Mesophilic aerobic microbial populations in fresh ground beef were enumerated with a new system, Petrifilm™ SM Plates (PSM), and with the conventional aerobic plate count (APC) method using standard methods agar (SMA). Total colony-forming units were determined in 119 fresh ground beef samples (29 extra-lean, 30 lean and 60 regular) purchased at nine different retail markets over a period of 6 wk. Linear regression analysis of PSM vs. APC counts gave a slope of 0.963, an intercept of −0.027, and a correlation coefficient of 0.951. Mean log10 counts on PSM were 5.86 compared to 6.11 on SMA (P<0.01) or a mean log10 difference of −0.25. These analyses indicate that the Petrifilm SM method would be a possible alternative for the aerobic plate count method.
1Consulting statistician, Riker Laboratories, Inc., 3M Center, St. Paul, MN 55144.
2Present address: University of Florida, Department of Food Science and Human Nutrition, Gainesville, FL 32611.