초록 ▼

Ⅳ. 연구개발결과
제 1세부(3장 1절)에서는 약 2,000주의 분리균주 중 항균활성이 있는 박테리오신 생성균주 2주(HD15, DC8)를 확보하고, 박테리오신을 분리, 정제하여 특성을 분석하였다. 바실러스 테퀄엔시스 HD15의 박테리오신을 신선육 포장재(포장필름, 흡습용 패드)에 적용하여 분석한 결과, 저장초기에 식중독균(바실러스 세레우스, 리스테리아 모노사이토제네스)을 제어효과가 있는 것으로 나타났다. 제 4세부(3장 2절)에서는 식중독균(장출혈성대장균, 살모넬라균, 바실러스 세레우스)을 제어하는 박테리오파지 약 110여주

Ⅳ. 연구개발결과
제 1세부(3장 1절)에서는 약 2,000주의 분리균주 중 항균활성이 있는 박테리오신 생성균주 2주(HD15, DC8)를 확보하고, 박테리오신을 분리, 정제하여 특성을 분석하였다. 바실러스 테퀄엔시스 HD15의 박테리오신을 신선육 포장재(포장필름, 흡습용 패드)에 적용하여 분석한 결과, 저장초기에 식중독균(바실러스 세레우스, 리스테리아 모노사이토제네스)을 제어효과가 있는 것으로 나타났다. 제 4세부(3장 2절)에서는 식중독균(장출혈성대장균, 살모넬라균, 바실러스 세레우스)을 제어하는 박테리오파지 약 110여주를 분리 확보하였다. 이 중 장출혈성대장균을 저해 가능한 박테리오파지로 항균포장재를 제작하였다. 제 1협동(3장 3절)에서는 신선육의 품질 변화를 최소화 하면서 효과적으로 미생물을 제어하는 모델로 포장재 내부 발생 유전체 장벽 플라즈마를 개발하여 원형을 제작하였다. 플라즈마를 10여 분 처리할 경우 약 2～3 log의 식중독균을 제어하는 효과를 나타내었다. 박테리오신, 파지와 저온플라즈마를 복합처리할 경우 박테리오신과 파지의 단독처리군에 비해 식중독균 저감효과가 상승하였다. 제 2협동(3장 4절)에서는 UV, UV-TiO₂, 저온플라즈마(Jet plasma)에 의한 바이러스 저감효과를 분석한 결과, 저온플라즈마가 다른 기술에 비해 신선육 표면에 접종된 바이러스를 더 잘 제어하는 것으로 나타났다.

Abstract ▼

○ Development and application of non-thermal process for controlling microorganisms in fresh meat by cold plasma, bacteriocin and bacteriophage
This study was performed to select a bacteriocin-producing microorganism. A total of 2,000 bacterial species were isolated from various sources including

○ Development and application of non-thermal process for controlling microorganisms in fresh meat by cold plasma, bacteriocin and bacteriophage
This study was performed to select a bacteriocin-producing microorganism. A total of 2,000 bacterial species were isolated from various sources including cattle feces, Kimchi, milk, Cheonggukjang and meat products. In order to isolate a bacteriocin-producing strain, the diameter of the clear zone on MRS agar plate was measured. Isolates showed antibacterial activity against food-borne pathogenic bacteria including Listeria monocytogenes and/or Bacillus cereus. Finally, the strains HD15 and DC8 were selected for its superior antibacterial activity. The isolate was identified as Bacillus tequilensis by 16S ribosomal RNA analysis and designated as B. tequilensis HD15. Bacterial growth, in tryptic soy broth at 37℃, reached stationary phase after 36 h of incubation, and the optimum activity of bacteriocin showed at 60 h of incubation. The bacteriocin was purified by 0∼80% ammonium sulfate precipitation, DEAE Sepharose FF anion-exchange chromatography, and Sephacryl S-200HR gel filtration chromatography. Specific activity of the bacteriocin was determined to be 413.4 AU/mg of protein and its yield was 26.2% of the total activity of crude extracts. The molecular weight of the purified bacteriocin was estimated to be 3.6 kDa by Tricine SDS-PAGE analysis. The bacteriocin was proteinaceous and sensitive to heat and proteolytic enzyme treatment. The other isolate was identified as Enterococcus faecium by 16S ribosomal RNA analysis and designated as E. faecium DC8. Bacterial growth in the optimal medium at 37℃ reached stationary phase after 24 h of incubation and the antimicrobial compound showed optimum activity at 72 h. Antimicrobial compound was purified by 30∼60% ammonium sulfate precipitation, CM Sepharose CL-6B cation exchange chromatography and Sephacryl S-200HR gel filtration chromatography. The antimicrobial compound was proteinaceous and sensitive to heat and proteolytic enzyme treatment.
The aims of another study were to isolate and characterize the bacteriophages against Escherichia coli O157:H7, Salmonella species, and other foodborne bacteria from various sources including foods and to develop the antimicrobial package for the inhibition of foodborne pathogens on beef, pork, and chicken meat by the treatment of single bacteriophage. Total 14 Escherichia coli O157:H7 bacteriophages and 15 Salmonella spp. bacteriophages and 2 B. cereus bacteriophages were purchased from Bacteriophage bank in Hankuk Foreign Language University and amercian type culture collection. From fermented foods and various sources, 87 bacteriophage strains against E. coli O157:H7, Salmonella Enteritidis, Salmonella Typhimurium, Bacillus cereus were isolated. For the characterization of each strain, plague size and virulence factor profiles were examined by plague assay and PCR, respectively. Transmission electron microscopy was also performed. For each E. coli bacteriophage DNA, the detection rate of eae, stx2, estI , astA, and ial was 100%, 69.6%, 13.0%, 13.0%, 8.7%, respectively. stx2+eae, eae+astA, eae, stx2+eae+estI , eae+estI , stx2+eae+ial , and eae+ial were observed in bacteriophages isolated from sewage. As several plasmid-carrying virulence factors (estI , astA, and ial) were found in E. coli O157:H7 bacteriophages obtained from sewage and stools, the microbial safety of bacteriophages should be investigated in further study. The highly lytic bacteriophage BPECO19 strain was selected and used to inhibit E. coli O157:H7 in artificially contaminated meat samples. Bacteriophage BPECO19 significantly reduced E. coli O157:H7 bacterial load in vitro in a multiplicity of infection (MOI)-dependent manner. This strain completely inhibited E. coli O157:H7 bacterial load in beef and pork at 4 and 72 h, respectively. In chicken meat, a significant reduction of E. coli O157:H7 was observed at 4 h. Similar pattern was confirmed that the application of antimicrobial package could inhibit foodborne pathogens effectively in fresh meats. In conclusion, the direct treatment of single bacteriophage and bacteriophage-applied antimicrobial package were effective methods to control foodborne pathogens in fresh meat.
The atmospheric pressure plasma (APP) jet, encapsulated dielectric barrier discharge (DBD) plasma, and flexible thin-layer DBD plasma were newly developed and pathogen-inactivation efficiency of these plasma systems was also investigated. The results showed that the flexible thin-layer DBD plasma had higher bactericidal effect with minimum quality changes compared to the other plasma systems. For these reasons, the effect of a flexible thin-layer DBD plasma system on microbial inactivation of seal-packed raw chicken, pork and beef was tested. The microbial-load reductions of Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella Typhimurium were 3.74, 3.11, and 2.77 log CFU/g in raw chicken-breast, 2.04, 2.54, and 2.68 log CFU/g in pork butt, and 1.90, 2.57, and 2.58 log CFU/g in beef-loin, respectively after 10 min of treatment. The quality changes in raw meats after the flexible thin-layer DBD plasma treatment were also investigated. Colorimetric analysis showed that the thin-layer DBD plasma significantly affect the a*-values (redness) of chicken-breast and pork-butt after 5 min of treatment time while beef loin after 7.5 min of treatment time. Thin-layer DBD plasma treatment also significantly influenced the lipid oxidation in pork butt and beef loin only after 10 min of exposure. The sensory parameters of treated and non-treated raw meat samples were comparable except for flavor and off-flavor, which were negatively influenced by the plasma treatment. The Ames test revealed that none of samples showed mutagenic, and there were no indications of plasma treatment in raw meats. These results proposed that the newly developed thin-layer DBD plasma system can be applied to inactivate foodborne pathogens and minor quality deterioration can be prevented by combination with hurdle technology.
The consumption of meat products has been increasing in many countries. According to the increases in meat consumption, the safety assurance problem of meat products has become the important matter nowadays. Among enteric viruses, norovirus and hepatitis A virus (HAV) are the leading causes involved in outbreaks related to food. The objective of another study was to investigate the survival of norovirus surrogate, (murine norovirus (MNV)) and HAV on diverse food-contact surfaces and fresh meats during storage as well as to study the UV, UV-TiO₂, and Plasma jets effects against foodborne virus on three fresh meats (chicken, pork, and beef). On the food-contact surfaces, the reductions of MNV and HAV were at maximum 2.28, and 2.30 log₁₀ PFU/coupon on stainless steel, while at minimum 1.29, and 1.44 log₁₀ PFU/coupon on wood, respectively. On the fresh meats, there were no (p > 0.05) statistically significant differences of MNV and HAV titers. With the treatment of 3600 ㎽*s/cm² of UV dose, MNV was reduced by 1.12, 1.46 and 1.04 log₁₀ PFU/ml on chicken, pork and beef, respectively, while HAV was reduced by 1.17, 1.22 and 1.05 log₁₀ PFU/ml. After treatment of 10~300 sec of Plasma jet, the reductions of MNV-1 (initial inoculums of 10⁷ PFU/mL) of were > 3 log₁₀ PFU/coupon on six types of food contact surfaces. After treatment of 5~20 min of APP jet, the reductions of MNV-1 (initial inoculums of 10⁷ PFU/mL) of were > 2 log₁₀ PFU/mL on three meats. There was no significant differences (p > 0.05) in L (lightness), a* (redness+, greenness˗), and b* (yellowness+, blueness˗) values until 5 min. Although the TBARS (thiobarbituric acid reactive substance) values stepwise increased by longer duration of APP jet, these TBARS values were below the 1.0 mg MA/kg (as an indicator of rancidity). The results in the current study indicate that the 5 min of Plasma jets showed that > 99% reduction (2 log10 PFU/mL) of MNV-1 without concomitant changes in quality could possibly be used in fresh meat production, processing, and distribution processes to enhance fresh meat safety.