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pissn 1229-1153 / eissn 2465-9223 J. Food Hyg. Saf. Vol. 32, No. 1, pp. 64~69 (2017) https://doi.org/10.13103/jfhs.2017.32.1.64 Journal of Food Hygiene and Safety Available online at http://www.foodhygiene.or.kr 양상추에인위접종된 Escherichia coli O157:H7, Salmonella Typhimurium 과 Listeria monocytogenes 에대한저온플라즈마와 UV-C 의살균효과 성지영 박미정 권기현 1 오세욱 * 국민대학교자연과학대학식품영양학과, 1 한국식품연구원 Combined Effect of Cold Plasma and UV-C Against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes on Fresh-cut Lettuce Ji-Yeong Seong, Mi-Jung Park, Ki-Hyun Kwon 1, and Se-Wook Oh* Department of Food and Nutrition, Kookmin University 1 Korea Food Research Institute, Gyeonggi-do, Republic of Korea (Received November 1, 2016/Revised November 5, 2016/Accepted November 8, 2016) ABSTRACT - 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 4 o C 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. Key words : fresh-cut lettuce, cold plasma, UV-C irradiation, pathogens, reduction 건강하고편리한삶을추구하는소비자의요구가증가함에따라신선식품의소비가증가하고있으며이에따라신선식품산업역시꾸준히성장하고있다 1,2). 또한신선식품은미국에서발생하는식중독의두번째다빈도발생식품이기때문에신선식품의안전에대한우려도역시증가하고있다 3). 미국 Centers for Disease Control and Prevention (CDC) 는양상추와같은신선식품에의해발병하는식중독이 1998년부터 2008년사이에발생한식중독발생건수중 *Correspondence to: Se-Wook Oh, Department of Food and Nutrition, Kookmin University, Seoul 136-702, Korea Tel: 82-2-910-5778, Fax: 82-2-910-5249 E-mail: swoh@kookmin.ac.kr 22% 에달한다고보고하였다 4). 이는양상추를포함한채소가수확, 가공, 유통그리고소비과정에서 Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes 와같은다양한식중독세균에의해오염될수있기때문이다 5). 양상추를포함한신선편이식품의살균에는차아염소산나트륨과같은염소계소독제가가장널리이용되고있다 6,7). 그러나염소계소독제는유기물질이많을때활성이저하된다고알려져있으며 8), 또한 trihalomethane와같은발암물질을생성할수있다고알려져있다 7,9). 이에대한대안으로다양한비가열살균기술이연구되고있다. 그중, 저온플라즈마 (Cold plasma) 는광자나전자, 양이온과음이온, free radical과같은활성종을생성하여세포의세 64

Reduction of Pathogens on Lettuce by using Cold Plasma and UV-C 65 포막을파괴하기때문에세균에대한살균효과를나타낸다고알려져있으며세균포자, 곰팡이, 그리고 biofilm도효과적으로불활성화시킨다고알려져있다 10-12). 또한 Ultraviolet-C (UV-C, wavelength of 220-300 nm) 도식중독세균을살균하는효과적인비가열기술로알려져있다 13). UV-C는열발생이없어식품의품질에영향을주지않으며, 설치가용이하고사용하기쉬운장점이있다. 살균기작으로는 DNA를직접파괴하거나피리미딘 dimer 를형성하여균을사멸하는것으로알려져있다 14). UV-C 를신선식품살균에활용한다양한논문이보고되고있다 13,15-17). 그러나아직까지비가열살균기술인저온플라즈마와 UV-C를병합하여식중독세균을저해하였다는연구는보고된바없다. 본연구에서는저온플라즈마와 UV-C를단독이나병행처리하여양상추에인위접종된 E. coli O157: H7, S. Typhimurium과 L. monocytogenes에대한저감효과를측정하였다. Materials and Methods 사용균주 E. coli O157:H7 (ATCC 43895, ATCC 35150, ATCC 43894), S. Typhimurium (ATCC 19585, ATCC 6994, ATCC 14028), L. monocytogenes (ATCC 7644, ATCC 19111, ATCC 19115) 는한국미생물자원센터 (Korean Collection for Type Cultures, KCTC) 에서분양받아사용하였다. 모든균주는 tryptic soy broth (Difco, Franklin Lakes, USA) 를사용하여 37 o C에서 24시간배양하였다. 이후 4,000 g로 4 o C 에서 20분간원심분리후, 0.85% saline (8.5 g/l sodium chloride; Sigma-Aldrich Corp., St. Louis, Mo., USA) 으로세척한후각식중독세균의세가지균주를혼합한 culture cocktail을제조하여접종하였다. 여플라즈마발생정도를조절하였다. 식중독세균이접종된양상추를저온플라즈마장치에고르게배치하였다. 양상추의바로아래에플라즈마발생기를위치시켜 30분동안작동시킨뒤양상추를회수하였다. 오존은플라즈마발생기를이용하여, 시간당 3.5 g으로조절하여사용하였다. UV-C 처리 Biosafety hood 안에서 UV-C-emitting lamp (15W, G40T10, Sankyo, Japan) 를이용하여 254 nm 조건에서 30분처리하였다. UV-C 조사선량은 200 µw/m 2 이었다. UV-C와저온플라즈마를이용한병행처리접종한양상추는저온플라즈마와 UV-C를단독처리하였으며, 또한 UV-C를처리한후저온플라즈마를병행처리하였다. 처리후, 양상추를멸균백 (Whirl-pak, 19 30 cm; Nasco, Fort Atkinson, WI, USA) 에넣어 4 o C에서 9일간보관하면서실험에사용하였다. 미생물분석각처리후, 10 g의양상추에 90 ml의멸균한 0.85% saline를첨가하여 stomacher (Laboratory Blender Stomacher 400; Seward, MO, USA) 로 2분간균질화하였다. 그후, 0.85% saline로십진희석한후, 균에따른각각의선택배지에도말하였다. E. coli O157:H7, S. Typhimurium와 L. monocytogenes의선택배지로각각 Eosin methylene blue agar (EMB, Oxoid, Hampshire, UK), xylose-lysine-deoxycholate agar (XLD, Oxoid, Hampshire, UK) 와 Listeria selective supplement (SR0206E, Oxoid, Hampshire, UK) 를첨가한 Listeria selective agar base (OAB, Oxoid, Hampshire, UK) 를사용하였으며, 도말후 37 o C에서 24-48 시간배양하고형성된집락수를계수하였다. 시료준비및균접종실험에사용된양상추는서울소재대형마트에서실험에사용하기직전구매하였다. 10 g의양상추를 biosafety hood 안에서멸균된알루미늄호일위에두고 100 µl의각각의식중독세균을피펫으로샘플전부분에골고루접종하였다. 균이접종된양상추는 hood 안에서 1시간동안실온 (22 ± 2 o C) 에서자연건조하여균이표면에부착되게하였다. E. coli O157:H7, S. Typhimurium, L. monocytogenes는양상추에초기농도가 5.82, 5.09, 5.65 log CFU/g 이되게각각접종하였다. 저온플라즈마처리본실험에는유전체격벽방전방식을사용하는저온플라즈마장치 (DBD, Water link, Korea) 가이용되었으며, 외부에서타이머의조절에의한임의조절방법을사용하 관능검사패널 5명이저온플라즈마와 UV-C 처리에따른양상추의관능적특성을평가하였다. 9점척도법을이용하여외관, 질감, 전체적인수용도평가를실시하였다. 관능검사요원들은각각의시료를항목에따라 1점이매우좋지않음, 9점이매우좋음으로하여검사를실시하였다. 통계처리모든실험은 3개의 sample을 3반복하였다. 미생물수의평균은 log CFU/g 단위로환산하였다. 실험결과는 SAS 프로그램 (version 9.1, SAS Institute, NC, USA) 의 ANOVA 를사용하여통계처리하였으며, 5% 범위 (p < 0.05) 내에서 Duncan s multiple range test를하여통계적유의성을검증하였다.

66 Ji-Yeong Seong, Mi-Jung Park, Ki-Hyun Kwon, and Se-Wook Oh Results and Discussion 양상추에존재하는식중독세균에대한저온플라즈마와 UV-C, 그리고병행처리의항균효과를 Table 1에나타내었다. E. coli O157:H7, S. Typhimurium, L. monocytogenes는양상추에초기농도가 5.82, 5.09, 5.65 log CFU/ g이되게각각접종하였다. 저온플라즈마와 UV-C 단독처리및병행처리후에양상추에존재하는 E. coli O157:H7은각각 0.26, 0.87, 1.44 log CFU/g 수준으로저감되었다. 저온플라즈마를단독처리한양상추는 E. coli O157:H7 저감효과에서유의적차이가없었지만, UV-C 단독처리와저온플라즈마와 UV-C 병행처리는유의적차이 (p < 0.05) 가있었으며병행처리는 UV-C 단독처리보다더큰유의적차이 (p < 0.05) 가있는것으로나타났다. 보관기간중가장마지막날인 9일째에, 저온플라즈마와 UV-C 단독처리및병행처리후에양상추에존재하는 E. coli O157:H7은각각 0.61, 0.89, 1.55 log CFU/g 수준으로저감되었다. 양상추에존재하는 S. Typhimurium는저온플라즈마와 UV-C 단독처리, 그리고병행처리후에각각 4.44, 4.21, 2.39 log CFU/g로측정되었으며, 이는대조구에비해 0.65, 0.88, 2.70 log CFU/g 수준으로감소한결과이었다. E. coli O157:H7와동일한경향으로저온플라즈마를단독으로처리한처리구를제외한다른처리구에서유의적차이 (p < 0.05) 가있는것으로나타났으며, 역시병행처리에서가장큰저감효과를나타내었다. L. monocytogenes도저온플라즈마와 UV-C를병행처리한처리구에서유의적차이 (p < 0.05) 가있게저감되었다. 양상추에존재하는 L. monocytogenes의농도는저온플라즈마와 UV-C 병행처리후에 0.93, 1.14, 1.62 log CFU/g 수준으로저감되었다. 보관후 9일이경과하였을때저온플라즈마를단독으로처리한양상추에존재하는 E. coli O157:H7, S. Typhimurium, L. monocytogenes는대조구에비해각각 0.61, 1.19, 0.57 log CFU/g 수준으로저감되었다. UV를단독으로처리한양상추에서각각의식중독균은 0.89, 1.66, 1.56 log CFU/g 수준으로감소하였다. 이에비하여저온플라즈마와 UV-C를병행처리한양상추에존재하는식중독균은 1.55, 2.39, 2.43 log CFU/g 수준으로저감되어서병행처리의효과가우수함을알수있었다. 세가지균의저감양상을보면, 대체적으로 S. Typhimurium 는 E. coli O157:H7과 L. monocytogenes에비하여저온플라즈마처리에민감한것으로나타났다. 또한, UV-C 처리시에는 S. Typhimurium, L. monocytogenes, E. coli O157: H7 순으로높은저해효과가있는것으로판단되었다. 한편, 저온플라즈마와 UV-C를병행처리시에도 S. Typhimurium, L. monocytogenes, E. coli O157:H7 순으로저해 효과가크게나타났다. 이러한결과는저온플라즈마와 UV-C 에대한민감도가식중독세균에따라다르기때문인것으로생각되었다. 저온플라즈마처리와 UV-C 처리, 그리고병행처리가양상추의품질에미치는영향을 Table 2에나타내었다. 저온플라즈마처리와 UV-C 처리, 그리고병행처리는처리후 1일이경과했을때부터 appearance score가조금하락하였으나, 대조구와비교하였을때유의적차이가나타나지않았다. 처리후 9일이경과하였을때, 대조구에비하여 UV-C 처리와병행처리에서만유의적 (p < 0.05) 차이가존재하였다. 저온플라즈마처리와병행처리직후 texture score가조금하락하였다. 그러나, 대조구와비교하였을때유의적차이가없었고, 처리후 9일이경과하였을때저온플라즈마처리와병행처리에서유의적 (p <0.05) 차이가존재하였다. 이때, texture score 하락은병행처리가저온플라즈마처리보다유의적으로 (p < 0.05) 크게발생하였다. 병행처리후 9일이경과하였을때, 대조구에비하여 overall acceptability가유의적인 (p < 0.05) 차이를보였다. 평가한모든항목에서관능적품질이모든처리구에서 1-3일이경과하였을때유의적으로 (p < 0.05) 하락하지만, 대조구와비교하였을때는유의적차이가없는것으로판단되었다. 대조구에비하여저온플라즈마처리와 UV-C 처리, 그리고병행처리는보관 6일까지양상추의관능적인품질이잘보존되는것으로나타났다. 다른연구자들역시, 식품에존재하는미생물을저해하기위한처리로저온플라즈마와 UV-C를사용하고있다. 먼저, Lavelli 21) 는저온플라즈마를적색치커리에 15분처리했을때, E. coli O157:H7과 L. monocytogenes는각각 0.33 log CFU/cm 2, 1.35 MPN/cm 2 씩저감되었다. 또한, 처리직후, 적색치커리품질에는유의적인차이가없었지만하루보관후에대조구에비하여차이가나타났다고하였다. 이외에도, Lee 18) 등은현미에존재하는 Bacillus cereus, Bacillus subtilis, 그리고 E. coli O157:H7를저감하기위하여 20분동안저온플라즈마를처리했을때, 2.30 log CFU/g 정도저감되었다고하였다. UV-C 처리로 Cheon 19) 등은고추가루에존재하는 E. coli O157:H7과 S. Typhimurium를 20.4 kj/m 2 세기로처리했을때, 0.22, 0.29 log CFU/g수준으로저해되었으며또한 L*, a*, b* 값이대조구에비해유의적인차이가나지않았다고하였다. Martínez-Hernández 16) 등은 UV-C를 1.07, 0.05, 9.26 kj/m 2 의세기로 E. coli, S. Enteritidis, 그리고 L. monocytogenes가접종된브로콜리에처리했을때, 식중독세균이 1 log 씩저해되었다고보고하였다. 그리고 Lim과 Harrison 20) 은토마토표면에 22.3 mj/cm 2 세기의 UV-C를 30 초처리했을때, 토마토에접종한 Salmonella의개체수가 3.22 log 저해되어대조구에비해유의적인차이가있었다고하였다.

Table 1. Effect of cold plasma and UV-C against E. coli O157:H7, S. Typhimurium, L. monocytogenes inoculated on lettuce during storage at 4 o C for 9 days a Pathogens E. coli O157:H7 S. Typhimurium L. monocytogenes Treatment Log CFU/g 0 day 0.5 day 1 day 3 day 6 day 9 day Control 5.82 ± 0.15 Aa 5.82 ± 0.15 Aa 5.83 ± 0.13 Aa 5.81 ± 0.06 Aa 5.67 ± 0.14 Aa 5.66 ± 0.04 Aa plasma 30min 5.82 ± 0.15 Aa 5.57 ± 0.06 Aa 5.14 ± 0.18 Bb 5.06 ± 0.40 Bb 5.09 ± 0.36 Bb 5.05 ± 0.25 Bb UV 30min 5.82 ± 0.15 Aa 4.95 ± 0.15 Bb 4.65 ± 0.10 Cb 4.75 ± 0.60 BCb 4.68 ± 0.27 Cb 4.76 ± 0.32 Bb Plasma after UV b 5.82 ± 0.15 Aa 4.39 ± 0.35 Cb 4.25 ± 0.06 Db 4.25 ± 0.22 Cb 4.14 ± 0.10 Db 4.11 ± 0.31 Cb Control 5.09 ± 0.57 Aa 5.09 ± 0.57 Aa 5.26 ± 0.33 Aa 4.94 ± 0.09 Aa 4.57 ± 0.15 Aa 4.75 ± 0.20 Aa plasma 30min 5.09 ± 0.57 Aa 4.44 ± 0.14 ABb 4.02 ± 0.34 Bbc 4.06 ± 0.51 Bbc 3.64 ± 0.34 Bc 3.57 ± 0.37 Bc UV 30min 5.09 ± 0.57 Aa 4.21 ± 0.32 Bb 3.80 ± 0.25 Bbc 3.35 ± 0.07 Bcd 2.95 ± 0.21 Ccd 3.09 ± 0.12 Bd Plasma after UV 5.09 ± 0.57 Aa 2.39 ± 0.68 Cb 2.18 ± 0.64 Cb 2.28 ± 0.09 Cb 2.40 ± 0.24 Db 2.36 ± 0.09 Cb Control 5.65 ± 0.38 Aa 5.65 ± 0.38 Aa 5.45 ± 0.46 Aa 5.13 ± 0.37 Aa 5.13 ± 0.13 Aa 5.23 ± 0.13 Aa plasma 30min 5.65 ± 0.38 Aa 4.71 ± 0.41 Bb 4.74 ± 0.31 Bb 4.79 ± 0.13 ABb 4.69 ± 0.18 Ab 4.66 ± 0.17 Bb UV 30min 5.65 ± 0.38 Aa 4.51 ± 0.40 BCb 4.41 ± 0.18 BCb 4.36 ± 0.18 BCb 4.01 ± 0.35 Bbc 3.68 ± 0.16 Cc Plasma after UV 5.65 ± 0.38 Aa 4.03 ± 0.11 Cb 3.90 ± 0.27 Cbc 3.88 ± 0.15 Cbc 3.38 ± 0.22 Cc 2.81 ± 0.46 Dd a Means ± standard deviation obtained in two experiments, one of two experiments in duplicated (n = 3). b Treated with cold plasma for 30min after treating with UV-C for 30min. Different capital letters indicate significant differences (p < 0.05) among treatments for each storage time; different lowercase letters indicate significant differences (p < 0.05) among storage times for each treatment. Table 2. Sensory evaluation of lettuce untreated and treated with plasma and UV-C during storage at 4 o C for 9 days a Sensory characteristics Treatment Sensory evaluation of lettuce (9 scale) 0 day 0.5 day 1 day 3 day 6 day 9 day Control 9.00 ± 0.00 Aa 9.00 ± 0.00 Aa 9.00 ± 0.00 Aa 8.60 ± 0.55 Aab 8.00 ± 0.71 Abc 7.80 ± 0.84 Ac Appearance plasma 30min 9.00 ± 0.00 Aa 9.00 ± 0.00 Aa 8.80 ± 0.45 Aab 8.20 ± 0.84 Abc 7.60 ± 0.89 Ac 7.80 ± 0.45 Ac UV 30min 9.00 ± 0.00 Aa 9.00 ± 0.00 Aa 8.80 ± 0.45 Aa 8.40 ± 0.55 Aab 8.00 ± 0.71 Ab 6.80 ± 0.45 Bc Plasma after UV b 9.00 ± 0.00 Aa 9.00 ± 0.00 Aa 8.60 ± 0.55 Aab 8.00 ± 0.71 Abc 7.60 ± 0.89 Ac 6.20 ± 0.45 Bd Control 9.00 ± 0.00 Aa 9.00 ± 0.00 Aa 9.00 ± 0.00 Aa 8.20 ± 0.84 Ab 7.80 ± 0.45 Ab 8.00 ± 0.71 Ab Texture plasma 30min 9.00 ± 0.00 Aa 8.80 ± 0.45 Aa 8.40 ± 0.55 Aa 7.40 ± 0.89 Ab 7.20 ± 0.84 Ab 6.80 ± 0.45 Bb UV 30min 9.00 ± 0.00 Aa 9.00 ± 0.00 Aa 8.80 ± 0.45 Aa 8.00 ± 0.71 Ab 7.80 ± 0.45 Ab 7.80 ± 0.45 Ab Plasma after UV 9.00 ± 0.00 Aa 8.60 ± 0.55 Aa 8.40 ± 0.55 Aa 7.20 ± 0.84 Ab 7.00 ± 1.00 Ab 5.20 ± 0.84 Cc Control 9.00 ± 0.00 Aa 9.00 ± 0.00 Aa 9.00 ± 0.00 Aa 8.40 ± 0.55 Ab 7.80 ± 0.45 Ac 7.60 ± 0.55 Ac Overall acceptability plasma 30min 9.00 ± 0.00 Aa 9.00 ± 0.00 Aa 8.60 ± 0.55 Aa 8.00 ± 0.00 Ab 7.60 ± 0.45 Ab 6.80 ± 0.45 Ac UV 30min 9.00 ± 0.00 Aa 9.00 ± 0.00 Aa 8.80 ± 0.45 Aab 8.20 ± 0.45 Abc 7.80 ± 0.45 Acd 7.40 ± 0.89 Ad Plasma after UV 9.00 ± 0.00 Aa 8.80 ± 0.45 Aa 8.60 ± 0.55 Aab 8.00 ± 0.71 Abc 7.40 ± 0.55 Ac 5.00 ± 0.71 Bd a Means ± standard deviation obtained in two experiments, one of two experiments in duplicated (n = 3). b treated with cold plasma for 30min after treating with UV-C for 30min. Different capital letters indicate significant differences (p < 0.05) among treatments for each storage time; different lowercase letters indicate significant differences (p < 0.05) among storage times for each treatment. Reduction of Pathogens on Lettuce by using Cold Plasma and UV-C 67

68 Ji-Yeong Seong, Mi-Jung Park, Ki-Hyun Kwon, and Se-Wook Oh 저온플라즈마와 UV-C를양상추에존재하는식중독균의저해를위해사용한본실험의식중독균저해정도와관능평가결과는, 여러앞선연구와비교했을때비슷하거나더높은저해효과를나타냈다. 대부분의신선식품에식중독균이최대 10 2 CFU/cm 2 이하로존재하기때문에 22), 최대 2.70 log CFU/g 미만의저감화효과가나타난본실험의연구결과는신선식품에존재하는식중독균을저해하는방법으로서의활용가치가높을것이라판단된다. Conclusion 양상추에인위적으로접종된 E. coli O157:H7, S. Typhimurium과 L. monocytogenes 에대한저온플라즈마, UV- C 단독처리과플라즈마와 UV-C의병행처리저해효과를측정하였다. 저온플라즈마와 UV-C를병행처리하였을때, 양상추에존재하는식중독세균을저해하는효과가가장크게나타났다. 따라서비가열살균기술인저온플라즈마와 UV-C를병행처리하는것은식중독세균의저감기술로활용될수있을것으로생각되었다. Acknowledgments 본결과물은농림축산식품부의재원으로농림수산식품기술기획평가원의고부가가치식품기술개발사업의지원을받아연구되었음 (grant No. 313032-03-3-HD020). 또한, 이논문은 2015년해양수산부재원으로한국해양과학기술진흥원의지원을받아수행된연구임 ( 다소비횟감의위생안전성확보및소비촉진을위한식품위해인자검출기술개발 ). 국문요약 본연구에서는양상추에접종된 E. coli O157:H7, S. Typhimurium과 L. monocytogene에대하여저온플라즈마와 UV-C 단독처리및병행처리효과를측정하였다. E. coli O157:H7, S. Typhimurium, L. monocytogenes는양상추에초기농도가 5.82, 5.09, 5.65 log CFU/g이되도록각각접종하였다. 저온플라즈마와 UV-C를처리된양상추는 4 o C에서 9일간보관하며미생물학적분석과관능평가를실시하였다. 저온플라즈마처리는 E. coli O157:H7, S. Typhimurium, L. monocytogenes의개체수를각각 0.26, 0.65, 0.93 log CFU/g 수준으로감소시켰다. 또한, UV-C 처리시각각 0.87, 0.88, 1.14 log CFU/g 수준으로감소되었다. 또한 UV-C 처리후저온플라즈마를처리한병행처리에서는각각 1.44, 2.70, 1.62 log CFU/g 수준으로감소하였다. 저온플라즈마와 UV-C 단독처리보다는병행처리가좀더효과적으로균을저감하는것으로판단되었다. 관 능평가결과는외관, 질감, 전체적인수용도면에서대조구와비교하였을때, 보관 6일까지유의적인차이가없었다. 따라서저온플라즈마와 UV-C 병행처리는양상추에존재하는균을저감하기위한효과적인기술로활용될수있을것으로생각되었다. References 1. Dolan C, Humphrey J: Governance and trade in fresh vegetables: the impact of UK supermarkets on the African horticulture industry. J. Dev. Stud. 37, 147-176 (2000). 2. Reardon T, Timmer CP, Barrett CB, Berdegué J: The rise of supermarkets in Africa, Asia, and Latin America. Am. J. Agr. Econ. 85, 1140-1146 (2003). 3. Harris L, Farber J, Beuchat L, Parish M, Suslow T, et al.: Outbreaks associated with fresh produce: incidence, growth, and survival of pathogens in fresh and fresh-cut produce. Compr. Rev. Food. Sci. F. 2, 78-141 (2003). 4. CDC (Centers for Disease Control and Prevention): Available from: http://wwwn.cdc.gov/foodborneoutbreaks/default. aspx. Accessed on Nov. 08, 2013 (2013). 5. Sagong H-G, Lee S-Y, Chang P-S, Heu S, Ryu S, et al.: Combined effect of ultrasound and organic acids to reduce Escherichia coli O157: H7, Salmonella Typhimurium, and Listeria monocytogenes on organic fresh lettuce. Int. J. Food Microbiol. 145, 287-292 (2011). 6. Zhang S, Farber J: The effects of various disinfectants against Listeria monocytogenes on fresh-cut vegetables. Food Microbiol. 13, 311-321 (1996). 7. Beuchat L, Nail B, Adler B, Clavero M: Efficacy of spray application of chlorinated water in killing pathogenic bacteria on raw apples, tomatoes, and lettuce. J. Food Protect. 61, 1305-1311 (1998). 8. Gelinas P, Goulet J: Neutralization of the activity of eight disinfectants by organic matter. J. Appl. Bacteriol. 54, 243-247 (1983). 9. Kim J, Marshall MR, Du W-X, Otwell WS, Wei C-I: Determination of chlorate and chlorite and mutagenicity of seafood treated with aqueous chlorine dioxide. J. Agr. Food Chem. 47, 3586-3591 (1999). 10. Feng H, Sun P, Chai Y, Tong G, Zhang J, et al.: The interaction of a direct-current cold atmospheric-pressure air plasma with bacteria. IEEE T. Plasma Sci. 37, 121-127 (2009). 11. Bai N, Sun P, Zhou H, Wu H, Wang R, et al.: Inactivation of Staphylococcus aureus in water by a cold, He/O 2 atmospheric pressure plasma microjet. Plasma Processes Polym. 8, 424-431 (2011). 12. Koban I, Matthes R, Hübner N-O, Welk A, Meisel P, et al.: Treatment of Candida albicans biofilms with low-temperature plasma induced by dielectric barrier discharge and atmospheric pressure plasma jet. New J. Phys. 12, 073039 (2010). 13. Escalona VH, Aguayo E, Martínez-Hernández GB, Artés F: UV-C doses to reduce pathogen and spoilage bacterial growth in vitro and in baby spinach. Postharvest Biol. Tec.

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