DETERMINATION OF HISTAMINE-FORMING BACTERIA, TOTAL COLIFORM AND ESCHERICHIA COLI IN FERMENTED FOODS

Abstract

Fermented fishery food products have been generally sold in the local market, Thailand. These products were frequently contaminated with various microorganisms due to raw material and unhygienic production process. Determination of microbial contamination of fermented food products helps to assure safety for consumers. Therefore, the aims of the study were to determine total bacteria, total coliform, Escherichia coli and histamine producing bacteria from fermented fishery food products commercially distributed in several regions of Chumphon and Surat Thani provinces. Twenty-two samples of fermented fishery food products were randomly collected for bacterial contamination assay. All samples revealed the levels of pH and salt content in the range of 3.67-7.46 and 8.46%-29.69%, respectively. The bacterial contamination of the samples was tested by total plate count method. Determination of coliform bacteria and E. coli was examined by multiple-tube fermentation technique. Total bacteria, total coliform and E. coli of all samples were in the range of 2.15-7.54 log CFU/g, < 3-460 MPN/g and < 3-93 MPN/g, respectively. In addition, thirteen histamine-forming bacteria were found on histamine-forming bacteria isolation agar after incubation at 37°C for 4 days. Five isolates of histamine-forming bacteria named M1, M3, M9, M11, and M13 were selected to identify by molecular techniques. M1 and M3 were obtained from shrimp paste (Kapi) and M11 was obtained from fermented fish (Pla Pang Dang). They were identified as Enterobacter sp. M9 and M13 isolated from fermented fish (Pla Som and Pla Ra) were identified as Citrobacter farmeri and Staphylococcus kloosii, respectively.