본 연구는 가공치즈에서 Staphylococcus aureus의 생장 을 예측하기 위한 수학적 모델을 개발하였다. 모짜렐라 슬라이스 치즈와 체다 슬라이스 치즈에 S. aureus 혼합균액 (ATCC13565, ATCC14458, ATCC23235, ATCC27664, NCCP10826) 0.1 ml (log CFU/g)을 접종한 후 4oC (1440 h), 15oC (288 h), 25oC (72 h), and 30oC (48 h)에 저장하면서 총 세균 수와 S. aureus 세균 수를 tryptic soy agar와 mannitol salt agar를 이용해 각각 확인하였다. S. aureus의 세균 수 를 Baranyi model로 분석하여 생장률(μmax; log CFU·g−1·h−1), 유도기(LPD; h), 초기 세균수(log CFU/g), 최대 생장 세균 수(log CFU/g)를 계산함으로써 1차 모델을 개발하였다. 또 한 저장온도와 S. aureus의 μmax, LPD의 관계를 분석하기 위해 square root model과 exponential decay model을 이용 하였고 이를 통해 2차모델을 개발하였으며 개발된 모델의 평균제곱근 편차(RMSE)를 계산하여 적합성을 검증하였다. 4oC에서는 모든 가공치즈에서 황색포도상구균의 생장이 관찰되지 않았으나 15oC, 25oC, 30oC에서는 모짜렐라 슬라이스와 체다 슬라이스 치즈에서 황색포도상구균이 생장 하였으며(R² = 0.785-0.996) 저장온도가 높아짐에 따라 생장률은 증가한 반면 유도기는 감소하였다(R² = 0.879-0.999). 또한 개발된 모델의 RMSE 값은 0.3500-0.5344로 적합하였다. 따라서 본 연구결과는 가공치즈에서 황색포도상구균의 생장 예측에 유용하게 사용될 것이다.

This study developed predictive models for the kinetic behavior of Staphylococcus aureus on processed cheeses. Mozzarella slice cheese and cheddar slice cheese were inoculated with 0.1 ml of a S. aureus strain mixture (ATCC13565, ATCC14458, ATCC23235, ATCC27664, and NCCP10826). The inoculated samples were then stored at 4oC (1440 h), 15oC (288 h), 25oC (72 h), and 30oC (48 h), and the growth of all bacteria and of S. aureus were enumerated on tryptic soy agar and mannitol salt agar, respectively. The Baranyi model was fitted to the growth data of S. aureus to calculate growth rate (μmax; log CFU·g−1·h−1), lag phase duration (LPD; h), lower asymptote (log CFU/ g), and upper asymptote (log CFU/g). The growth parameters were further analyzed using the square root model as a function of temperature. The model performance was validated with observed data, and the root mean square error (RMSE) was calculated. At 4oC, S. aureus cell growth was not observed on either processed cheese, but S. aureus growth on the mozzarella and cheddar cheeses was observed at 15oC, 25oC, and 30oC. The μmax values increased, but LPD values decreased as storage temperature increased. In addition, the developed models showed acceptable performance (RMSE = 0.3500-0.5344). This result indicates that the developed kinetic model should be useful in describing the growth pattern of S. aureus in processed cheeses.

ABSTRACT
 Introduction
 Materials and Methods
  Inoculum preparation
  Sample preparation and inoculation
  Analyses
  Primary model
  Secondary model
  Validation
  Statistical analysis
 Results and Discussion
 요 약
 References

• Kyungmi Kim(Department of Food and Nutrition, Sookmyung Women’s University)
• Heeyoung Lee(Department of Food and Nutrition, Sookmyung Women’s University)
• Jinsan Moon(Veterinary Pharmaceutical Management Division, Animal, Plant and Fisheries Quarantine and Inspection Agency)
• Youngjo Kim(Livestock Products Sanitation Division, Ministry of Food and Drug Safety)
• Eunjeong Heo(Food Microbiology Division, Ministry of Food and Drug Safety)
• Hyunjung Park(Agro-Livestock and Fishery Products Policy Division, Ministry of Food and Drug Safety)
• Yohan Yoon(Department of Food and Nutrition, Sookmyung Women’s University) Correspondence to