A study was designed to determine populations of aerobic bacteria, coliforms, sorbitol-negative bacteria, and Listeria monocytogenes during display at 4 and 12°C of ground beef patties made with meat from animals fed diets supplemented daily (for 100 days) with 0, 1,000, or 2,000 IU of vitamin E. The patties (113.5 g) were either left uninoculated or were inoculated with Escherichia coli O157:H7 or L. monocytogenes and were tray-overwrapped and stored (at 4 or 12°C for 8 to 10 or 4 to 6 days, respectively) while being continuously exposed to fluorescent light in a display setting. Patties were visually evaluated for overall appearance (based on color and/or discoloration) twice a day and analyzed for microbiological counts at 2-day intervals during display at 4°C and at 0, 1, 2, 3, 4, and 6 days during display at 12°C. Use of beef from animals fed supplemental vitamin E (“high-vitamin E beef”) resulted in ground beef patties which, when stored at 4°C, maintained visually acceptable color longer than did patties made from control beef (from animals not fed supplemental vitamin E), but effects on microbial growth were less pronounced. In general, use of high-vitamin E beef versus control beef in patty manufacture had no major effect on populations of aerobic bacteria, coliforms, sorbitol-negative bacteria, or L. monocytogenes in ground beef patties displayed at 4 or 12°C. Listeria monocytogenes multiplied at 12°C, but growth was similar among ground beef patties made from high-vitamin E beef versus control beef. Overall, changes in bacterial populations were similar in ground beef patties derived from meat from animals with or without added vitamin E in their diets, but control ground beef became visually unacceptable sooner.
Lessons from a large outbreak of Escherichia coli O157[ratio ]H7
infections: insights into the infectious dose and method of
widespread contamination of hamburger patties
