Combined effect of irradiation and organic acid treatment on the inactivation of Shiga toxin-producing Escherichia coli inoculated on beef trimmings

CAP, M.; CINGOLANI, C.; LIRES, C.; VAUDAGNA, S.R. ; LEOTTA, G.; HORAK, C.

Sorrento

Workshop; 2018 IFT-EFFoST International Nonthermal Processing Workshop and Short Course; 2018

ProdAl Scarl y Universidad de Salerno, Italia

The contamination of beef products with Shiga toxin-producing Escherichia coli (STEC) is a main concern for the meat industry, as STEC has been frequently associated with outbreaks implicating beef products. Irradiation is a well-known method for controlling microorganisms. International organizations, such as the WHO, IAEA and FAO, have officially pronounced the safety and wholesomeness of food irradiation. Organic acids also have an antimicrobial activity, due to their ability to reduce the pH, resulting in a stress for bacterial cell. The aim of this study was to assess the effectiveness of irradiation combined with lactic acid or caprylic acid on the inactivation of STEC inoculated on beef trimmings. Native strains included in STEC pool were O26, O103, O111, O145 and O157. Sample consisted of 25 g of beef trimmings inoculated with 50 µl of STEC pool in order to obtain a final concentration of 7 log CFU/g. Applied treatments were: lactic acid 0.5%, caprylic acid 0.04%, irradiation 0.5 kGy and the same irradiation dose combined with lactic acid o caprylic acid. Effectiveness was assessed by estimating log reductions after treatments. For that matter, samples were analyzed 24 h after acid treatments and immediately after irradiation treatment. Microbial counts were performed in Tryptone soy agar (TSA) and MacConkey agar (MAC). Organic acid and/or irradiation treatments resulted in the reduction of STEC in beef trimmings. The most effective one was irradiation, causing a 1.6 log CFU/g reduction. Lactic acid treatment caused a 0.1 log CFU/g reductions while caprylic acid treatment caused a 0.3 log CFU/g reduction. No synergistic effect was observed after the combination of organic acid with irradiation.The results suggest that there are no benefits from the combination of organic acid treatments, at those concentrations, with irradiation as far as the inactivation of STEC is concerned.