Applying Predictive Microbiology and Microbial Risk Assessment to Assess the Risk of Ready-to-Eat Food Products in Taiwan Based on Consumption Habits

Introduction: In Taiwan, the major etiologic agents of foodborne illness are bacteria. Ready-to-eat (RTE) products are consumed directly without reheating and therefore, pose a higher risk to consumers than other types of foods. Mayonnaised rice is a RTE product that may be a major cause of staphylococcal poisoning in Taiwan.

Purpose: The purpose of this study was to evaluate the relative risk of staphylococcal poisoning caused by mayonnaised rice through quantitative microbial risk assessment (QMRA). 

Methods: Samples of mayonnaised rice were collected from local convenience stores to test for the presence and concentration of Staphylococcus aureus to establish the baseline for QMRA. The storage conditions and consumption patterns of mayonnaised rice were identified. Inoculated studies were conducted to establish the growth kinetics of Staphylococcus aureus. The growth models were developed using the USDA Integrated Pathogen Modeling Program (IPMP 2013). Finally, QMRA was conducted using @Risk to evaluate the relative risks of staphylococcal poisoning.

Results: Dried meat floss onigiri containing mayonnaise may pose a high risk to consumers due to its frequent association with S. aureus. Analytical results showed that the annual average risk probability of staphylococcal poisoning caused by this product in Taiwan is 7.5×10^-11, and the storage temperature and the initial contamination levels are the most important two factors contributing to the risk. The safe storage time for spring, summer, fall and winter seasons are 18, 12, 16, and 34 hours, respectively.

Significance: The safest way for consumers to store mayonnaised rice is refrigeration. The retailer must properly control temperature during storage and distribution.