Influence of the chilling system on bacterial contamination and the quality of slaughter chicken carcasses

摘要

The aim of the research was to determine the quantity of nonspecific bacteria contamination, the presence of pathogenic bacteria, as well as the sensory qualities of slaughter chicken carcasses with regards to the implemented chilling system. The investigations were conducted on carcasses of broiler chickens, aged 6-8 weeks and a body weight of 1.2-2.5 kg, that had been chilled in three technologically different systems: air, immersion and evaporative chilling.The temperature of the carcasses was taken before and after chilling, the bacterial contamination was measured (total count of aerobic bacteria, total number of coliform, psychrotrophic and proteolytic bacteria), as well as a sensory analysis (appearance and odor) was conducted. The temperature of the carcasses after chilling was 4.28 degrees C, 6.97 degrees C after immersion chilling, and 4.39 degrees C after evaporative chilling. This data indicates that none of the mentioned systems lowered the temperature of the carcasses to that required by the regulatory limits of 4 degrees C. According to the authors' research the total count of aerobic bacteria in the case of carcasses chilled by air was 2.6 x 10(4) cfu per 1 g, chilled by immersion, 3.9 x 10(4) cfu, through evaporative chilling, 2.7 x 10(4) cfu/g. The bacterial contamination of carcasses chilled by water was significantly higher in comparison to both remaining chilling systems. The total number of coliforms in the case of carcasses chilled by air averaged 1.7 x 10 cfu/g, chilled by water 2.5 x 10 cfu/g, while through evaporative chilling 1.9 x 10(2) cfu/g. Only among carcasses chilled by immersion did the chilling system significantly differ the bacterial contamination of the coliform group from both remaining systems; it was higher in the case of immersion chilling. Air chilling and evaporative chilling did not differ among themselves in relation to this group of bacteria. The total number of psychrotrophic bacteria in the case of carcasses chilled by air averaged 10(3) cfu/g, chilled by immersion 1.2 x 10(4) cfu, chilled by the evaporative system 6 x 101 cfu/g. The chilling system significantly differed the contamination of the carcasses in the mentioned bacterial group; it was highest in the case of immersion chilling, and lowest with air chilling. The total number of proteolytic bacteria in the case of carcasses chilled by air averaged 1.8 x 10(3) cfu/g, chilled by water 2.9 x 10(3) cfu/g, while through evaporative chilling 3.1 x 10(3) cfu/g. The chilling system significantly differed the contamination of the carcasses only in the case of those chilled by air from the contamination confirmed after chilling by immersion as well as evaporative chilling. The level of proteolytic bacteria in the carcasses chilled in the latter two systems was similar. Salmonella rods occurred in the muscle tissue of chickens chilled in all systems. In the investigations, Salmonella was isolated most often in carcasses from immersion chilling (27% of the general sample), after which in those from evaporative chilling (20%), and least often after air chilling alone (13%). S. Enteritidis was the most often isolated pathogen. However, the chilling system did not affect the sensory qualities of the carcasses; their appearance and odor and from the perspective of sensory evaluation all the examined systems gave a high quality product.In the process of chilling poultry the highest quality chicken carcasses are gained from applying air chilling: the carcasses are relatively the best chilled and the least contaminated with nonspecific and pathogenic bacteria in comparison to those from immersion chilling and evaporative chilling. On the other hand the lowest quality product is gained from the immersion chilling of the carcasses, which are inadequately chilled and have the highest level of nonspecific and pathogenic bacteria in comparison to those from air and evaporative chilling. From the perspective of chilling, external water content