[Evaluation of Decontamination Methods using Peracetic Acid for Shiga Toxin-producing Escherichia coli on the Surface of Beef Sub-primal Cuts].

Peracetic acid formulation has received much attention in recent years as a surface disinfectant for beef. There are many reports on the bactericidal effect of peracetic acid formulation on beef surfaces. However, the application method of peracetic acid formulation aiming at the complete removal of Shiga toxin-producing Escherichia coli (STEC) from the surface of sub-primal cuts has not been evaluated. The objective of this study was to determine the condition under which peracetic acid formulation can be used to completely remove STEC from the surface of sub-primal cuts of beef.The effect of peracetic acid formulation was evaluated by immersing pieces of beef on whose surfaces E. coli O157:H7 were inoculated. To investigate the impact of peracetic acid concentration on bactericidal efficacy, small pieces (5 cm×5 cm×5 cm) of meat from five parts were immersed in peracetic acid at concentrations of 900 ppm and 1800 ppm for 30 min. The bacterial counts were decreased by 2.6-4.0 log CFU/cm² at 900 ppm, indicating a varying bactericidal effect depending on parts of beef. Conversely, at 1800 ppm, declines of 3.9-4.1 log CFU/cm² were observed, reaching the detection limit. To confirm the efficacy of peracetic acid formulation on the surface of sub-primal cuts, larger pieces (5 cm×20 cm×20 cm) of beef from nine parts were immersed in 1800 ppm peracetic acid for 30 min. As was the case with small pieces of beef, bacterial counts were decreased by 3.5-3.8 log CFU/cm² and reached the detection limit. Given the actual number of total viable bacteria on the surface of sub-primal cuts, the reduction in bacterial counts observed in this study is a condition that allows for complete removal of STEC from the surface of sub-primal cuts.Consequently, it can be concluded that the immersion in peracetic acid with a concentration of 1800 ppm for 30 min is the appropriate treatment to decontaminate STEC totally from the surface of sub-primal cuts of beef.