Effects of Energy Intake and Feed Source on Chemical Changes and Flavor of Ground Beef during Frozen Storage

Thirty-nine steers were divided into 13 trios according to breed, body type and weight and subsequently wintered on a silage ration. From April 14 to no later than August 14, a member of each trio was finished either on (1) orchard grass, fescue and clover pasture (low energy, grass fed), (2) a limited grain ration (low energy, grain fed), or (3) grain ration ad libitum (high energy, grain fed). Steers in each trio were slaughtered as a group during first two weeks of August, 1976, and each carcass was chilled 72-hr at 1.6 C prior to fabrication. Flavor, selected chemical characteristics and fatty acids of neutral and polar lipids of ground beef (20% fat) prepared from the semimembranosus muscle and brisket fat of each carcass were determined after 30 and 180 days storage at −18 C. A selected panel scored flavor of ground beef from steers limited or full fed grain higher (P<.001) than ground beef from grass fed steers. Flavor score did not change significantly during storage. Free sugar content was higher in beef from grain fed than grass fed steers. Ground beef from low energy fed steers had higher amounts of free fatty acids (FFA) and lower TBA values. In all feeding treatments, free sugars, FFA and TBA content increased during storage. Ground beef from grass fed steers had less C16:0 and more C18:3 in neutral and polar lipids and more C18:0 in the neutral lipids than ground beef from limited grain fed steers. Ground beef from steers fed low energy rations had more C18:0 and C18:3 and less C18:l and C18:2 in neutral and polar lipids, more C16:l and less C14:l in neutral lipids and less C22:0 in polar lipids than ground beef from steers finished on high energy ration.