The Growth of Salmonella enteritidis, Staphylococcus aureus and Escherichia coli on Ready-to-eat Meats under Various Temperature Conditions

다국어 초록 (Multilingual Abstract)

Ready-to-eat products are food products that are not further treated before consumption in such a way that may significantly reduce the microbial load. In recent years, the consumption of this type of food has increased markedly in Korea, becoming an important vehicle of foodborne diseases.
This study analyzed the effect of storage time and storage temperature on pork hock and duck meat using pathogenic strains. Ready-to-eat meats were inoculated with S. enteritidis ATCC 13076, S. aureus ATCC 25923 and E. coli ATCC 9873 strains. The target inoculation level was 2 to 3 log cfu/g. Inoculated and control samples were stored at temperature 5 ℃, 10 ℃, 15 ℃ and 20 ℃ for 9 days, and examined for presence and numbers of pathogens.
The results obtained follows;
1. Chemical component
The results of the proximate composition of pork hock and duck meat; the respective moisture contents were 54.25% and 57.51%; the protein levels, 23.23% and 16.87%; the fat content and ash content, 20.86% and 23.52% and 0.79% and 1.23%.
2. Aerobic colony counts and coliforms
The results revealed a mean log count for of 1.82 and 1.89 log cfu/g for aerobic colony counts and a mean coliforms of 1.30 and 1.03 log cfu/g for both pork hock and duck meat, respectively.
3. Time-temperature simulation
1) The variation of aerobic colony counts for control samples according to the storage temperature showed gradually increase 2, 4, 5, and 6 log cfu/g at 5 ℃, 10 ℃, 15 ℃ and 20 ℃, respectively.
2) The variation of S. enteritidis, S. aureus, E. coli counts for standard strain S. enteritidis ATCC 13076, S. aureus ATCC 25923, E. coli ATCC 9873 which was artificially put into pork hock and duck meat showed gradually increase at 10 ℃, 15 ℃ and 20 ℃. At the lowest temperature tested(5 ℃), bacterial growth was stagnant.
Considering the results of our experiment, it seemed that the final microbial count was high at the assessed temperature during the storage period due to the high level of microbial contamination prior to the experiment. And overall results showed that held at 5 ℃, there was no apparent growth of S. enteritidis, S. aureus, or E. coli in any of the ready-to-eat meats. The most easily controlled factor is the storage temperature at retail stores. These results suggest that a temperature of less than 5 ℃ is critical control point for ready-to-eat meats retail establishments to prevent the growth of S. enteritidis, S. aureus and E. coli.

국문 초록 (Abstract)

본 연구에서는 시중 유통되고 있는 즉석조리식품 고기류를 대상으로 2008년 1월부터 5월까지 용인지역의 대형할인매장에서 판매되고 있는 족발과 오리고기를 중심으로 제품의 Salmonella enteritidis, Staphylococcus aureus, Escherichia coli 균주를 이용하여 보관온도와 시간에 따른 균수의 변화를 실험한 결과 다음과 같이 나타났다.
1. 일반성분분석
족발과 오리고기의 일반성분 분석결과; 수분함량은 54.25%, 57.51%; 조단백질은 23.23%와 16.87%; 조지방은 20.86%와 23.52%로 나타났으며 조회분은 0.79%와 1.23%의 결과를 나타내었다.
2. 일반세균수 및 대장균군수
일반세균은 족발에서 평균 1.82 log cfu/g, 오리고기에서는 1.89 log cfu/g으로 나타났으며, 대장균군은 족발에서 1.30 log cfu/g, 오리고기에서 1.03 log cfu/g으로 나타났다.
3. 시간-온도 시뮬레이션
1) 유통중인 족발과 오리고기의 보관온도에 따른 일반세균수의 변화는 5 ℃, 10 ℃, 15 ℃와 20 ℃에서 각각 2, 4, 5, 그리고 6 log cfu/g의 성장을 나타냈다.
2) 표준균주 S. enteritidis ATCC 13076, S. aureus ATCC 25923, E. coli ATCC 9873을 인위적으로 넣어 만든 족발과 오리고기의 보관온도별 균수 변화는 20 ℃, 15 ℃, 10 ℃ 순으로 균의 성장을 나타내었고, 5 ℃에서는 균의 성장이 일어나지 않고 생존하는 양상을 나타냈다.
본 연구 결과를 근거로 할 때, 보관온도 및 보관기간에 따른 최종 미생물수가 높은 것으로 나타났다. 또한 5 ℃에서는 균의 성장이 나타나지 않았으므로 즉석조리식품 고기류의 미생물학적 안전성을 유지하기 위해서는 5 ℃ 이하의 온도관리가 요구된다.

목차 (Table of Contents)

• Ⅰ. Introduction = 1
• Ⅱ. Materials and Methods = 7
• 1. Sample collection. = 7
• 2. Proximate composition analysis = 7
• 3. Aerobic colony counts and coliforms = 8
• 4. Time-temperature simulation = 8
• 1) Study design = 8
• 2) Inoculum preparation = 9
• 3) Inoculation and packaging of the ready to eat meat = 9
• 4) Microbiological examination = 10
• 5) pH analysis of the stored meat = 12
• 5. Statistical analysis = 12
• Ⅲ. Results = 13
• 1. Chemical composition = 13
• 2. Aerobic colony counts and coliforms = 14
• 3. Time-temperature simulation = 16
• 1) Microbial populations of controls = 16
• 2) Growth of S. enteritidis = 19
• 3) Growth of S. aureus = 22
• 4) Growth of E. coli = 26
• 5) Change of pH on ready-to-eat meats = 30
• Ⅳ. Discussion = 34
• Ⅴ. Reference = 46
• ABSTRACT = 58
• Appendix = 62