Combined Effect of Thermosonication and Slightly Acidic Electrolyzed Water to Reduce Foodborne Pathogens and Spoilage Microorganisms on Fresh‐cut Kale

This study evaluated the efficacy of individual treatments (thermosonication [TS+DW] and slightly acidic electrolyzed water [SAcEW]) and their combination on reducing Escherichia coli O157:H7, Listeria monocytogenes, and spoilage microorganisms (total bacterial counts [TBC], Enterobacteriaceae, Pseudomonas spp., and yeast and mold counts [YMC]) on fresh‐cut kale. For comparison, the antimicrobial efficacies of sodium chlorite (SC; 100 mg/L) and sodium hypochlorite (SH; 100 mg/L) were also evaluated. Each 10 g sample of kale leaves was inoculated to contain approximately 6 log CFU/g of E. coli O157:H7 or L. monocytogenes. Each inoculated or uninoculated samples was then dip treated with deionized water (DW; control), TS+DW, and SAcEW at various treatment conditions (temperature, physicochemical properties, and time) to assess the efficacy of each individual treatment. The efficacy of TS+DW or SAcEW was enhanced at 40 °C for 3 min, with an acoustic energy density of 400 W/L for TS+DW and available chlorine concentration of 5 mg/L for SAcEW. At 40 °C for 3 min, combined treatment of thermosonication 400 W/L and SAcEW 5 mg/L (TS+SAcEW) was more effective in reducing microorganisms compared to the individual treatments (SAcEW, SC, SH, and TS+DW) and combined treatments (TS+SC and TS+SH), which significantly (P < 0.05) reduced E. coli O157:H7, L. monocytogenes, TBC, Enterobacteriaceae, Pseudomonas spp., and YMC by 3.32, 3.11, 3.97, 3.66, 3.62, and >3.24 log CFU/g, respectively. The results suggest that the combined treatment of TS+SAcEW has the potential as a decontamination process in fresh‐cut industry.     

Efficacy of Slightly Acidic Electrolyzed Water and UV‐Ozonated Water Combination for Inactivating Escherichia Coli O157:H7 on Romaine and Iceberg Lettuce during Spray Washing Process

Spray washing is a common sanitizing method for the fresh produce industry. The purpose of this research was to investigate the antimicrobial effect of spraying slightly acidic electrolyzed water (SAEW) and a combination of ozonated water with ultraviolet (UV) in reducing Escherichia coli O157:H7 on romaine and iceberg lettuces. Both romaine and iceberg lettuces were spot inoculated with 100 μL of a 3 strain mixture of E. coli O157:H7 to achieve an inoculum of 6 log CFU/g on lettuce. A strong antimicrobial effect was observed for the UV‐ozonated water combination, which reduced the population of E. coli by 5 log CFU/g of E. coli O157:H7 on both lettuces. SAEW achieved about 5 log CFU/g reductions in the bacterial counts on romaine lettuce. However, less than 2.5 log CFU/g in the population of E. coli O157:H7 was reduced on iceberg lettuce. The difference may be due to bacteria aggregation near and within stomata for iceberg lettuce but not for romaine lettuce. The UV light treatment may stimulate the opening of the stomata for the UV‐ozonated water treatment and hence achieve better bacterial inactivation than the SAEW treatment for iceberg lettuce. Our results demonstrated that the combined treatment of SAEW and UV‐ozonated water in the spray washing process could more effectively reduce E. coli O157:H7 on lettuce, which in turn may help reduce incidences of E. coli O157:H7 outbreaks.     

应用PCR-DGGE监测酸性电解水对虾的杀菌效果

目的：考察酸性电解水对虾的杀菌效果。样品虾处理方法为：室温(20℃)条件下酸性电解水处理不同时间(处理1min或5min);不同温度(20℃或50℃)酸性电解水处理5min;室温(20℃)条件下不同处理液(酸性电解水或2%乙酸)处理5min。利用平板培养结合PCR-DGGE技术监测酸性电解水对虾的杀菌效果。结果：50℃酸性电解水处理,虾中菌数减少1.44 lg(CFU/g),其他处理减少小于1.0 lg(CFU/g);不同处理时间对杀菌效果影响不显著;2%乙酸或50℃酸性电解水的杀菌效果显著高于室温酸性电解水(P＜0.05);PCR-DGGE指纹图谱分析结果显示：50℃酸性电解水处理后,虾中细菌种类不变,其他处理比对照(无处理)有不同程度的减少;处理1min的DGGE指纹图谱和对照极相似;50℃酸性电解水处理和对照中等不相似;其他处理和对照中等相似。结论：50℃酸性电解水对虾具有较好的杀菌效果,PCR-DGGE技术能用于监测酸性电解水对虾的杀菌效果。     

Storage Stability of Slightly Acidic Electrolyzed Water and Circulating Electrolyzed Water and Their Property Changes after Application

Slightly acidic electrolyzed water (SAEW) has been recognized as an effective bactericidal agent with free chlorine, but its limitations include its instability and its great dependence on equipment. Newly developed circulating electrolyzed water (CEW) with a higher available chlorine concentration (ACC) could successfully overcome these limitations. In this study, SAEW (ACC of 20 mg/L), CEW₁ (ACC of 200 mg/L), and CEW₂ (ACC of 20 mg/L) were evaluated for changes in properties (pH, oxidization reduction potential [ORP], and ACC) during storage in open or closed glass bottles under light or dark conditions at room temperature (approximately 20 °C) and after washing pork and lettuce. Additionally, the washed pork and lettuce were evaluated for total viable counts, pH and general appearance. The results showed that CEW₁ with a higher ACC has better stability than SAEW with a lower ACC for the storage and washing experiments, and CEW still remained stable after dilution with distilled water. The property indices of EW were greatly affected for the pork‐washing experiments compared with the lettuce‐washing experiments, probably due to the existence of alkaline and organic materials on the surface of pork. Furthermore, EWs were more effective for inactivating microbes in lettuce than in pork, while there was no significant difference in tissue pH and the general appearance of pork and lettuce. These findings indicated that CEW with a higher ACC shows potential for reducing foodborne pathogens on pork and lettuce without effects on their physicochemical characteristics, and it can be applied in a diluted form.     

有机干扰物对超氧化电位水杀菌效果影响研究

试验以牛血清白蛋白(BSA)为有机干扰物质,大肠杆菌为灭菌对象,通过悬液定量杀菌试验和理化分析方法研究有机干扰物质对超氧化电位水(NEOW)杀菌效果影响。试验结果显示:在不含有机干扰物时,NEOW作用30 s,能够将菌落数对数值为7.76的大肠杆菌完全杀灭。用无菌水对NEOW稀释后,pH和氧化还原电位(ORP)变化不明显,有效氯浓度(ACC)随着稀释度的增加而降低,但稀释至60%时同样保持快速杀灭能力。在干扰物作用下,随着BSA浓度增加,NEOW杀菌效果降低。但NEOW在低浓度BSA的干扰下,可以通过增加杀菌时间或者增加有效氯浓度达到杀菌效果;在高浓度BSA的干扰下,需要对消毒环境进行预先清洗降低干扰物的量再进行消毒。     

酸性电解水冰对南美白对虾杀菌保鲜效果的研究

为探究酸性电解水冰(AEW ice)对水产品的杀菌保鲜效果,本文以夏季鲜活南美白对虾为研究对象,对其冰藏过程中感官、物理、化学及微生物菌落多样性的变化进行了研究。结果表明,在南美白对虾冰藏过程中,相较于传统自来水冰(TW ice),AEW ice对其感官评分不会产生不利影响;AEW ice能够显著降低色差值的变化(p0.05);AEW ice可以减缓冰藏过程中p H值的变化,尤其贮藏至第8 d,p H值受到明显抑制(p0.05);AEW ice在一定程度上抑制了硫代巴比妥酸(TBA)的生成。此外,PCR-DGGE结果显示AEW ice处理组DGGE图谱条带数和微生物菌落多样性指数(H′)低于TW ice处理组,表明AEW ice有效减少了微生物菌落多样性。因此,AEW ice作为一种新型高效杀菌保鲜技术,具有潜在的应用前景,可替代传统TW ice应用于水产品贮藏保鲜,以保证其食用品质并延长货架期。     

Growth Potential of Listeria Monocytogenes and Staphylococcus Aureus on Fresh‐Cut Tropical Fruits

The objective of this study was to evaluate the fate of Staphylococcus aureus, Listeria monocytogenes, and natural microbiota on fresh‐cut tropical fruits (pitaya, mango, papaya and pineapple) with commercial PVC film at different storage temperature (5, 13, and 25 °C). The results showed that S. aureus, L. monocytogenes, and natural microbiota increased significantly on fresh‐cut tropical fruits at 25 °C. Both pathogen and natural microbiota were able to grow on fresh‐cut tropical fruits at 13 °C. The maximum population of L. monocytogenes was higher than that of S. aureus on fresh‐cut tropical fruits. L. monocytogenes and S. aureus could survive without growth on fresh‐cut pitaya, mango, and papaya at 5 °C. The population of L. monocytogenes declined significantly on fresh‐cut pineapple at all temperature, indicating composition of fresh‐cut pineapple could inhibit growth of L. monocytogenes. However, S. aureus was still able to grow on fresh‐cut pineapple at storage temperature. Thus, this study suggests that 4 kinds of fresh‐cut tropical fruits (pitaya, mango, papaya, and pineapple) should be stored at low temperature to extend shelf life as well as to ensure the safety of fresh‐cut fruits.     

Fresh‐Cut Onion: A Review on Processing,Health Benefits,and Shelf‐Life

The ready‐to‐eat produce market has grown rapidly because of the health benefits and convenience associated with these products. Onion is widely used as an ingredient in an extensive range of recipes from breakfast to dinner and in nearly every ethnic cuisine. However, cutting/chopping of onion is a nuisance to many consumers due to the lachrymatory properties of the volatiles generated that bring tears to eyes and leave a distinct odor on hands. As a result, there is now an increasing demand for fresh‐cut, value‐added, and ready‐to‐eat onion in households, as well as large‐scale uses in retail, food service, and various food industries, mainly due to the end‐use convenience. Despite these benefits, fresh‐cut onion products present considerable challenges due to tissue damage, resulting in chemical and physiological reactions that limit product shelf‐life. Intensive discoloration, microbial growth, softening, and off‐odor are the typical deteriorations that need to be controlled through the application of suitable preservation methods. This article reviews the literature related to the fresh‐cut onion, focusing on its constituents, nutritional and health benefits, production methods, quality changes throughout storage, and technologies available to increase product shelf‐life.     

Impact of Mixtures of Different Fresh‐Cut Fruits on Respiration and Ethylene Production Rates

Packaging and storage of fresh‐cut fruits and vegetables are a challenging task, since fresh produce continue to respire and senesce after harvest and processing accelerates the physiological processes. The response on respiration and ethylene production rates of fresh produce to changes in O₂ and CO₂ concentrations and temperature has been extensively studied for whole fruits but literature is limited on processed and mixed fresh‐cut fruits. This study aimed to investigate the effects of mixing various proportions of fresh‐cut fruits (melon chunks, apple slices, and pineapples cubes) on respiration and ethylene production rates and to develop predictive models for modified atmosphere packaging. The experiment was designed according to a simplex lattice method and respiration and ethylene production rates were measured at 10 °C. Results showed that single component pineapple cubes, apple slices, and melon chunks, in this order, had significant constant coefficients (P = 0.05) and the greatest impact on respiration rate while the interactive binary and tertiary coefficients were insignificant. For ethylene production rates, single component apple slices, melon chunks, and pineapple cubes, and their 3‐component mixtures, in this order, had significant constant coefficients (P = 0.05) while binary coefficients were insignificant. Mathematical models were developed and validated; the cubical model was the best to describe the influence of proportion of fruit on respiration and ethylene production rates, however, considering simplicity the linear part of the model is recommended to quantify respiration and ethylene production rates of mixed fresh‐cut fruits.