Combined treatment of bacteriophages, UV-C light, and lauric arginate (LAE) to inhibit listeria monocytogenes on chicken breast tissue

국문 초록 (Abstract)

현재 증가하는 치킨소비로 인해 L. monocytogenes의Listeriosis 발병에 대한 우려가 높아지고 있다. 농촌경제연구원의 예측 정보에 따르면 2005년부터 돼지, 계란, 닭 순으로 소비가 증가하고 있을 뿐만 아니라 소비자 가격측면에서도 가격이 한 해가 지날수록 감소된다. 이는 향후 더욱 큰 치킨의 소비 증가가 예상된다. 이에 대한 방안으로 본 연구에서는 물리적 처리방법인 UV-C light (600, 1200, 1800, and 2400 mJ/cm2), LAE (100, 200 and 400 mg/kg)와 생물학제제인 Listeria Bacteriophages를 이용하여 닭가슴살의 품질 손상 없이 Listeria monocytogenes의 살균효과를 극대화시키고자 한다. UV-C의 조사량과 LAE의 농도가 증가할수록 L. monocytogenes가 유의적으로 (p < 0.05) 감소하였고 Bacteriophages 처리의 경우 1일 경과 후 L. monocytogenes가 유의적으로 감소하였다(p < 0.05). 이에 따라 UV-C light (600, 1200, 1800, and 2400 mJ/cm2)와 bacteriophages로 병용 처리된 닭가슴살은 각각 1.48, 1.66, 1.74, 2.04 log CFU/g 감소하였다. LAE (100, 200, and 400 mg/kg)과 bacteriophages로 처리된 닭가슴살의 L. monocytogenes는 각각 1.24, 1.45, 1.96 log CFU/g 감소하였다. 두 종류의 병용처리된 닭가슴살을 4℃에서 3일 동안 저장 후 pH, TBARS, 색차를 측정한 결과, 대조군에 비해 유의적 차이가 없었다(p < 0.05). 그러나 외관을 고려한다면 UV 1,800 mJ/cm2와 bacteriophages,200 ppm LAE와 bacteriophages의 병용처리 조건이 닭가슴살의 품질을 유지하면서 L. monocytogenes를 저감화시키는데 효과적이라고 판단된다. 본 연구결과는 닭고기의 미생물학적 안전성 확보기술 개발에 기여할 것이다.

다국어 초록 (Multilingual Abstract)

The inhibitory effect of a commercial bacteriophage preparation (ListShield) on Listeria monocytogenes, alone or in combination with treatment with lauric arginate ethyl ester (LAE), Ultraviolet-C, was studied using artificially inoculated fresh chicken breast tissue. A mixture of three L. monocytogenes strains (ATCC 19113, ATCC 19115, and ATCC 13932) was inoculated in fresh chicken breast tissue at approximately 4.5 log CFU/g, followed by treatment with UV-C radiation at 260 nm (four dose 600, 1200, 1800, and 2400 mJ/cm2) and/or bacteriophage preparation Listshield. In case of LAE treatment, LAE (100, 200, and 400 mg/kg) was sprayed and/or sprayed bacteriophage preparation Listshield. Tissues samples were analyzed after 5 min, followed by storage at 4°C for 1, 2, and 3 days. The L. monocytogenes with 600-2400 mJ/cm2 of UV-C maximally reduced by 1.23, 1.47, 1.53, and 1.58 log CFU/g, respectively, compared to the untreated control samples. The counts of these bacteria were significantly difference (p < 0.05) reduced by as stepwise increasing of UV-C dosage. After a single round of treatment with bacteriophages, about 0.56, 0.84, 0.46, and 0.10 log CFU/g reduction was observed after day 0, 1, 2, and 3 days, respectively, compared to the control samples. Significant differences were noted between the treated and control samples (p < 0.05) at 0, 1, and 2 days. After combined treatment with UV-C and bacteriophage, the L. monocytogenes was reduced more significantly by 1.48, 1.66, 1.74, and 2.04 log CFU/g, at 0 day (1-3 h) respectively. In case of LAE treatment, the L. monocytogenes with 100, 200, and 400 mg/kg of LAE were reduced by 0.45, 0.69, and 1.15 log CFU/g at 1day respectively, compared to control samples. After combined treatment with bacteriophages and LAE (100, 200, and 400 mg/kg), the L. monocytogenes count was reduced more significantly by 1.24, 1.45, and 1.96 at 1 day respectively. Following 3 days of treatment, the viable bacterial count of samples of combined treatment with bacteriophages and UV-C irradiation gradually increased to approximately 4.0 log CFU/g regardless of all the UV doses. Also, in the combined LAE and Phages treated samples, reached to approximately 4.5 log CFU/g regardless of all concentrations of LAE. However, no significant difference was observed in the surface color, pH, TBARS content, and visual appearance of the treated and control samples during the 3 days post treatment. Thus, a commercial bacteriophage preparation can be very effective in reducing L. monocytogenes load in chicken fillets, either alone or in combination with UV-C light and LAE treatment.

목차 (Table of Contents)

• Abstract i
• List of Tables vi
• List of Figures viii
• 1. Introduction 1
• 2. Materials and Methods 4
• 2.1 Bacterial strains 4
• 2.2 Bacteriophage preparation & TEM examination 5
• 2.3 Inoculation of chicken breasts 7
• 2.4 Treatment with physical, chemical, and biological agent, alone or in combination 7
• 2.4.1 Exposure to UV-C surface irradiation and Bacteriophages 7
• 2.4.2 LAE and Bacteriophage treatment 8
• 2.5 Microbiological analyses 9
• 2.6 Color and pH measurement 10
• 2.7 2-thiobarbituric acid reactive substances evaluation 11
• 2.8 Visual appearance evaluation 12
• 2.9 Statistical analyses 12
• 3. Results and Discussion 13
• 3.1 Reduction of Listeria monocytogenes treated with UV-C and Bacteriophages on chicken breasts 13
• 3.2 Reduction of Listeria monocytogenes treated with LAE and Bacteriophages on chicken breasts 18
• 3.3 Microbial analysis of chicken breasts after treatment with UV-C and Bacteriophages during storage 21
• 3.3.1 Storage at 4C after single treatment of the UV-C on chicken breasts 21
• 3.3.2 Storage at 4C after single treatment of Bacteriophages on chicken breasts 22
• 3.3.3 Storage at 4C after single treatment of LAE on chicken breasts 23
• 3.3.4 Storage at 4C after combined treatment of the UV-C and Bacteriophages on chicken breasts 24
• 3.3.5 Storage at 4C after combined treatment of the LAE and Bacteriophages on chicken breasts 25
• 3.4 Quality evaluation of chicken breasts treated with UV-C and Bacteriophages during storage 25
• 3.4.1 The pH changes on chicken breasts during storage 25
• 3.4.2 The TBA changes on chicken breasts during storage 27
• 3.4.3 The color changes on chicken breasts during storage 29
• 3.4.4 The changes of visual appearance on chicken breasts during storage 31
• 3.5 Quality evaluation of chicken breasts treated with LAE and Bacteriophages during storage 33
• 3.5.1 The pH changes on chicken breasts during storage 33
• 3.5.2 The TBA changes on chicken breasts during storage 35
• 3.5.3 The color changes on chicken breasts during storage 37
• 3.5.4 The changes of visual appearance on chicken breasts during storage 40
• 4. Conclusion 42
• 5. References 43
• 국 문 초 록 49