To ensure food safety during emergency events such as nuclear disasters, we developed a practical rapid determination method for strontium-90 (Sr-90) in foods. Purification of Sr from foods was simplified using a commercial Sr-extraction column. We also reduced the waiting time to achieve radiative equilibrium between Sr-90 and Y-90. Finally, we developed a rapid determination method for Sr-90 that can be completed in about a week. Using the new method, stable Sr recoveries exceeded 85%. The trueness of the method ranged from 109 to 115% and the detection limit of Sr-90 was estimated to be 0.07 Bq/kg fresh weight according to a performance evaluation using standard materials. Sr-90 radioactivity concentrations in food samples determined by the new method were highly correlated and nearly equal to concentrations determined by the conventional method. The present study suggests that the new method offers highly sensitive and rapid detection of Sr-90 which are necessary attributes for food tests during emergency events.

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.

The inhibition of Kudoa septempunctata by green tea extract, black tea extract, and coffee extract were studied. Incubation of about 10⁴ Kudoa spores with green tea extract, black tea extract, or coffee extract at 25℃ for 4 hr reduced the survival ratio of Kudoa to 0%. While coffee extract and green tea extract contain approximately 2 and 1 mM of caffeine, respectively, the incubation of Kudoa spores with 2 and 1 mM of caffeine reduced its survival ratio to 68.2 and 93.3%, respectively. Although green tea extract and black tea extract contain over 1 mM of catechin, incubation with 0.01 mM of catechin was enough to reduce the survival ratio of Kudoa to 20%. These results suggested that green tea extract, black tea extract, and coffee extract have strong inhibitory effects on Kudoa and the effects of green tea extract and black tea extract are mainly manifested through catechin.