Lean color characteristics of bullock and steer beef.

Twelve young bulls and 12 steers were slaughtered and the carcasses were fabricated at 48 h postmortem. Top rounds, bottom rounds, and rib eyes were vacuum-packaged and stored at 0 degrees C until 21 d postmortem. After subprimal storage, steaks were removed from each cut and displayed under simulated retail conditions for 3 d. Consumer panelists (n = 110) showed little difference in buying preference for top round, bottom round, and rib eye steaks from steers vs bullocks. Also, consumer panelists could not detect color differences between steaks from steers and bullocks. Experienced panelists (n = 6) detected brighter (P less than .05) muscle color for top round and rib eye steaks from steers but detected no difference in muscle color of bottom round steaks from bullocks and steers. Generally, overall desirability scores favored steaks from steer carcasses. This was particularly true of rib eye steaks. Sex-class of carcass did not affect aerobic plate counts of top round, bottom round, or rib eye steaks either before or after 3 d of retail display. Muscle pH was lower for top round and rib eye steaks from steer carcasses; however, the magnitude of this difference was not large enough to affect retail display stability. Muscle pH of bottom round steaks was not affected by sex-class. Although experienced panelists could detect differences in visual appearance of beef retail cuts from steers and bullocks, consumer panelists did not show a clear purchase preference for steer vs bullock beef. These data suggest that beef retail cuts from bullocks are acceptable in visual appearance.

Effect of Growth of Individual Meat Bacteria on pH, Color and Odor of Aseptically Prepared Vacuum-Packaged Round Steaks.

Large increases in counts cf Leuconostoc spp., Lactobacillus coryneformis , Lactobacillus plantarum , Lactobacillus viridescens and Lactobacillus curvatus occurred over a 28-d display period when aseptically fabricated steaks were inoculated with 103 to 104 cells/cm2 of these species and then were vacuum-packaged. With Lactobacillus cellobiosus 2, Serratia liquefaciens or Hafnia alvei as inoculum, increases in count were much smaller. Counts of L. cellobiosus 1, Brochothrix thermosphacta , a Moraxella sp. and Alteromonas putrefaciens of inoculated steaks decreased during display. With a higher inoculum (106 cells/cm2), increases in counts of lactic acid bacteria usually were smaller. Some lactic acid bacteria caused marked decreases (0.2 to 0.5) in the pH of the meat surface. Changes in surface discoloration of uninoculated and inoculated steaks over a 28-d display period were not significant (P>0.05). Off-odor scores of both uninoculated and inoculated steaks were lower (more off-odor) after display but few of the differences were significant. Off-odors of steaks inoculated with lactic acid bacteria were described as "sour", "buttermilk", "sulfur-like" and "H2S".