电生功能水抑制微生物及其产生毒素研究进展

由于电生功能水具有广谱杀菌性、效率高、经济、安全、环保等诸多优点,近几年,在抑制或杀灭微生物活性方面受到了人们的普遍关注。目前,强酸性电生功能水的应用已较广泛,也有一些微酸性及中性电生功能水应用于农业、食品领域的报道。随着研究的不断深入,电生功能水与其他多种处理手段的结合,电生功能水杀菌成分与机理,电生功能水的杀菌条件等问题也被不断探究。本文论述电生功能水杀菌、灭活病毒、毒素等方面的最新研究进展,指出目前研究中存在的问题以及今后的发展方向。     

The antifungal mechanism of electrolyzed oxidizing water against Aspergillus flavus

Fungicidal electrolyzed oxidizing waters (EOW) include neutralized electrolyzed oxidizing water (NEW) and acidic electrolyzed oxidizing water (AcEW). These forms were evaluated against Aspergillus flavus conidia (spores) and mycelia. EOW possessed strong antifungal activities against A. flavus conidia and mycelia due to destruction of the cellular structures of the A. flavus conidium and mycelium. K⁺ and Mg²⁺ leakage results from damage to the normal cellular functions of A. flavus conidia and mycelia. Among the physicochemical parameters of EOW, the available chlorine concentration (ACC) is primarily responsible for the EOW antifungal activity. A. flavus can be eliminated by use of AcEW and NEW as a new, alternative method of fungal control that is superior to some current physical methods and to synthetic chemical fungicides.     

Roles of hydroxyl radicals in electrolyzed oxidizing water (EOW) for the inactivation of Escherichia coli

The food industry has recognized electrolyzed oxidizing water (EOW) as a promising alternative decontamination technique. However, there is not a consensus about the sanitizing mechanism of EOW. In this study, we evaluated the disinfection efficacy of different types of EOW on Escherichia coli. Based on the hypothesis of hydroxyl radicals existing in EOW, in the present study, the hydroxyl radicals existed in slightly acidic electrolyzed water (SAEW) and acidic electrolyzed water (AEW) diluted to different levels were detected quantitatively. An ultraviolet (UV) spectrophotometer was used to scan EOW with different pH values. Accounting for the results of UV scanning to EOW with different pH value and the disinfection efficacy of different types of EOW, it can be concluded that considering the lower chlorine concentration of EOW compared with traditional chlorine disinfectants, the existing form of chlorine compounds rather than the hydroxyl radicals played important role in the disinfection efficacy of EOW.     

弱酸性电位水在茭白防腐保鲜中的应用

研究弱酸性电位水（slightly acidic electrolyzed water,SAEW）处理对茭白微生物状态和贮藏品质的影响。以未经处理的茭白作对照,用有效氯质量浓度30 mg/L SAEW浸泡茭白5 min后自然晾干,包装后置于4 ℃冰箱中贮藏12 d,贮藏期内每3 d进行感官评定,测定茭白根部微生物数量及色泽、硬度、质量损失率、呼吸速率及木质素含量、蛋白质含量、VC含量、可溶性固形物含量、过氧化物酶（POD）活性、多酚氧化酶（PPO）活性和过氧化氢酶（CAT）活性。结果显示,SAEW处理后茭白根部菌落总数下降1.62（lg（CFU/g））,并且在贮藏期内能有效控制微生物数量。同时能够降低茭白贮藏期的呼吸作用,减缓茭白褐变、变软、失水、木质化,对保持可溶性固形物、VC含量有一定作用;另外SAEW处理可使POD与PPO保持在较低活性,而使CAT活性提高。结果表明,SAEW在茭白杀菌防腐、保持其贮藏品质方面具有一定的潜力。     

微酸性电解水对苦荞芽活性成分及抗氧化能力的影响

以苦荞为原料,将不同有效氯浓度（available chlorine concentration,ACC）的微酸性电解水（slightly acidic electrolyzed water,SAEW）应用于芽苗菜生产,研究其对苦荞芽活性成分及其抗氧化能力的影响。结果表明：SAEW处理组苦荞芽活性成分含量相比对照组有所增加,ACC为20 mg/L的SAEW处理的苦荞芽总酚、总黄酮及芦丁含量相比自来水对照组分别提升了28.69%、26.19%和29.08%。SAEW处理萌发的苦荞芽在生长7 d内苯丙氨酸解氨酶比活力均高于自来水对照组。苦荞芽的抗氧化活性物质含量与其抗氧化能力间呈显著正相关。     

Evaluating the effects of plasma-activated slightly acidic electrolyzed water on bacterial inactivation and quality attributes of Atlantic salmon fillets

In this study, an intervention non-thermal processing technology plasma-activated slightly acidic electrolyzed water (PASW) was developed to better preserve salmon fillets. Compared to the plasma-activated water (PAW) and slightly acidic electrolyzed water (SAEW), PASW treatment was found to be more effective in inactivating microorganisms. After PAW, SAEW, or PASW treatment for 120 s, the population of Shewanella putrefaciens (S. putrefaciens) was reduced by 2.04, 2.62 and 2.08 Log CFU/mL (P < 0.05) using plate counts, respectively. The test for the leakage of nucleic acids and protein in intracellular contents confirmed that PASW caused serious damage to the microbial cell structural integrity compared to that alone PAW or SAEW. Meanwhile, scanning electron microscopic observations also showed that PASW caused apparent bacterial structural changes. Besides, the PASW treatment did not alter color and textural properties of salmon fillets, and restrained lipid oxidation as compared to the control and SAEW treatments. In all, this study compared the bacterial inactivation mechanisms for PAW, SAEW, and PASW, and suggested that PASW was effective in inactivating S. putrefaciens of salmon fillets.Industrial relevancePlasma-activated slightly acidic electrolyzed water, an emerging technology in food processing, can be a potential green technology for the processing of aquatic food products. PASW treatment had higher disinfection efficacy than that of SAEW or PAW treatment alone, and no adverse effect on the quality of Atlantic salmon fillets. These results boost knowledge in the food preservation field, as well as the application of non-thermal processing in the food industry.     

Efficacy of Neutral Electrolyzed Water,Quaternary Ammonium and Lactic Acid‐Based Solutions in Controlling Microbial Contamination of Food Cutting Boards Using a Manual Spraying Technique

Bactericidal activity of neutral electrolyzed water (NEW), quaternary ammonium (QUAT), and lactic acid‐based solutions was investigated using a manual spraying technique against Salmonella Typhimurium, Escherichia coli O157:H7, Campylobacter jejuni, Listeria monocytogenes and Staphylococcus aureus that were inoculated onto the surface of scarred polypropylene and wooden food cutting boards. Antimicrobial activity was also examined when using cutting boards in preparation of raw chopped beef, chicken tenders or salmon fillets. Viable counts of survivors were determined as log₁₀ CFU/100 cm² within 0 (untreated control), 1, 3, and 5 min of treatment at ambient temperature. Within the first minute of treatment, NEW and QUAT solutions caused more than 3 log₁₀ bacterial reductions on polypropylene surfaces whereas less than 3 log₁₀ reductions were achieved on wooden surfaces. After 5 min of treatment, more than 5 log₁₀ reductions were achieved for all bacterial strains inoculated onto polypropylene surfaces. Using NEW and QUAT solutions within 5 min reduced Gram‐negative bacteria by 4.58 to 4.85 log₁₀ compared to more than 5 log₁₀ reductions in Gram‐positive bacteria inoculated onto wooden surfaces. Lactic acid treatment was significantly less effective (P < 0.05) compared to NEW and QUAT treatments. A decline in antimicrobial effectiveness was observed (0.5 to <2 log₁₀ reductions were achieved within the first minute) when both cutting board types were used to prepare raw chopped beef, chicken tenders or salmon fillets.     

In vitro inactivation of Escherichia coli, Staphylococcus aureus and Salmonella spp. using slightly acidic electrolyzed water

In the current study, the effectiveness of slightly acidic electrolyzed water (SAEW) on an in vitro inactivation of Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Salmonella spp. was evaluated and compared with other sanitizers. SAEW (pH 5.6, 23 mg/l available chlorine concentration; ACC; and 940 mV oxidation reduction potential; ORP) was generated by electrolysis of dilute solution of HCl (2%) in a chamber of a non-membrane electrolytic cell. One milliliter of bacteria suspension (ca. 10–11 log₁₀CFU/ml) was mixed with 9 ml of SAEW, strong acidic electrolyzed water (StAEW; ca. 50 mg/l ACC), sodium hypochlorite solution (NaOCl; ca.120 mg/l ACC) and distilled water (DW) as control and treated for 60 s. SAEW effectively reduced the population of E. coli, S. aureus and Salmonella spp. by 5.1, 4.8, and 5.2 log₁₀CFU/ml. Although, ACC of SAEW was more than 5 times lower than that of NaOCl solution, they showed no significant bactericidal difference (p > 0.05). However, the bactericidal effect of StAEW was significantly higher (p < 0.05) than SAEW and NaOCl solution in all cases. When tested with each individual test solution, E. coli, S. aureus and Salmonella spp. reductions were not significantly different (p > 0.05). These findings indicate that SAEW with low available chlorine concentration can equally inactivate E. coli, S. aureus and Salmonella spp. as NaOCl solution and therefore SAEW shows a high potential of application in agriculture and food industry as an environmentally friendly disinfection agent.     

酸性电解水对苹果表面毒死蜱降解效果及降解途径分析

目的:通过研究不同条件下的酸性电解水对苹果表面毒死蜱的降解效果以及分析毒死蜱的降解途径,为苹果生产加工行业提供理论支持。方法:使用毒死蜱模拟污染苹果表面,在不同有效氯浓度（10、50、100 mg/L）和pH（pH为2.80和5.80）的酸性电解水条件下,采取浸泡处理或振荡清洗苹果的清洗方法,用气相色谱和气质联用方法测定毒死蜱残留和降解产物。结果:通过强酸性电解水降解苹果表面的毒死蜱实验,发现其降解效率与反应时间、有效氯浓度有直接关系,随着反应时间的延长或有效氯浓度的增加,降解效率也增加。当有效氯浓度达到50 mg/L时,浸泡15 min会降解55%以上的毒死蜱残留,并且与对照组自来水浸泡有极显著差异（P<0.01）。当有效氯浓度为100 mg/L时对毒死蜱的降解率超过了70%。在相同条件下强酸性电解水与微酸性电解水在降解毒死蜱的效果上无显著差异（P>0.05）,并且浸泡处理和振荡处理对实验结果没有显著影响（P>0.05）。酸性电解水处理对苹果主要品质指标没有显著影响（P>0.05）。经GC-MS分析,毒死蜱被强酸性电解水降解后,在降解产物中发现毒死蜱氧化物（CPO）和3, 5, 6-三氯吡啶-2-醇（TCP）。其可能的降解途径为毒死蜱→CPO→TCP→小分子有机物→无机物。结论:该研究结果对苹果加工产业在消除农药残留方面提供一种新方法。     

Time Course of PPO-Related Browning of Yams

The time course of polyphenol oxidase (PPO) activity and tissue browning was investigated in five Dioscorea species. In three of the yam species, 86% of the browning was associated with the peak of PPO activity. In D dumentorum and D rotundata, only 9 and 40%, respectively, of browning was PPO-related, while most of the tissue browning occurred after PPO activity had declined to the control value. The browning incidence was temperature-dependent such that the optimal temperature for PPO activity (30°C) also coincided with that of maximal browning in all the yam species expect in D dumentorum. Classical inhibitors of PPO prevented the browning in tissues where the enzymic mechanism predominated while failing to reduce browning in D dumentorum and D rotundata where most of tissue browning was not enzyme associated. The results put the incidence of yam discolouration in proper perspective in terms of the timescale of PPO and non-PPO-catalysed discolouration.     

PARTIAL PURIFICATION AND CHARACTERIZATION OF POLYPHENOL OXIDASE FROM FRESH-CUT CHINESE WATER CHESTNUT

The characteristics of polyphenol oxidase (PPO) from Chinese water chestnut (CWC) and its potential inhibitors for browning reactions were investigated. PPO was isolated from fresh‐cut CWC and was purified on a Sephadex G‐100 column, with a yield of total activity close to 10%. The molecular weight, Michaelis constant (K_m), substrate specificity, optimal pH and temperature of CWC PPO were examined. Kinetic studies indicated that the K_m and V_max values of CWC PPO for catechol were 10.32 mmol/L and 6.452 × 10⁴ U/min, respectively. The optimal pH and temperature for CWC PPO was 6.5 and 40C, respectively. Among the browning inhibitors tested, 4‐hexylresorcinol, at a concentration of 0.3 mmol/L, showed the strongest inhibition (70%) against the PPO activity of CWC, followed by 3.0 mmol/L N‐acetyl‐L‐cysteine with an inhibition of 53%.     

Efficacy of Sanitized Ice in Reducing Bacterial Load on Fish Fillet and in the Water Collected from the Melted Ice

ABSTRACT: This study investigated the efficacy of sanitized ice for the reduction of bacteria in the water collected from the ice that melted during storage of whole and filleted Tilapia fish. Also, bacterial reductions on the fish fillets were investigated. The sanitized ice was prepared by freezing solutions of PRO-SAN^® (an organic acid formulation) and neutral electrolyzed water (NEW). For the whole fish study, the survival of the natural microflora was determined from the water of the melted ice prepared with PRO-SAN^® and tap water. These water samples were collected during an 8 h storage period. For the fish fillet study, samples were inoculated with Escherichia coli K12, Listeria innocua, and Pseudomonas putida then stored on crushed sanitized ice. The efficacies of these were tested by enumerating each bacterial species on the fish fillet and in the water samples at 12 and 24 h intervals for 72 h, respectively. Results showed that each bacterial population was reduced during the test. However, a bacterial reduction of < 1 log CFU was obtained for the fillet samples. A maximum of approximately 2 log CFU and > 3 log CFU reductions were obtained in the waters sampled after the storage of whole fish and the fillets, respectively. These reductions were significantly (P < 0.05) higher in the water from sanitized ice when compared with the water from the unsanitized melted ice. These results showed that the organic acid formulation and NEW considerably reduced the bacterial numbers in the melted ice and thus reduced the potential for cross-contamination.     

Polyphenoloxidase Activity and Color of Blanched and High Hydrostatic Pressure Treated Banana Puree

The effects of blanching and high hydrostatic pressure (HHP) treatments on natural flora evolution, polyphenoloxidase (PPO) activity and color of banana puree adjusted to pH 3.4 and water activity (a_w) of 0.97 were evaluated during 15 days storage at 25°C. Standard plate as well as yeast and mold counts of HHP treated purees were <10 CFU/g throughout storage. Blanching time was found to affect (P<0.05) puree color. HHP treatments retained the initial color of the banana purees. Longer browning induction times and slower browning rates were observed when a longer blanching time was combined with a 689 MPa pressure treatment. A residual PPO activity < 5% was observed in the puree when a 7 min blanch was followed by HHP treatment at 689 MPa for 10 min.     

Disinfection effect and its mechanism of electrolyzed oxidizing water on spores of <Emphasis Type="Italic">Bacillus subtilis</Emphasis> var. <Emphasis Type="Italic">niger</Emphasis>

A study was carried out on the disinfection efficiency of electrolyzed oxidizing water (EOW) on spores of Bacillus subtilis var. niger. The results showed a remarkable fungicidal rate of 100% after 20 min duration of 191 mg/L active available chlorine (ACC). The disinfection effect was improved with increased ACC or prolonged disinfection time, while organic interferents exerted a strong concentration-dependent inhibition against the disinfection. The disinfection mechanism was also investigated at bio-molecular level. EOW decreased dehydrogenase activity, intensified membrane permeability, elevated suspension conductivity, and caused leakage of intracellular K⁺, proteins, and DNA, indicating a damage of cell walls and membranes. Effects of EOW on microbiological ultra-structures were also verified by transmission electronic microscopy (TEM) images, showing that EOW destroyed protective barriers of the microbe and imposed some damages upon the nucleus area.     

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.     

Effects of Electrolyzed Oxidizing Water on Inactivation of Bacillus subtilis and Bacillus cereus Spores in Suspension and on Carriers

Spores of some Bacillus species are responsible for food spoilage and foodborne disease. These spores are highly resistant to various interventions and cooking processes. In this study, the sporicidal efficacy of acidic electrolyzed oxidizing (EO) water (AEW) and slightly acidic EO water (SAEW) with available chlorine concentration (ACC) of 40, 60, 80, 100, and 120 mg/L and treatment time for 1, 2, 3, 4, 5, and 6 min were tested on Bacillus subtilis and Bacillus cereus spores in suspension and on carrier with or without organics. The reduction of spore significantly increased with increasing ACC and treatment time (P < 0.05). Nondetectable level of B. cereus spore in suspension occurred within 2 min after exposure to both EO waters containing 120 mg/L ACC, while only SAEW at 120 mg/L and 2 min treatment achieved >6 log reductions of B. subtilis spore. Both types of EO water with ACC of 60 mg/L and 6 min treatment achieved a reduction of B. subtilis and B. cereus spores to nondetectable level. EO water with ACC of 80 mg/L and treatment time of 3 min on carrier test without organics addition resulted in reductions of B. subtilis spore to nondetectable level. But, addition of 0.3% organics on carrier decreased the inactivation effect of EO water. This study indicated that EO water was highly effective in inactivation of B. subtilis and B. cereus spores in suspension or on carrier, and therefore, rendered it as a promising disinfectant to be applied in food industry.     

Effect of rice bran protein extract on enzymatic browning inhibition in potato puree

Effect of rice bran protein extract (RBPE) on enzymatic browning inhibition in potato puree was studied by colour measurement and polyphenol oxidase (PPO) inhibition. RBPE inhibited browning in potato puree and showed a higher per cent potato PPO inhibition at pH 4.0 and 5.0 than those at pH 3.0, 6.0 and 7.0 (P ≤ 0.05). RBPE heated to 40 and 60 °C had browning inhibition in potato puree and per cent potato PPO inhibition at a similar extent to unheated RBPE (P > 0.05). Browning inhibition and per cent potato PPO inhibition of RBPE were decreased when it was heated to 80 °C (P ≤ 0.05). RBPE inhibited browning in potato puree higher than 5, 10 and 20 mm ascorbic acid and 5 and 10 mm citric acid (P ≤ 0.05). Regarding the kinetics study, RBPE exhibited a mixed‐type inhibition for potato PPO. Therefore, RBPE has a potential to be used as a natural antibrowning agent in the potato industry.     

Differences of Bactericidal Efficacy on <Emphasis Type="Italic">Escherichia coli</Emphasis>, <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>, and <Emphasis Type="Italic">Bacillus subtilis</Emphasis> of Slightly and Strongly Acidic Electrolyzed Water

In the present study, the disinfection efficacy of slightly acidic electrolyzed water (SAEW) and strongly acidic electrolyzed water (AEW) was tested on three bacteria, Escherichia coli, Staphylococcus aureus, and Bacillus subtilis and the disinfection mechanism was discussed. The results showed that SAEW had a stronger antibacterial efficacy against these tested bacteria in comparison with AEW. The results also showed that both SAEW and AEW treatments could damage the cell membrane, which was demonstrated microcosmically by scanning electron microscopy (SEM), thus causing leakages of protein, DNA, RNA, and ATP, resulting in the death of microbes. Moreover, AEW treatment could not cause the degradations of DNA and RNA, and nucleic acids including DNA and RNA are not the target point of its bactericidal efficacy. However, SAEW could maybe cause the degradation of RNA, and RNA may be the target in its antibacterial activity. We suggested that the differences in antibacterial efficacy between SAEW and AEW could be explained by the different impacts on RNA of tested strains.     

Effect of high oxygen modified atmosphere on post‐harvest physiology and sensorial qualities of mushroom

The changes in physiology and sensorial qualities of mushroom stored at 2 °C for 12 days under high oxygen (100% O₂, 80% O₂) atmosphere and air had been investigated. Respiration rate was suppressed in mushroom in 80% O₂ and 100% O₂. No significant differences were found between 80% O₂ and 100% O₂. Weight loss was not more than 1.5% in all treatments. Weight loss and firmness of mushroom held in high oxygen were significantly (P < 0.05) higher than in air. Total soluble solid (TSS) was only slightly affected by high oxygen treatment. High oxygen, especially 100% O₂ treatment was effective at reducing browning degree and electrolyte leakage of mushroom. The surface colour of mushroom changed slightly before tenth day under high oxygen treatment. From day 2 the L‐value of mushroom flesh was significantly (P < 0.05) lower under air atmosphere compared with high oxygen treated mushroom. High oxygen, especially 100% O₂ was effective at inhibiting discoloration. The PPO activity of mushroom was significantly (P < 0.05) higher in 100% O₂ compared with air treatment. The POD activity was highest in high oxygen at eighth day, then reduced. High oxygen, especially 100% O₂ was effective at maintaining the quality of mushroom.     

IDENTIFICATION OF PROCYANIDIN A2 AS POLYPHENOL OXIDASE SUBSTRATE IN PERICARP TISSUES OF LITCHI FRUIT

Postharvest browning of litchi fruit results in short shelf life and reduced commercial value. Experiments were conducted to separate, purify and identify polyphenol oxidase (PPO ) substrates that cause litchi fruit to brown. PPO and its substrate were extracted from the pericarp tissues of litchi fruit. The litchi PPO substrate was purified using polyamide column, silica gel column and Sephadex LH‐20 column chromatography. The browning substrate was selected by a 0.5% FeCl₃ solution and then identified using a partially purified litchi PPO. Analyses of ultraviolet spectrometry, nuclear magnetic resonance and electrospray ionization mass spectrometry indicated that the PPO substrate was procyanidin A2. The substrate can be oxidized to ο‐quinones by litchi PPO and then form brown‐colored by‐products, resulting in pericarp browning of harvested litchi fruit.