Investigation of Beef Quality by Analyzing Fatty Acids and Effects of Pre- and Post-harvest Management

by Ting Jiang, M.S. Washington State University December 2008 Chair: Mark L. Nelson Fatty acids in meat have obtained a lot of attention from both scientists and consumers because fatty acids are demonstrated to be closely related with human health and meat is an important food source, especially, for developed countries. Beef has been the most consumed red meat in the US and the argument exists on whether beef is a healthy meat for humans. Therefore, the fatty acids of beef were analyzed in this thesis. Different from many studies, we analyzed fatty acid composition from different fat locations within a beef steak and compared fatty acid composition between raw and cooked steaks. The main results showed that conjugated linoleic acid level was almost doubled in outer subcutaneous fat compared to lean muscle tissue, but polyunsaturated fatty acids with chain lengths longer than 18 were detected almost exclusively in lean muscle. Cooking did not have huge impacts on the fatty acid composition of beef steaks. Although it is important to produce healthier meat for consumers, eating quality (palatability) should never be overlooked or compromised. Previous studies have proved that a lot of factors can influence beef palatability, including diet and postmortem management such as aging. Since few studies were conducted to study the interaction effects between diet and postmortem aging on beef palatability, we assigned different aging methods (dryor wet-aging) within several diet regimes including two forage diets, one concentrate diet (heifers or steers), and one forage and iv concentrate combined diet. In addition, sensory evaluations were conducted on both beef steaks and ground beef. There were no diet by aging interactions, and no diet or aging effect on palatability attributes of beef steaks. However, diet by aging interactions existed for ground beef aroma, tenderness, and juiciness. Diet had relatively small (P>0.05) effects on ground beef sensory attributes compared to aging (P<0.05). The specific effects of aging on ground beef palatability attributes differed depending on feeding systems. The results of this thesis will be very helpful in interpreting the results of previous studies, improving the design of future studies, and providing useful suggestions for practical beef production.