초록 ▼

Ⅳ. 연구개발결과
채소류 4종의 일반 세균수 수준을 비교한 결과 계절과 관계없이 상추의 일반 세균수 수준이 가장 높았고, 토마토의 일반 세균수는 가장 낮았다. 대장균군도 상추가 가장 높은 오염도를 나타내었다. 상추, 깻잎, 오이, 토마토의 일반 세균수에서 유기농, 무농약, 일반 농법에 따른 유의한 차이가 거의 없었다. 또한 각 작물의 대장균군에서도 작물재배 농법에 따른 유의한 차이를 볼 수 없었다. 본 실험에 사용된 채소에서 Salmonella spp., E. coli O157:H7, L. monocytogenes 등은 전혀

Ⅳ. 연구개발결과
채소류 4종의 일반 세균수 수준을 비교한 결과 계절과 관계없이 상추의 일반 세균수 수준이 가장 높았고, 토마토의 일반 세균수는 가장 낮았다. 대장균군도 상추가 가장 높은 오염도를 나타내었다. 상추, 깻잎, 오이, 토마토의 일반 세균수에서 유기농, 무농약, 일반 농법에 따른 유의한 차이가 거의 없었다. 또한 각 작물의 대장균군에서도 작물재배 농법에 따른 유의한 차이를 볼 수 없었다. 본 실험에 사용된 채소에서 Salmonella spp., E. coli O157:H7, L. monocytogenes 등은 전혀 검출되지 않았다. 대장균은 상추(유기농, 무농약, 일반), 오이(무농약), 깻잎(일반)에서 검출되었으며 유기농, 무농약, 일반 농산물에서 골고루 확인되었다. B. cereus는 총 시료 중 깻잎, 상추, 토마토, 오이에서 골고루 검출되었고 오염도에서 각 작물에서 재배농법에 따른 큰 차이는 보이지 않았다. 계절별 차이를 살펴보면 일반 세균수, 대장균군, 대장균은 다른 계절보다 여름에 높은 오염도를 나타내었다. S. thyphimurium, L. monocytogenes, S. aureus은 대두박에서 biofilm 형성이 잘 되었고, 친환경 농자재에서 외부오염 시 유해미생물 증식가능성이 있으므로 위생관리를 철저해야 한다. 일반농산물 및 유기농산물의 부패미생물 균총 비교 및 오염도 조사에서 일반농산물과 유기농산물에서 발견된 균종은 약간의 차이는 있었으나 유사한 종이 관찰되어 관행 및 유기농법시 신선 농산물에 오염된 부패 미생물의 차이는 관찰되지 않았다. 자연항균제 탐색 실험 결과 carvacrol, thymol, eugenol을 처리하였을 때 위해 및 부패미생물의 G+균과 G-균 모두에서 높은 항균 효과를 나타냈다. 자연항균제의 항균력 평가 시 부패미생물 간의 항균 물질의 항균력 차이가 나타났고 신선 농산물에 식물성 항균 오일의 살균처리 시 상추에 oregano처리 후 7일 동안 냉장 보관 하였을 때 가장 높은 항균효과가 관찰되었다. 신선 농산물에 오염된 유해미생물에 대한 항균물질과 에어로졸의 결합처리 실험 결과 전체적으로 유해미생물에 대한 저해 효과가 낮은 것으로 관찰하였고 항균효과가 높았던 식물성 항균 오일 lemongrass과 CO2 100% 기체조절포장법을 결합처리 한 후 21일 동안 냉장 보관 하였을 때 부패미생물의 성장이 관찰되지 않았다. 신선 농산물의 종류에 따라 기체조절포장 시 효과에 차이가 관찰되었고 뿌리채소인 연근을 CO2 100% 기체조절포장을 하였을 때 품질이 21일 동안 유지됨을 관찰하였다. 연근을 ascorbic acid와 chamomile를 결합처리 후 CO2 100% 기체조절포장을 하였을 때 품질이 21일 동안 유지됨을 확인하였다.

Abstract ▼

The majority of foodborne outbreaks arise from bacterial pathogens that may contaminate via several routes prior to harvest. Potential preharvest sources of contaminating microorganisms include soil, feces, irrigation water, dusts, or inadequately composted manure. Manure always contains microorgani

The majority of foodborne outbreaks arise from bacterial pathogens that may contaminate via several routes prior to harvest. Potential preharvest sources of contaminating microorganisms include soil, feces, irrigation water, dusts, or inadequately composted manure. Manure always contains microorganisms originating from feces. Animal manure is a commonly used fertilizer in organic vegetable and fruit production in Korea as well as in USA. In this study, total aerobic bacteria, coliforms, Escherichia coli , foodborne pathogens such as Salmonella spp., Escherichia coli O157:H7, Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus were monitored to get the microbial contamination levels of fresh vegetables (organic, pesticide-free, and conventional produce) including lettuce, perilla leaf, cucumber, and tomato in Korea. The total aerobic bacteria and coliforms counts in organic vegetables, pesticide-free vegetables, conventional vegetables were not significantly different (p<0.05). E. coli was detected in organic lettuce, pesticide-free lettuce, conventional lettuce. B. cereus contamination was found in organic, pesticide-free, conventional vegetables. Salmonella spp., E. coli O157:H7, and L. monocytogenes were not detected from any vegetable samples. Salmonella spp. and L. monocytogenes survived in environmental friendly agricultural materials. The microbial contamination levels determined in the present study may be able to be used as the fundamental data to execute microbial risk assessment of fresh vegetables. This study will provide useful and practical guidelines to applicators of soil in deciding appropriate handling and time frames for land application of livestock manure compost for sustainable agriculture. Results from these studies provide useful information in identifying environmental friendly agricultural materials handling practices to reduce the risk of S. enterica, E. coli O157:H7, L. monocytogenes, and S. aureus transmission to fresh produce. The purpose of this study was to investigate growth characteristics and biofilm formation of spoilage bacteria isolated from organic or conventional fresh produce and contamination levels and isolation of spoilage bacteria. And to develop effective sanitizing method in fresh produce using essential oils (EOs) combined with aerosolization and Modified Atmosphere Packaging (MAP) against pathogens or spoilage bacteria. When growth characteristics and biofilm formation of spoilage bacteria was evaluated, the number of spoilage bacteria present when stored at 35°C was significantly greater than when stored at lower temperatures, and maximum population size was achieved after 10h. Bacillus pumilus, Dickeya zeae, Pectobacterium carotovorum subsp. Carotovorum Pcc21, and Bacillus pumilus (RDA-R) did not grow at the storage temperature of 5°C. The biofilm formation by Clavibacter michiganensis, Acinetobacter calcoaceticus, and A. calcoaceticus (RDA-R) are higher than other spoilage bacteria. Biofilm formation showed low correlation between hydrophobicity, and no significant correlation with colony spreading. When the isolation and identification of spoilage bacteria on organic and conventional fresh produce were tested, population of total aerobic bacteria on conventional perilla leaf, cabbage, and romaine lettuce were 7.59, 7.01, and 5.84 log10 CFU/g, and populations of total aerobic bacteria were 6.72, 6.15, and 5.85 log10 CFU/g for organic perilla leaf, cabbage, and romaine lettuce, respectively. Major spoilage bacteria of organic and conventional fresh produces were similar however their levels were little different. As the next study, inhibitory effect of EOs against pathogens and spoilage bacteria were evaluated. Carvacrol, thymol, and eugenol showed strong inhibitory effects compared to those of the other antimicrobial substances, and their average minimum inhibitory concentration (MIC) values against 15 spoilage bacteria were 167, 648, and 168 mg/ml, respectively. And two combinations (carvacrol + thymol, and carvacrol + thymol + eugenol) showed the strongest inhibitory effects against bacteria in fresh vegetables among all treatments. Among EOs, thyme-1, thyme-2 and tea tree-2 oils demonstrated the strongest antibacterial effect against 18 strains of pathogens. Thyme-1 oil showed the strongest antibacterial effect against spoilage bacteria. The dipping treatment results showed that oregano-2 oil was the most effective at maintaining reduced levels of total mesophilic microorganisms in lettuce and radish sprouts compared with control, although it affected the quality of both vegetables after treatment. When EOs was applied on fresh produce as aerosol, aerosolization treatment of EOs showed weak inhibitory effectiveness in controlling various pathogens. When investigate the inhibitory effects of various MAP gas composition against spoilage bacteria and combined effects of EOs in vapor phase and MAP were evaluated, the MAP results showed that 100% CO₂ gas packaging reduced significantly levels of total mesophilic microorganisms on cabbage and radish sprouts, and their reduction level was 1.55 and 2.26 log10 CFU/g compared to control after 21 days of storage. combined effects of EOs in vapor phase and MAP (100% CO₂) showed that lemongrass-2 oil with 20 discs showed complete inactivation by < 1.0 log10 CFU/g after 14 days of storage. Finally, the effect of various concentrations (1% ascorbic acid (AA), 0.5% chamomile (CM), 1% AA + 0.5% CM) of anti-browning treatment and heat treatment (45 sec/55oC) combined with packaging in various gas composition of MAP on the quality and microbiological characteristics of fresh-cut lotus root was evaluated. The quality characteristics (color, weight loss, texture, pH, polyphenoloxidase activity and total phenol content) of AA + CM dipped sample combined with 100% CO₂ packaging were maintained significantly higher quality than other samples. As a results, optimum working condition of dipping into anti-browning treatment (AA + CM), 100% CO₂ packaging could be a good method to extend the shelf life of fresh-cut lotus root for 21 days at 5oC. From the results of this study, the combination of EOs and MAP could be applied for sanitizing or distribution and storage process, respectively, in order to improve the safety of organic or conventional fresh produce and quality following treatments. These results could be used for developing new commercial and industrial sanitizing or storage methods of fresh products.