Abstract: Microbial samples collected from a representative mutton slaughter and processing plant in Suzhou, Jiangsu province, China were detected. This study mainly focused on the processing of cooked products, including the contact surfaces of cooking workshop, the air in each processing workshop, raw meat before and after washing and cooked meat. The aim was to determine the distribution of contaminating microbiota during the industrial production of cooked meat products. Bacterial counts of all the air samples were lower than 10 CFU per plate, respectively, being in line with the air quality standards. However, the total colony number of cooked meat reached 3.23(lg(CFU/cm2)) due to cross-contamination with the seriously polluted contact surfaces of cooking workshop. The contaminating spoilage bacteria were identified to be mainly Bacillus, Staphylococcus saprophyticus, Proteobacterium, Chryseobacterium and Microbacterium based on a combination of morphology and 16S rDNA sequences. Subsequently, three dominant spoilage bacteria, Bacillus sp. M1, S. saprophyticus M7 and Bacillus sp. M9, were selected to evaluate their potential for cooked mutton spoilage by detecting sensory scores, pH value, total colony number, total volatile basic nitrogen value and yield factors of microbial metabolites. The results suggested that Bacillus sp. M1 displayed the strongest spoilage potential, followed by S. saprophyticus M7 and Bacillus sp. M9. This study may provide a theoretical basis for microbial pollution control of cooked mutton products.

Key words: mutton slaughter plant, spoilage bacteria, Bacillus, Staphylococcus saprophyticus, spoilage potential