Efficacy of acidic electrolyzed water ice for pathogen control on lettuce

Acidic electrolyzed water (AcEW) was used as frozen AcEW (AcEW-ice) for inactivation of Listeria monocytogenes and Escherichia coli O157:H7 on lettuce. AcEW-ice was prepared from AcEW with 20, 50, 100, and 200 ppm of available chlorine by freezing at -40 degrees C and generated 30, 70, 150, and 240 ppm of chlorine gas (Cl2), respectively. The AcEW-ice was placed into styrene-foam containers with lettuce samples at 20 degrees C for 24 h. Although AcEW-ice generating 30 ppm Cl2 had no effect on L. monocytogenes cell counts, AcEW-ice generating 70 to 240 ppm of Cl2 significantly (P < 0.05) reduced L. monocytogenes by ca. 1.5 log CFU/g. E. coli O157:H7 cell counts were reduced by 1.0 log CFU/g with AcEW-ice generating 30 ppm of Cl2. AcEW-ice generating 70 and 150 ppm of Cl2 reduced E. coli O157:H7 by 2.0 log CFU/g. Further significant reduction of E. coli O157:H7 (2.5 log CFU/g) was demonstrated by treatment with AcEW-ice generating 240 ppm of Cl2. However, treatment with AcEW-ice generating 240 ppm of Cl2 resulted in a physiological disorder resembling leaf burn. AcEW-ice that generated less than 150 ppm of Cl2 had no effect on the surface color of the lettuce. AcEW-ice, regardless of the concentration of the emission of Cl2, had no effect on the ascorbic acid content in the lettuce. The weight ratio of lettuce to AcEW-ice required was determined to be over 1:10. The bactericidal effect of AcEW-ice appeared within the first 2 h. The use of AcEW-ice provides simultaneously for low temperature storage and inactivation of bacteria.     

Decontamination of lettuce using acidic electrolyzed water

The disinfectant effect of acidic electrolyzed water (AcEW), ozonated water, and sodium hypochlorite (NaOCl) solution on lettuce was examined. AcEW (pH 2.6; oxidation reduction potential, 1140 mV; 30 ppm of available chlorine) and NaOCl solution (150 ppm of available chlorine) reduced viable aerobes in lettuce by 2 log CFU/g within 10 min. For lettuce washed in alkaline electrolyzed water (AIEW) for 1 min and then disinfected in AcEW for 1 min, viable aerobes were reduced by 2 log CFU/g. On the other hand, ozonated water containing 5 ppm of ozone reduced viable aerobes in lettuce 1.5 log CFU/g within 10 min. It was discovered that AcEW showed a higher disinfectant effect than did ozonated water significantly at P < 0.05. It was confirmed by swabbing test that AcEW, ozonated water, and NaOCI solution removed aerobic bacteria, coliform bacteria, molds, and yeasts on the surface of lettuce. Therefore, residual microorganisms after the decontamination of lettuce were either in the inside of the cellular tissue, such as the stomata, or making biofilm on the surface of lettuce. Biofilms were observed by a scanning electron microscope on the surface of the lettuce treated with AcEW. Moreover, it was shown that the spores of bacteria on the surface were not removed by any treatment in this study. However, it was also observed that the surface structure of lettuce was not damaged by any treatment in this study. Thus, the use of AcEW for decontamination of fresh lettuce was suggested to be an effective means of controlling microorganisms.     

Efficacy of neutral electrolyzed water (NEW) for reducing microbial contamination on minimally-processed vegetables

Consumption of minimally-processed, or fresh-cut, fruit and vegetables has rapidly increased in recent years, but there have also been several reported outbreaks associated with the consumption of these products. Sodium hypochlorite is currently the most widespread disinfectant used by fresh-cut industries. Neutral electrolyzed water (NEW) is a novel disinfection system that could represent an alternative to sodium hypochlorite. The aim of the study was to determine whether NEW could replace sodium hypochlorite in the fresh-cut produce industry. The effects of NEW, applied in different concentrations, at different treatment temperatures and for different times, in the reduction of the foodborne pathogens Salmonella, Listeria monocytogenes and Escherichia coli O157:H7 and against the spoilage bacterium Erwinia carotovora were tested in lettuce. Lettuce was artificially inoculated by dipping it in a suspension of the studied pathogens at 10(8), 10(7) or 10(5) cfu ml(-1), depending on the assay. The NEW treatment was always compared with washing with deionized water and with a standard hypochlorite treatment. The effect of inoculum size was also studied. Finally, the effect of NEW on the indigenous microbiota of different packaged fresh-cut products was also determined. The bactericidal activity of diluted NEW (containing approximately 50 ppm of free chlorine, pH 8.60) against E. coli O157:H7, Salmonella, L. innocua and E. carotovora on lettuce was similar to that of chlorinated water (120 ppm of free chlorine) with reductions of 1-2 log units. There were generally no significant differences when treating lettuce with NEW for 1 and 3 min. Neither inoculation dose (10(7) or 10(5) cfu ml(-1)) influenced the bacterial reduction achieved. Treating fresh-cut lettuce, carrot, endive, corn salad and 'Four seasons' salad with NEW 1:5 (containing about 50 ppm of free chlorine) was equally effective as applying chlorinated water at 120 ppm. Microbial reduction depended on the vegetable tested: NEW and sodium hypochlorite treatments were more effective on carrot and endive than on iceberg lettuce, 'Four seasons' salad and corn salad. The reductions of indigenous microbiota were smaller than those obtained with the artificially inoculated bacteria tested (0.5-1.2 log reduction). NEW seems to be a promising disinfection method as it would allow to reduce the amount of free chlorine used for the disinfection of fresh-cut produce by the food industry, as the same microbial reduction as sodium hypochlorite is obtained. This would constitute a safer, 'in situ', and easier to handle way of ensuring food safety.     

不同处理对酸性电解水物理化学特性的影响

酸性电解水是稀盐或稀酸溶液在电场作用下电解生成的水溶液,其物理化学特性对杀菌效果有很大影响.考察不同电解质溶液(NaCl、KCl、MgCl2和CaCl2)的电解特性和静置、搅拌、加热、冷却和光照处理方式对酸性电解水的pH、ORP、电导率和有效氯浓度的影响.结果表明4种盐类电解质的电解特性相似,均随着电解时间的增加,pH值降低,ORP值、电导率和有效氯含量升高,且在电解初期DH值和ORP值变化显著,然后趋于平缓.相同电解条件下,KCl溶液具有最优的电解特性.酸性电解水的pH值和ORP值在各种处理中均较为稳定,温度对电导率的影响较大.4种处理都引起有效氯浓度的明显降低,其中加热、光照和搅拌对它的影响最显著,这可能会影响到酸性电解水的杀菌效果.     

Decontaminative effect of frozen acidic electrolyzed water on lettuce

We investigated the effects of frozen acidic electrolyzed water (AcEW) on lettuce during storage in a styrene-foam container. The lettuce was kept at 2 to 3 degrees C for 24 h. Populations of aerobic bacteria associated with lettuce packed in frozen AcEW were reduced by 1.5 log CFU/g after storage for 24 h. With frozen tap water, no microorganism populations tested in this study were reduced. A frozen mixture of AcEW and alkaline electrolyzed water (AlEW) also failed to reduce populations of microorganisms associated with lettuce. Although chlorine gas was produced by frozen AcEW, it was not produced by the AcEW-AlEW mixture. This result indicates that the main factor in the decontaminative effect of frozen AcEW was the production of chlorine gas. Accordingly, low-temperature storage and decontamination could be achieved simultaneously with frozen AcEW during distribution.     

弱酸性电位水对单增李斯特菌致死机制的研究

目的研究弱酸性电位水(slightly acidic electrolyzed water,SAEW)对单增李斯特菌的致死机制,并与强碱性杀菌剂次氯酸钠(Na Cl O)和强酸性杀菌剂稀盐酸(HCl)进行比较。方法测定三种杀菌剂的杀菌效率及处理后胞内蛋白泄漏量、TTC-脱氢酶相对活性、Na+/K+-ATP酶活性和细菌超微结构的变化。结果 30 mg/L SAEW和Na Cl O对Na+/K+-ATP酶和TTC-脱氢酶相对活性的抑制无显著性差异,但其显著高于稀HCl组。SAEW处理单增李斯特菌1 min后所导致的蛋白质泄漏量(0.35 mg/m L)显著高于Na Cl O和稀HCl处理组(分别为0.16mg/m L和0.11 mg/m L)。SAEW、Na Cl O、稀HCl对单增李斯特菌的细胞超微结构都造成了明显的损伤,细胞质凝集,透电子区扩大。其中稀HCl对超微结构的损伤最大,说明强酸性环境对细胞形态结构有很大的影响。结论 SAEW处理对单增李斯特菌细胞质造成了一定程度的损伤,抑制了细胞呼吸作用,改变了细胞膜的通透性,降低了细胞膜上的Na+/K+-ATP酶活性,导致细胞内大分子物质泄漏而最终导致细胞死亡。SAEW杀菌机制的初步研究为未来SAEW的杀菌研究和应用前景奠定基础。     

芽菜生产中利用电生功能水控制微生物污染的研究

芽菜中的微生物主要由生产芽菜所用种子带入,人们误食被病原菌污染的芽菜后会出现食物中毒现象。研究采用电生功能水对黄豆、绿豆、苜蓿和萝卜4种芽菜种子进行浸泡前处理,达到杀灭种子表面的微生物的目的。实验结果显示:电生功能水可以有效降低种子表面的微生物数量,处理后黄豆和绿豆种子表面的微生物总数均小于1logcfu/g,苜蓿和萝卜种子表面的微生物总数分别为(3.53±0.07)logcfu/g和(2.65±0.14)logcfu/g。对绿豆种子表面的电镜扫描结果显示:碱性水和微酸性水相结合的方式可以严重破坏绿豆种子表层的蜡质层,增强杀菌效果。结果还发现,电生功能水处理使黄豆种子的发芽率由85%提高到89%,萝卜种子的发芽率由62%提高到80%,对绿豆和苜蓿种子的发芽率没有显著影响。     

Reduction of Salmonella enterica on alfalfa seeds with acidic electrolyzed oxidizing water and enhanced uptake of acidic electrolyzed oxidizing water into seeds by gas exchange

Alfalfa sprouts have been implicated in several salmonellosis outbreaks in recent years. The disinfectant effects of acidic electrolyzed oxidizing (EO) water against Salmonella enterica both in an aqueous system and on artificially contaminated alfalfa seeds were determined. The optimum ratio of seeds to EO water was determined in order to maximize the antimicrobial effect of EO water. Seeds were combined with EO water at ratios (wt/vol) of 1:4, 1:10, 1:20, 1:40, and 1:100, and the characteristics of EO water (pH, oxidation reduction potential [ORP], and free chlorine concentration) were determined. When the ratio of seeds to EO water was increased from 1:4 to 1:100, the pH decreased from 3.82 to 2.63, while the ORP increased from +455 to +1,073 mV. EO water (with a pH of 2.54 to 2.38 and an ORP of +1,083 to +1,092 mV) exhibited strong potential for the inactivation of S. enterica in an aqueous system (producing a reduction of at least 6.6 log CFU/ml). Treatment of artificially contaminated alfalfa seeds with EO water at a seed-to-EO water ratio of 1:100 for 15 and 60 min significantly reduced Salmonella populations by 2.04 and 1.96 log CFU/g, respectively (P < 0.05), while a Butterfield's buffer wash decreased Salmonella populations by 0.18 and 0.23 log CFU/g, respectively. After treatment, EO water was Salmonella negative by enrichment with or without neutralization. Germination of seeds was not significantly affected (P > 0.05) by treatment for up to 60 min in electrolyzed water. The uptake of liquid into the seeds was influenced by the internal gas composition (air, N2, or O2) of seeds before the liquid was added.     

微酸性电解水在食品保鲜消毒领域的应用

微酸性电解水(slightly acidic electrolyzed water, SAEW)是一种具有巨大潜力的非热杀菌技术,目前主要在无隔膜装置中利用直流电流电解进行制备。SAEW的pH值为5.0～6.5,主要成分为强氧化性的次氯酸,能够通过破坏微生物细胞结构和影响微生物生理生化反应来杀灭致病菌。SAEW不但可以高效杀菌,还能同时保持食品的物理品质、营养品质和感官特性。相比较传统的杀菌技术,SAEW具有杀菌广谱、安全无毒、制取成本低、储存稳定性较好等优势,因此越来越受到人们的关注并被广泛研究应用。本文综述了微酸性电解水的制取原理、杀菌机制与特点及微酸性电解水对食品品质的影响与应用现状,并指出了当前研究的局限性和未来研究方向。旨在为微酸性电解水的理论研究和应用提供参考,以期其能在食品行业得到更好的开发推广,提高食品的质量安全。     

酸性电解水对鸡白痢沙门氏菌杀灭效果的研究

家禽和禽产品中的沙门氏菌是引起人类沙门氏菌感染和食物中毒的主要潜在来源,沙门氏菌通常被认为是生产者和消费者所面临的最严重的致病菌之一.研究不同电解质种类和电解时间等参数条件下制得的酸性电解水对鸡白痢沙门氏菌的杀灭效果,确定了酸性电解水 pH 值和有效氯浓度对杀菌效果的影响.结果表明,酸性电解水对鸡白痢沙门氏菌具有较强的杀灭效果,当酸性电解水pH值小于3或有效氯浓度超过1 mg/kg 时可以100%杀灭鸡白痢沙门氏菌,且 NaCl、KCl 溶液制得的酸性电解水的杀菌效果优于 CaCl2、MgCl2溶液制得的酸性电解水.     

酸性电解水对蔬菜杀菌效果的研究

通过使用酸性电解水对豆芽进行杀菌处理,探讨了酸性电解水的用量、pH、杀菌时间、处理次数等因素对豆芽杀菌效果的影响。试验结果表明,酸性电解水的使用量不影响杀菌效果;酸性电解水的pH越小,杀菌效果越显著;处理时间越长,杀菌效果越好;多次处理的杀菌效果好于1次处理的。     

酸性电解水用于葡萄杀菌保鲜的试验研究

用不同指标的酸性电解水对葡萄进行处理,对处理后果实的微生物总数、霉菌总数以及腐烂率、脱粒率进行了对比研究,结果显示:经不同指标酸性电解水浸泡处理后,果实表面微生物数量均显著降低,果实的总损失率也明显降低;对比发现,强酸性电解水的防腐保鲜效果最优;葡萄果实采后用酸性电解水处理可以有效的提高其商品价值及食用安全性。     

Prediction of microbial growth in fresh-cut vegetables treated with acidic electrolyzed water during storage under various temperature conditions.

Effects of storage temperature (1, 5, and 10 degrees C) on growth of microbial populations (total aerobic bacteria, coliform bacteria, Bacillus cereus, and psychrotrophic bacteria) on acidic electrolyzed water (AcEW)-treated fresh-cut lettuce and cabbage were determined. A modified Gompertz function was used to describe the kinetics of microbial growth. Growth data were analyzed using regression analysis to generate "best-fit" modified Gompertz equations, which were subsequently used to calculate lag time, exponential growth rate, and generation time. The data indicated that the growth kinetics of each bacterium were dependent on storage temperature, except at 1 degrees C storage. At 1 degrees C storage, no increases were observed in bacterial populations. Treatment of vegetables with AcEW produced a decrease in initial microbial populations. However, subsequent growth rates were higher than on nontreated vegetables. The recovery time required by the reduced microbial population to reach the initial (treated with tap water [TW]) population was also determined in this study, with the recovery time of the microbial population at 10 degrees C being <3 days. The benefits of reducing the initial microbial populations on fresh-cut vegetables were greatly affected by storage temperature. Results from this study could be used to predict microbial quality of fresh-cut lettuce and cabbage throughout their distribution.     

微酸性电解水对黄瓜的消毒效果及安全性评价

目的评价微酸性电解水对黄瓜的消毒效果及安全性能。方法以黄瓜为载体,以大肠杆菌及黄瓜表面的自然菌为指标菌,探究微酸性电解水的消毒效果,并通过一次性皮肤刺激试验及急性经口毒性试验,评价其安全性能。结果 1%大豆卵磷脂、1%硫代硫酸钠、3%吐温80的复配使用能有效中和有效氯浓度为50 mg/L、pH值为6.5的微酸性电解水;微酸性电解水对黄瓜表面的自然菌及添加的大肠杆菌的杀菌效果显著,30次消毒试验后的平均杀灭对数值分别达到2.18和3.08;微酸性电解水小鼠急性经口毒性评价属实际无毒级别,家兔皮肤刺激强度属无刺激。结论微酸性电解水对黄瓜表面的消毒效果显著,且安全、绿色、环保,是一种比较理想的食品消毒剂。     

酸性电解水对副溶血性弧菌和单核细胞增生李斯特氏菌杀菌效果的比较研究

目的研究不同浓度酸性电解水对副溶血性弧菌和单核细胞增生李斯特氏菌单增李斯特菌的杀菌作用,比较酸性电解水对革兰氏阴性菌和革兰氏阳性菌的杀菌效果。方法采用传统的平板计数法进行细菌计数,扫描电镜观察细菌细胞的形态变化,琼脂糖胶电泳检测细菌DNA变化和BSA法进行细菌蛋白质泄露测定。结果酸性电解水对副溶血性弧菌和单核细胞增生李斯特氏菌均具有很强的杀灭效果,其杀菌效果随着电解水浓度的增加而增强。较高浓度的电解水处理后,副溶血性弧菌几乎全部杀灭,单核细胞增生李斯特氏菌菌落总数降低了1.45 log CFU/mL。扫描电镜实验表明,经酸性电解水处理的副溶血性弧菌坍塌明显,且随着酸性电解水浓度的升高,细胞形态崩解严重,细菌形状模糊。结论相较于单核细胞增生李斯特氏菌,酸性电解水对革兰氏阴性菌副溶血性弧菌有明显的杀菌效果     

基于酸性电解水处理的金枪鱼杀菌技术研究

以金枪鱼（鲣鱼,Skipjack tuna）为研究对象,重点评价酸性电解水镀冰衣对于冷冻鱼肉的抑菌效果,以及不同杀菌剂对于金枪鱼生鱼片的杀菌效果。结果表明:a.-18℃冻藏条件下,pH4.5酸性电解水镀冰衣可显著降低金枪鱼肉中的细菌总数和大肠埃希氏菌数量;b.杀菌剂食醋、芥末及酸性电解水对金枪鱼生鱼片的杀菌效果显著（p<0.05）,煮沸后的酱油基本无杀菌效果;c.金枪鱼生鱼片最佳杀菌剂配方:食醋8.0mL、0.1g芥末（酱）、1.0mL酸性电解水及少量加饭酒。研究结果为冷冻金枪鱼新型镀冰衣技术的研发奠定理论基础,也为消费者安全食用生食金枪鱼生鱼片提供科学指导。      

微酸性电解水对罗非鱼片保鲜效果的研究

为探讨微酸性电解水在罗非鱼加工应用的前景,开展微酸性电解水对罗非鱼片的保鲜效果研究。将罗非鱼片浸泡在有效氯浓度为(31. 39±1. 48) mg/L的微酸性电解水10 min后沥干装入聚乙烯保鲜袋,置于4℃下贮藏,以感官评定、挥发性盐基氮(total volatile base nitrogen,TVB-N)值、k值、菌落总数与p H等作为评价指标,测定罗非鱼片冷藏过程中的品质变化。结果表明,在贮藏期间,对照组样品TVB-N值2～3 d超过20 mg/100 g,而实验组样品第6天刚超过20 mg/100 g,对照组样品k值2～3 d超过60%,而实验组样品5～6 d超过60%,对照组样品菌落总数2～3 d超过6 lg CFU/g,而实验组样品第6天刚超6 lg CFU/g,实验组样品p H增加始终较对照组样品慢,而实验组样品感官评分始终高于对照组样品。采用微酸性电解水处理后的罗非鱼片,对比对照组货架期延长2～3 d。为微酸性电解水在水产品保鲜技术上应用提供技术参考和依据。