Modeling for Survival of Clostridium perfringens in Saeng-sik, a Powdered Ready-to-Eat Food with Low Water Activity

Abstract

ABSTRACT Saeng-sik is a powdered ready-to-eat food with very low moisture that contains dried raw materials such as grains, fruits, mushrooms, and seaweeds. This product is consumed as a convenient and nutritious meal replacement. The objective of this study was to develop a mathematical model for predicting the survival of Clostridium perfringens vegetative cells and spores in saeng-sik as a function of temperature and to validate the model using saeng-sik samples with different microbial communities analyzed by matrix-assisted laser desorption–ionization time-of-flight mass spectrometry. Kinetic data for C. perfringens survival in saeng-sik fit well to the Weibull model with high goodness of fit (R2 = 0.92 to 0.98). The obtained δ values (required time for first decimal reduction) for each temperature were 19.62 to 864.86 h, and concave curves (p < 1) were observed under all experimental conditions (5 to 40°C). Kinetic parameters were further described in a secondary model as a function of temperature using a Davey model (R2 = 0.99). The developed model was validated by the bias factor, accuracy factor, and root mean square error, and the values were within acceptable ranges for predictive models, even for saeng-sik samples with different microbial communities. When saeng-sik was rehydrated according to the manufacturer's recommendations, germination and outgrowth of C. perfringens was observed when the sample was subjected to unusual temperatures during storage, such as at 30°C for 15 h. C. perfringens spores survived in saeng-sik with very low water activity. Because C. perfringens could germinate and grow under such conditions, care must be taken to avoid initial contamination of C. perfringens during the manufacturing process. Our model developed with samples with different microbial communities provides useful information for next-generation microbiological risk assessment taking into consideration the ecology of the food-associated microbial community. HIGHLIGHTS