Effect of Fat Content and Storage Temperature on the Growth and Survival Kinetics of Pathogenic Microorganisms in Milk and Ready to Eat (RTE) Quail Eggs

우유와 즉석섭취 메추리알에서 병원성 미생물의 생육에 미치는 지방과 저장온도의 영향

According to the microbiological standard, Staphylococcus aureus, Clostridium perfringens and Listeria monocytogenes should not be detected in milk and egg products in Korea. Refrigerated food such as milk must be kept under $10^{\circ}C$ at retail markets. However, temperature abuse of refrigerated foods at such markets is often observed. We compared the growth and survival kinetics of S. aureus and C. perfringens at 10 and $15^{\circ}C$, and the growth kinetics of L. monocytogenes at 4 and $10^{\circ}C$ in whole and skim milk and ready-to-eat (RTE) quail eggs to evaluate their growth possibilities at retail markets. Regardless of storage temperature, the level of S. aureus reached the maximum level ($10^8-10^9CFU/ml$) in whole milk, non-fat milk and RTE quail eggs within the expiration date. Even low contamination levels of S. aureus (10 CFU/mL) grew rapidly in milk and quail eggs to reach the maximum level within the shelf life. Survival of C. perfringens in whole milk was greater than that in non-fat milk, indicating that the fat content in milk influences the survival of C. perfringens. For L. monocytogenes, the population in milk increased by 0.5-1 log CFU/mL at $4^{\circ}C$, while the populations reached the maximum level at $10^{\circ}C$ within the expiration date, regardless of initial contamination levels. In quail eggs, L. monocytogenes grew to the maximum level within the expiration date (60 days) at both temperatures. S. aureus and L. monocytogenes must be controlled to be negative, and proper temperature management should be emphasized at retail markets to protect the consumer. Since C. perfringens did not grow in milk and RTE quail eggs, there is no risk due to the growth of C. perfringens in these products at retail markets.