Application of an Estimation Method of Microbial Concentration of a Food Sample from Qualitative Data

Microbial concentrations of thermally processed foods are mostly low. Recently we proposed a stochastic method based on the MPN technique for estimating microbial concentration in a food product whose concentration is low. Namely, with the number of target pathogen-positive samples in the total samples of a food product by a qualitative examination, the concentration of the target microbe in the product was estimated with the stochastic method. However the credible interval of the estimate with the method was not yet studied. Also the method was not validated with foods yet. The present study showed the 95% credible interval of the estimation by the method with the maximum likelihood analysis. Also the present study showed the reliability of the method experimentally by using a powdered formulae for infants product and a liquid food model injected with Salmonella cells. This method could estimate as low as seven and two cells/1,000 g or 1,000 mL, respectively. Next, the estimated concentrations and 95% credible intervals of Enterobacteriaceae in fresh meat for eating raw were demonstrated at various Enterobacteriaceae-positive numbers of the sample with the present method. Further, the characteristics of the present method on the sample size and the aliquot of sample were clarified. These results suggested that the present method could be a good tool to verify microbiological safety of food products.