Growth of Salmonella typhimurium and Mesophilic Organisms on Beef Steaks as Influenced by Type of Packaging

Abstract

Two trials, each utilizing 72 samples of fresh beef loin steak, were done to determine the effects of various packing systems upon growth of Salmonella typhimurium. Samples were inoculated with 105 cells/cm2 of the organism and randomly assigned to four packaging treatments: (1) overwrapping in oxygen-permeable film; (2) vacuum packaging; (3) packaging in barrier bags flushed with a 60% CO2: 40% O2 gas atmosphere then evacuated and sealed; and (4) packaging in barrier bags filled with a 60% CO2: 40% O2 gas atmosphere. Twelve steak samples were inoculated with S. typhimurium and 6 were uninoculated and served as a control in each treatment group. Samples were displayed in retail meat cases at 10 C for 3, 6 or 9 days, when they were evaluated for shrinkage and numbers of mesophilic organisms and S. typhimurium. Percent shrinkage was not affected (P>0.05) by packaging treatment. Counts of mesophilic organisms were similar (P>0.05) for vacuum- and gas-treated steaks, which were significantly lower (P<0.05) than counts from film overwrapped samples. Numbers of S. typhimurium increased significantly (P<0.05) during storage on samples wrapped with oxygen permeable film but remained low and fairly constant for vacuum- or gas-treated steaks. After 9 days of display, the film overwrapped steaks had greater (P<0.05) numbers of S. typhimurium than those of other treatments, whereas steaks held within the 60% CO2: 40% O2 gas atmosphere had lowest numbers overall.