Keeratipibul Suwimon, Lekroengsin Sumalin
Department of Food Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
J Food Prot. 2008 May;71(5):946-52. doi: 10.4315/0362-028x-71.5.946.
The risk of Listeria spp. contamination was assessed in frozen ready-to-eat chicken meat production lines by establishing a mathematical model for determining the probability of Listeria spp. prevalence on environmental surfaces directly in contact with the product at various times in a chicken plant in Thailand. Environmental surfaces were divided into three zones. Zone 1 included surfaces in direct contact with products. Both zones 2 and 3 included indirect contact surfaces; zone 2 was next to zone 1, and zone 3 was next to zone 2, relatively far from the product. The model for probability of Listeria spp. contamination on surfaces in zone 1 was derived from the probability of Listeria spp. on surfaces in zone 1 after the cleaning and sanitizing process multiplied by the probability of Listeria spp. transferred from zones 2 and 3 and the probability of Listeria spp. growth. The surfaces in zone 1 were cleaned with warm water, cleaned with detergent, and sanitized with a sanitizer. Factors affecting cleaning and sanitizing were water temperature, concentration, and contact time of detergent and sanitizer. The probability of Listeria spp. prevalence on surfaces in zone 1 was not affected by water temperatures of 50, 60, and 70 degrees C and detergent concentrations of 0.5, 1, and 2% (vol/vol) at contact times of 5, 10, and 15 min. However, it was affected by sanitizer concentrations of 0.25, 0.5, and 1.25% (vol/vol) at contact times of 5, 10, and 20 min. Sensitivity analyses were conducted using the Monte Carlo simulation. The sanitizer concentration had the most significant influence on the prevalence of Listeria spp. on surfaces in zone 1. The prevalence of Listeria spp. on surfaces after cleaning and sanitizing, the production time, and the contact time with the sanitizer were highly correlated with the prevalence of Listeria spp. in zone 1. This model could be used as a management tool for assessing the risk of Listeria spp. contamination in food products.
