Effectiveness of a polyamide film releasing lactic acid on the growth of E. coli O157:H7, Enterobacteriaceae and Total Aerobic Count on vacuum-packed beef

The suitability of a polyamide 6 monolayer film containing lactic acid for use as an antimicrobial package for fresh beef cuts was studied. The release of lactic acid in an aqueous environment was immediate (within 1 h) and was from approx. 55 μg lactic acid/cm2 film at 0–8 °C to approx. 67 μg lactic acid/cm2 film at 12–20 °C. Beef was contaminated with an Escherichia coli O157:H7 isolate with known minimum inhibitory concentration against lactic acid (0.09% v/v), then wrapped with the lactic-acid polyamide film and vacuum packaged. During storage at 12 °C, the numbers of E. coli were 1 log unit lower than that of a control (untreated polyamide film) and decreased by an additional 1 log during storage for 14 days.