenderness is sacromere length. The sacromere is the unit which allows the muscle to relax or contract. Longer sacromeres result in more tender beef. Finally, marbling is an important aspect of beef tenderness. It makes cooked beef more tender because fat is less resistant to force than muscle fibers or connective tissue (beef pro./manag. D.). However, the primary benefit of marbling to tenderness is a psychological one; it lubricates the mouth during chewing, causing the consumer to perceive a more tender cut than may actually be present (meat tenderness).
             Meat tenderness is in a small way related to genetics. Brahman and Brahman cross cattle with at least 50% Brahman genes historically produce beef that is less tender than other breeds. This is partially due to the presence of less proteolytic enzyme activity in the muscles of Bos Indicus cattle. When Brahman genes are found in 3/8 or less of an animals genetic makeup, and combined with other appropriate types, such as British breeds, the beef is more tender than in those with more Brahman genes. British breeds rank the highest in tenderness. Some sires have shown a genetic predisposition to tender meat within a breed (beef production/manag d.). The heritability of tenderness is approximately 45% (meat tenderness). The age of animal at slaughter also influences tenderness. As an animal grows older, there is an increase in cross linking within and between collagen molecules that makes them less susceptible to softening when cooking, and thus less tender. Fed steers and heifers produce the most tender beef between 12 and 24 months of age. Bulls that are fed concentrates have a window of opportunity up to 15 to 16 months of age, when tendernes
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