2.4. Bacterial enumeration
After microwave heating treatment, 25 g of sample was mixed with 50 ml of 0.2 % PW pre-chilled in ice-water to rapidly cool the sample, thus reducing the effect of residual heat. Then, the sample and 0.2 % PW mixture was diluted with 175 ml of sterile 0.2 % PW and homogenized for 2 min in a stomacher (EASY MIX, AES Chemunex, Rennes, France). After homogenization, 1 ml aliquots of homogenized samples were ten-fold serially diluted in 9 ml of sterile 0.2 % PW, and 0.1 ml of sample or diluent was spread-plated onto XLD for the enumeration of S. Senftenberg, Typhimurium, and Tennessee. Where low populations of surviving cells were anticipated, 1 ml aliquots of the original homogenate were equally distributed between four plates and spread-plated. All plates were incubated at 37 °C for 24 h and colonies were counted. Experiments were conducted three times.