Survival of Salmonella spp. in half carcasses of chicken broilers during microwave cooking

摘要

The aim of the study was to determine the survival of Salmonella spp. in chicken half carcasses subjected to microwave heating for 6-16 minutes. Three strains of Salmonella spp. were used in the study: Salmonella Enteritidis No. 42/93, S. Typhimurium No. 11/93 and S. Anatum No 310/81, obtained from the National Veterinary Institute in Pulawy. Chilled half carcasses with an average temperature 4 +/- 2 degrees C were immersed for 5 minutes in a bacterial suspension, prepared using the McFarland scale according to turbidity standard 0.5. Using templates of delimited surface 25 cm(2), two swabs were sampled from the external surface (thoracic and femoral region), and 2 from the internal surface (body cavity). Half carcasses' contamination (both control and heated) were determined by the most probable number (MPN) method, and the identification of viable colonies was carried out according to the methodology given in ISO 6579: 2007 + A1 Standard. Half carcasses were heated in a microwave oven with a power of 930 w, for 6, 8, 10, 12, 14 and 16 min. Then the temperature was measured at six different places of the half carcasses. Three repetitions of the experiment were performed with each bacterial strain (in total 162 heated half carcasses and 162 as a control were examined). The results show a significant effect of the weight of the half carcasses (p <= 0.05) on their temperature after heating. A negative correlation between temperature and weight of half carcasses and a positive one between temperature and applied heating time was observed. The temperature of the half carcasses, depending on their weight, ranged from 54.75 +/- 2.75 degrees C to 74.43 +/- 7.24 degrees C after 6 min. of heating, and from 81.68 +/- 6.77 degrees C to 91.28 +/- 3.95 degrees C after 16 min. In each of the applied heating times, large temperature differences measured at 6 different locations, up to 18.9 degrees C were determined; the lowest value of temperature was observed on the skin of half carcasses. The most sensitive strain was S. Anatum, followed by S. Typhimurium and S. Enteritidis. Regardless of the bacterial strain the reduction in the number and total inactivation of tested bacteria occurred more rapidly on the internal surface. Total destruction of S. Anatum from the initial contamination level of 3.11 +/- 0.11 log cfu/cm(2) in the body cavity and 3.24 +/- 0.06 log cfu/cm(2) on the skin was achieved after 12 and 14 minutes respectively. Elimination of S. Typhimurium and S. Enteritidis in the body cavity occurred after 14 min. of heating, with the initial contamination level of 4.51 +/- 0.09 and 4.30 log cfu/cm(2) +/- 0.02 log cfu/cm(2), respectively. The time required for elimination of the mentioned strains on the skin surface was longer - 16 min. The desired result i.e. total destruction of Salmonella spp. - was achieved by the combination of temperature with a sufficiently long heating time impact.