This study is done to evaluate a dry sterilization method of plant pathogens on the citrus during storage. Cold plasma technique based on dielectric barrier discharge (DBD) technology was used for plasma actuating. Citrus was stored both cold (5℃, 90%RH) and ambient (18℃, 50%RH) store and analyzed for 3 weeks. Treatment (N=24) and control samples (N=48) were randomly divided for each group. The specification of the DBD plasma actuator is as follows: input voltage is 130 V, current is 0.3 A, flow rate is 15L/min, actuator operation time is 5 seconds (ON), and break time is 30 minutes (OFF). Concentration of ozone was 1.0~3.7 ppm and nitrogen dioxide was 0.5~2.5 ppm. Sterilized air was circularized by a diaphragm pump through a transparent Teflon pipe connected to the chamber and the actuator. Every 3~4 days, the selected samples were rinsed and then inoculated with potato dextrose agar (PDA) for 5 days. Cell number was counted by hemocytometer. Physical properties such as weight, color, soluble solid contents (SSC) and rigidity of peel were measured and compared during storage. Color and rigidity was measured four spots through equator of fruits.

This study, for the first time, investigated the packaging requirements of in-package dielectric barrier discharge cold plasma treatment (DBD-CPT). The parameters determining packaging requirements include the internal oxygen concentration, headspace volume to sample volume ratio (HSR), direct or indirect treatment, and kind of packaging material. Grape tomato and mixed vegetables, composed of romaine lettuce, red cabbage, carrot with and without the inoculation with Salmonella, were subjected to DBD-CPT at 32.5 kV for 3 min. Increasing the oxygen concentration in the container from 5% to 90% did not influence Salmonella inactivation (p>0.05). Increasing the HSR of air packaging material from 54:1 to 522:1 increased Salmonella inhibition on grape tomato (p<0.05). Higher Salmonella inhibition was found in grape tomatoes in directly treated salads than in indirect-treated salads (p<0.05). The inactivation of indigenous mesophilic aerobic bacteria was exhibited higher when packaged with PE than with PET (p<0.05). Optimal package requirements were determined as HSR of 522:1, direct treatment, and uses of PE as packaging material for the microbial inactivation using in-package cold plasma treatment. DBD-CPT increased the water vapor permeability of all packaging materials (p<0.05), but did not change their tensile properties and transparency (p>0.05). Overall, DBD-CPT was found effective in decontaminating mixed vegetables, prepackaged with commercial packages, without affecting the tensile and optical properties of the packages. Furthermore, the HSR, the electrode-container distance and kind of packaging material were identified as the major packaging requirements affecting the microbial inactivation efficacy of in-packaged cold plasma treatment.

This study was conducted to investigate the effect of cold plasma combined with UV-C irradiation against Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes on lettuce. E. coli O157:H7, S. Typhimurium, and L. monocytogenes, corresponding to approximately 5.82, 5.09, 5.65 log CFU/ g, were inoculated on lettuce, respectively. Then, the lettuce was treated with cold plasma, UV-C and combination (cold plasma + UV-C), respectively. The treated lettuce was stored for 9 days at 4oC for microbiological analysis and sensory evaluation. Cold plasma reduced the populations of E. coli O157:H7, S. Typhimurium, and L. monocytogenes by 0.26, 0.65, and 0.93 log CFU/g, respectively. Each microorganism were reduced by 0.87, 0.88, and 1.14 log CFU/ g after UV-C treatment. And, the combined treatment that was treated by cold plasma after UV-C treatment reduced the populations of inoculated microorganisms by 1.44, 2.70, 1.62 log CFU/g, respectively. The all treatment significantly (p < 0.05) reduced the populations of all inoculated bacteria compared to untreated lettuce. UV-C combined with cold plasma was the most effective for reducing the pathogenic bacteria on lettuce, by showing log-reductions of ≥ 2.0 log CFU/g. All treatment was not significantly different until 6 day storage compared to control group in terms of appearance, texture and overall acceptability. Therefore, the combined treatment will be an effective intervention method to control the bacteria on lettuce.

Effects of dielectric barrier discharge atmospheric cold plasma (DACP) treatment on the inhibition of Salmonella and the storability of grape tomato were investigated. Grape tomatoes, with or without inoculation with a cocktail of three strains of Salmonella (~8 log CFU/g tomato), were packaged in a polyethylene terephthalate commercial clamshell container and cold plasma-treated at 35 kVat 1.1 kHz for 3 min using an DACP treatment system equipped with a pin-type high-voltage electrode. DACP treatment resulted in ~1 log CFU/tomato reduction of Salmonella, irrespectively of the size of container (316, 595vs. 758 cm3), the number of grape tomatoes in the container (3, 7, vs. 11), and the position of the tomato in the container(P > 0.05).Rolling integrated during treatment significantly increased the Salmonella reduction rates to 3.1±0.3 and 3.3±0.8 log CFU/tomato in the single-layer and double-layer configurations of the tomato samples in the container (992 cm3), respectively. Rolling-adopted DACP initially reduced the number of total mesophilic aerobes and yeast and molds in the double layer configuration of tomato samples by 1.3±0.3 and 1.5±0.2 log CFU/tomato, respectively, without altering the color and firmness of the tomatoes. The growth of Salmonella, total aerobes, and yeast and molds on DACP-treated grape tomatoes was effectively prevented during storage at 10 °C. DACP treatment did not influence the tomato color index (a*/b*), firmness, weight loss, pH, total soluble solid content, and lycopene concentration of grape tomatoes at 10 and 25 °C (P> 0.05). DACP treatment holds promise as a post-packaging process for improving microbial safety against Salmonella and storability of fresh grape tomatoes.

비열 처리 기술인 유전체 장벽 방전 저온 플라즈마(dielectric barrier discharge cold plasma, DBD-CP)를 이용하여 양 파 분말에 접종된 Salmonella Enteritidis, Escherichia coli O157:H7, 그리고 Listeria monocytogenes의 저해 효과를 조사 하였다. DBD-CP 처리 조건으로서 DBD-CP 형성 가스는 헬륨이었고, 독립 변인은 처리 전압(4, 5, 6, 7, 8, 그리고 9 kV)과 처리 시간(5, 10, 12, 15, 그리고 20분)이었다. 미생물 저해율과 양파 분말의 표면 온도를 종속 변인으로 하여 DBD-CP 최적화 조건을 확립하였고, 이를 바탕으로 S. Enteritidis 저해율에 대한 예측 모델을 구축하였다. 또한 양파 분말의 입자 크기와 수분활성도(Aw)에 따른 S. Enteritidis 저해 효과를 알아보았다. 또다른 처리 조건으로서 헬륨-물 혼 합 가스를 형성 가스로 사용하여 9 kV에서 5분 동안 주파수(15, 25, 그리고 35 kHz)에 따른 미생물 저해율과 시료 표면 온도에 대한 영향을 관찰하였다. DBD-CP 처리에 의해 양파 분말에 접종된 S. Enteritidis, E. coli O157:H7, 그리고 L. monocytogenes는 각각 ≤2.3 ± 0.1, ≤1.4 ± 0.2, 그리고 ≤0.7 ± 1.2 log CFU/cm 2까지 저해되었고, 시료의 최고 온도는 38.5 ± 1.52℃이었다. 양파 분말에 접종된 S. Enteritidis의 저해율에 대한 DBD-CP 최적 조건은 9 kV와 20분이었고, S. Enteritidis 저해율을 가장 적절하게 예측한 모델은 Fermi’s model (R 2 =0.93)이었다. 수분활성도가 0.4, 0.8인 양파 분말의 S. Enteritidis 저해율은 각각 2.3 ± 0.1, 1.8 ± 0.1 log CFU/cm 2로 유의적인 차이가 없었고(p>0.05), 입자 크기가 0.25, 1.00 cm 2인 양파 분말의 S. Enteritidis 저해율은 각각 2.3 ± 0.1, 1.0 ± 0.5 log CFU/cm 2로 입자의 크기가 작을수록 저해율이 높았다. 헬륨-물 혼합 가스로 DBD-CP 처리시 모든 식중독균에서 주파수가 작을수록 저해율이 증가하였고, 헬륨의 단 독 처리에 비해 미생물 저해율이 유의적으로 증가하였다(p<0.05). 현 연구를 통해 DBD-CP 처리 기술은 분말 식품의 품질 보존 및 미생물 안전성을 향상시키기 위한 살균 방법으로서의 가능성을 보여주었다.

This study was performed to have an effect on control the growth of algae such as "Actinastrum fluviatile" which occurs frequently in the aquaculture tank using by a cold plasma, and it also would be expected to promote the growth of water plants due to active element causing OH radicals in the water. In addition, it was verified on the death rate as 99.9% on the scale protrusion of "Aeromonas hydrophila" as well as E. coli, especially, under extreme conditions more than 100 million pathogenic bacterium in the aqua pet tank, the ornamental fish had to act in a safe and healthy environment at over 98% death rate within 48 hours. It has been proven to give no affect on aerobic bacteria that exist in the filter or soil because there was no residual toxicity in the water tank. As the results, it will help to develop and apply on the sterilization device in other industries as well as aquarium organisms due to adopted energy-saving algorithm and reliability in use.

국내에서 생산되는 벼의 저장안전성 확보를 위한 기초기 반연구로 플라즈마 기술을 이용하여 벼의 저장기간 및 온도에 따른 미생물 생육 및 성분 변화를 관찰하였다. 플라즈마 시스템은 컨테이너형 유전격벽 플라즈마로 공기방전방식을 이용하여 삼광, 청품, 미소미, 팔방미 품종을 0, 10 및 20분간 처리하여 4℃, 25℃에서 2달간 저장하여 실험하였 다. 미생물 생육 변화를 관찰한 결과 저장 초기에는 일반호기성 미생물은 3.46-3.86 log CFU/g, 곰팡이는 2.27-2.86 log CFU/g이 검출되었다. 저장온도 및 기간에 따라 일반호기성 미생물 및 곰팡이의 생육은 증가하였으며, 품종간의 큰 차이는 없었다. 저장한 후의 미생물 분석 결과 플라즈마 처리 군의 미생물이 약 1.50 log CFU/g 적게 생육되었다. 플라즈마 처리한 벼의 수분함량을 측정한 결과 플라즈마 처리에 의한 큰 차이는 관찰되지 않았으나, 저장온도가 올라가면 수분함량이 감소하는 것을 확인하였다. 지방은 플라즈마에 의해 감소하는 경향을 보였으나, 단백질 함량은 플라즈마 및 저장조건에 따른 일관적인 변화는 관찰되지 않았다. 아밀로스 함량의 경우 삼광, 청품, 미소미 품종은 플라즈마에 의한 함량 변화는 관찰되지 않았으나 팔방미는 증가하는 경향을 보였다. 이상의 결과를 종합하여 볼 때 플라즈마에 의해 벼의 저장안전성을 개선할 수 있으며 품질 변화의 최소화를 위하여 저온저장이 효과적이라고 판단된다.

There are many species as bioenergy crops and have different cold sensitivity in each. Cold-tolerant camelina and rapeseed, -sensitive jatropha, were used to investigate the cold stress response. Various physiological parameters such as leaf length, width, electrolyte leakage, stomatal conductance and chlorophyll fluorescence were measured to determine the growth rate treated with cold (2℃) for 5 days. Cold treated jatropha was damaged seriousiy but camelina and rapeseed were withstand. In order to investigate the cold-response on plasma membrane H+-ATPase activity isolated from leaves and roots of camelina, rapeseed and jatropha crops were exposed to cold stress. There were an increase in the activity of leaves and roots plasma membrane in cold-tolerant crops (camelina, rapeseed) while decreased the activity in cold-sensitive crop (jatropha). By western-blot analyses, the protein expression of plasma membrane H+-ATPase isolated from leaves and roots of camelina and rapeseed was increased in the presence of cold stress, but not in jatropha. These results may suggest that increased plasma membrane H+-ATPase of crops are closely related with cold-tolerant.