Control of Salmonella in food related environments by chemical disinfection

Salmonella may be transferred to food through cross-contamination during processing and preparation. To minimise the risk of cross-contamination, proper cleaning and disinfection is essential for the food industry. Recently, disinfection of areas for preparation and storage of food has also gained increased popularity in households. There is a range of disinfectants available with different properties and usage areas, and care must be taken to choose the proper disinfectant for the specific application.There are many methods for testing the antimicrobial effect of disinfectants. To evaluate whether a disinfectant will be effective in practical settings, the test method should model real-life situations. Most disinfectants are effective against Salmonella at recommended user concentration in suspension tests. However, a number of factors may reduce the biocidal effect of disinfectants under practical conditions. This include properties of the surface to be disinfected, presence of soiling on the surface, the physiological state of the bacteria exposed to disinfection, including bacteria embedded in biofilms, and the effects of other stresses (e.g. desiccation, starvation and temperature).Here we review the effects of disinfectants used in food related areas in industries and in households against Salmonella. A general overview is given for disinfectants in use and methods used to evaluate effects. Effects of disinfectants against Salmonella in suspension and on surfaces, including biofilms, are presented and compared. Novel control strategies such as use of electrolysed water, antimicrobial surfaces, and anti-biofilm compounds are also covered. Finally, we review the ability of Salmonella to gain reduced susceptibility to disinfectants through adaptation and other physiological responses like biofilm formation.     

Aeromonas biofilm on stainless steel: efficiency of commonly used disinfectants

Aeromonas spp. are ubiquitous bacteria widely distributed among aquatic environments that have the ability to form biofilms. This aptitude allows them to persist in water distribution systems, contaminating drinking water, food processing surfaces and ultimately food. For this study, the biofilm‐forming ability of aeromonads was evaluated after 48‐h incubation on stainless steel discs at both 4 and 20 °C. Subsequently, disinfectants based on amphoteric surfactants and chlorine compounds were evaluated regarding the capacity to eradicate preformed biofilm and inhibit biofilm formation. Results obtained demonstrated that all strains under analysis were able to form biofilm at both room and refrigeration temperatures. The chlorine‐based disinfectant demonstrated to be efficient in removing preformed biofilm, but both were unsuccessful in preventing biofilm formation, highlighting the importance of adequate cleaning and disinfection procedures, with emphasis on food processing surfaces.     

Alternative disinfection methods to chlorine for use in the fresh-cut industry

The use of chlorine as a disinfectant in the fresh-cut produce industry has been identified as a concern mainly due to public health issues. In fact, this chemical, commonly used as hypochlorous acid and hypochlorite, has already been prohibited in some European countries, due to the potential production of toxic by-products, such as chloroform and other trihalomethanes, chloramines and haloacetic acids. The search for alternative methods of disinfection is therefore a current and on-going challenge in both Academia and Industry. Some methods are well described in the literature on the disinfection of food-contact surfaces and process water and also on the decontamination of the produce. These methods are commonly classified as biological (bacteriocins, bacteriophages, enzymes and phytochemicals), chemical (chlorine dioxide, electrolyzed oxidizing water, hydrogen peroxide, ozone, organic acids, etc) and physical (irradiation, filtration, ultrasounds, ultraviolet light, etc). This review provides updated information on the state of art of the available disinfection strategies alternative to chlorine that can be used in the fresh-cut industry. The use of combined methods to replace and/or reduce the use of chlorine is also reviewed.     

Recovery of Campylobacter jejuni from surfaces of poultry slaughterhouses after cleaning and disinfection procedures: analysis of a potential source of carcass contamination

Campylobacters are a primary cause of human bacterial enteritis worldwide. They are usually considered susceptible to the disinfectant molecules used in the food industry. The purpose of this study was to see if campylobacters could survive cleaning and disinfection in poultry slaughterhouses and whether the strains recovered could contaminate carcasses during processing. Samples obtained from the environment before and after cleaning and disinfection (transport crates, processing equipment surfaces, scald tank water) and from birds (fresh droppings, neck skins) were collected during 7 investigations in 4 different slaughterhouses. Out of 41 samples collected, 30 Campylobacter jejuni strains were recovered from the surfaces of processing equipment before cleaning and disinfection procedures in three slaughterhouses and 9 C. jejuni out of 51 samples collected were found after cleaning. The study was then focused on one slaughterhouse to trace passage of the pathogen on poultry carcasses. The antimicrobial resistance phenotypes (P) (minimum inhibitory concentration, MIC) of the C. jejuni isolates collected in this slaughterhouse were determined. Nine phenotypes could be distinguished. Three of these were of interest as they were found in isolates recovered after cleaning and disinfection procedures. The genotypes (G) were determined by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) of isolates with one of the three phenotypes of interest. Clusters constructed by combining the phenotype and genotyping observations (PG type) were compared between isolates obtained after cleaning and disinfection, and isolates from droppings, neck skin and transport crate samples of slaughtered poultry flocks. Only one PG type of strain was recovered from surfaces after cleaning and disinfection and from neck skin samples but was also recovered from transport crates. Our findings indicate that C. jejuni is able to survive overnight on food processing equipment surfaces, after cleaning and disinfection procedures, and that these strains may contaminate carcasses during the slaughter process. These results add to our understanding of poultry carcass contamination and highlight the need to develop ways of reducing the risk of human infection with Campylobacter through the consumption of poultry products.     

合流制排水系统溢流污水消毒处理

采用粪大肠杆菌群数≤10000个/L作为污水消毒的卫生学指标,以合流制雨水泵站的雨污混合水为原水,采用氧化性消毒处理法进行消毒实验.结果表明,达到合流制排水系统污水溢流紧急消毒要求的几种氧化性消毒剂最佳投加量(均以有效氯计)为:次氯酸钠30 mgCl/L,次氯酸钙25 mgCl/L,二氧化氯20 mgCl/L.相同条件下各氧化性消毒剂的优先次序为:二氧化氯>次氯酸钙>次氯酸钠>双氧水.     

4种常用蔬菜清洗剂对韭黄清洗后常温货架品质的影响

目的研究4种不同蔬菜清洗剂(过氧化氢、过氧乙酸、次氯酸钠和二氧化氯)对清洗后韭黄货架期品质的影响。方法通过比较4种清洗剂清洗后对韭黄货架过程中失重率、相对电导率、菌落总数和霉菌酵母数量、腐烂指数、总体感官值的变化情况,探讨不同清洗剂对韭黄货架品质的影响。结果 4种清洗剂对韭黄清洗后常温货架过程中各项测试指标影响差异显著(P0.05),其中100mg/L的过氧乙酸溶液和有效氯为100 mg/L的次氯酸钠溶液均能显著降低货架期韭黄失重率、组织电导率、菌落总数、霉菌和酵母数量、腐烂指数的升高,延缓韭黄总体感官质量的劣变,延长清洗后韭黄常温货架期至5 d左右。结论供试4种清洗剂均能不同程度的影响清洗后韭黄货架期品质变化,其中100mg/L的过氧乙酸溶液和有效氯为100mg/L的次氯酸钠溶液使用效果最优。     

Evaluation of the use of decontamination agents during fresh-cut leek processing and quantification of their effect on its total quality by means of a multidisciplinary approach

In this study the impact of different decontamination agents (water, peroxyacetic acid, sodium hypochlorite, neutral electrolyzed oxidizing water and gaseous chlorine dioxide) on the microbial and sensory quality as well as the nutrient content of minimally processed leek was investigated. Washing with 250 mg/L peroxyacetic acid and contact with 1.59 mg/L chlorine dioxide gas reduced the native microflora with 1.52 and 1.48 log cfu/g respectively whereas the other treatments did not induce a reduction that was significantly higher than the one achieved after washing with water. None of the treatments had a significant effect on the sensory quality of the raw fresh-cut leek, whereas a treatment with 200 mg/L sodium hypochlorite or with 250 mg/L peroxyacetic acid changed the sensory quality of cooked leek significantly when compared with water washing. Apart from the effect of leaching of nutrients into the wash water, the supplementary effect on nutrient content caused by adding a decontamination agent was limited with the exception of some isolated cases such as the significant losses of vitamin C (23%), tocopherols (11–18%) and violaxanthin (66%) after a treatment with respectively chlorine dioxide, 250 mg/L peroxyacetic acid and electrolyzed oxidizing water.Industrial relevanceVegetables like leek are highly contaminated with micro-organisms due to their contact with soil, water and other debris as a result of preharvest as well as postharvest conditions. Moreover, the sales of fresh-cut vegetables such as fresh-cut leek showed a tremendous increase over the last decade. Usually these products have a limited shelf-life due to microbial, sensorial and chemical alterations. The fresh-cut produce industry is continuously looking for treatments able to replace the traditionally used sodium hypochlorite which is associated with the formation of harmful disinfection by-products. In this study more innovative treatments like neutral electrolyzed oxidizing water, peroxyacetic acid and gaseous chlorine dioxide were studied for their effect on the microbial, sensory and nutritional quality of fresh-cut leek.     

过氧乙酸漂白的脱木素选择性

针对过氧乙酸脱木素选择性进行了研究:由二氧化氯、次氯酸盐和过氧乙酸漂白浆的卡伯值降低程度、黏度以及脱木素选择性综合分析可得,过氧乙酸漂白脱木素选择性略优于二氧化氯,明显优于次氯酸盐。     

BACTERICIDAL EFFICIENCIES OF COMMERCIAL DISINFECTANTS AGAINST LISTERIA MONOCYTOGENES ON SURFACES

The efficiencies of potassium persulphate, isopropanol, hydrogen peroxide and peracetic acid, quaternary ammonium compound, hypochlorite, sodium dichloroisocyanurate, ethanol and phenol derivatives, tertiary alkylamines and dimethyl alamine betaine-based disinfectants and a hypochlorite-based disinfecting cleaning agent were evaluated against eight Listeria monocytogenes strains representing three different ribotypes. All the disinfectants were effective in a suspension test with an exposure time of 30 s at the lowest concentrations recommended by the manufacturer. The efficiencies on surfaces were reduced. However, on clean surfaces all the agents were considered effective when the exposure time was 5 min and the concentration was the average recommended by the manufacturer. Five of nine disinfectants and the disinfecting cleaning agent were considered effective in soiled conditions in the surface test. The most efficient agent was isopropanol-based and the least effective was the disinfectant containing tertiary alkylamine and dimethyl alamine betaine. Differences in bactericidal efficiencies of disinfectants against different L. monocytogenes strains on meat soiled surfaces were found.     

Halonitroalkanes, halonitriles, haloamides, and N-nitrosamines: a critical review of nitrogenous disinfection byproduct formation pathways

Interest in the formation of nitrogenous disinfection byproducts (N-DBPs) has increased because toxicological research has indicated that they are often more genotoxic, cytotoxic, or carcinogenic than many of the carbonaceous disinfection byproducts (C-DBPs) that have been a focus for previous research. Moreover, population growth has forced utilities to exploit source waters impaired by wastewater effluents or algal blooms. Both waters feature higher levels of organic nitrogen, that might serve as N-DBP precursors. Utilities are exploring new disinfectant combinations to reduce the formation of regulated trihalomethanes and haloacetic acids. As some of these new combinations may promote N-DBP formation, characterization of N-DBP formation pathways is needed. Formation pathways for halonitroalkanes, halonitriles, haloamides, and N-nitrosamines associated with chlorine, ozone, chlorine dioxide, UV, and chloramine disinfection are critically reviewed. Several important themes emerge from the review. First, the formation pathways of the N-DBP families are partially linked because most of the pathways involve similar amine precursors. Second, it is unlikely that a disinfection scheme that is free of byproduct formation will be discovered. Disinfectant combinations should be optimized to reduce the overall exposure to toxic byproducts. Third, the understanding of formation pathways should be employed to devise methods of applying disinfectants that minimize byproduct formation while accomplishing pathogen reduction goals. Fourth, the well-characterized nature of the monomers constituting the biopolymers that likely dominate the organic nitrogen precursor pool should be exploited to predict the formation of byproducts likely to form at high yields.     

Cleaning in place with onsite‐generated electrolysed oxidizing water for water‐saving disinfection in breweries

The use of acid electrolysed water (AcEW) is a relatively new sanitizing technique for brewery equipment. Experiments showed that a 30% AcEW (a free chlorine concentration of above 17 mg/L) was a sufficient and effective alternative to conventional sanitizers such as peracetic acid (2%). On the basis of the results of industrial‐scale clean‐in‐place tests, an effective AcEW‐based clean‐in‐place procedure, which requires only 10 min of cleaning and does not require final water rinsing after sanitation, was established for the bright beer tank. Copyright © 2013 The Institute of Brewing & Distilling     

超声波与过氧乙酸的杀菌机制及在食品保鲜中的应用进展

果蔬、肉类、水产品等食品中微生物的生长繁殖会引起食品腐败变质,引发食品安全问题,造成经济损失与食物浪费。超声波作为一种绿色环保的非热加工技术,可利用空化效应消灭微生物。过氧乙酸是一种环境友好型的清洗剂,可作为含氯清洗剂的良好替代物。超声波与过氧乙酸均为环境友好型保鲜方式,二者联合使用在食品保鲜中具有巨大的应用潜力。本文就超声波、过氧乙酸单独使用或者二者联合处理的杀菌机制、对微生物生长的抑制作用、及在食品保鲜中的应用进行综述,并展望了未来的发展趋势,以期为新型绿色环保保鲜技术的创建与应用提供参考。     

饮用水中交链孢霉毒素氯消毒副产物鉴定及其毒性作用评价

目的 研究水中交链孢菌酮酸(TeA)和腾毒素(TEN)在氯消毒过程中的反应动力学特征,对产生的氯消毒副产物(DBPs)进行结构鉴定,并对其消毒副产物的细胞毒性进行初步探索。方法 本研究通过实验室模拟其消毒反应过程,研究其反应动力学特征,利用超高效液相色谱-串联四级杆飞行时间质谱(UPLC-Q-TOF/MS)和核磁共振波谱对反应产物进行结构鉴定并初步评价其毒性。结果 TeA氯消毒反应可生成2种氯消毒副产物DBP-188和DBP-240,而TEN氯代反应很慢未观察到氯消毒副产物的产生。反应动力学试验表明TEN与氯的反应速率随着反应体系中氯浓度和pH值的增加而升高。体外毒性预测分析发现TeA的氯消毒副产物经口毒性、发育毒性和致癌性均高于母体。结论 交链孢霉毒素经过氯消毒会产生氯消毒副产物,反应过程受pH值与氯浓度的影响,氯消毒副产物的预测毒性高于母体,细胞试验证明了TeA氯消毒副产物具有一定的细胞毒性。     

Comparison of byproduct formation in waters treated with chlorine and iodine: relevance to point-of-use treatment

Due to their efficacy in deactivating a range of microbial pathogens, particularly amoebic cysts, iodine-based disinfectants have been a popular option for point-of-use (POU) drinking water disinfection by campers, the military, and rural consumers in developing countries. Recently, concerns regarding the formation of cytotoxic and genotoxic iodinated disinfection byproducts (I-DBPs) have arisen during chloramine disinfection of iodide-containing waters in the developed world; similar concerns should pertain to iodine-based POU disinfection. Because there are alternative POU disinfection techniques, including chlorine-based disinfectants, this paper compared disinfection byproduct formation from a range of iodine-based disinfectants at their recommended dosages to chlorination and chloramination under overdosing conditions. Just as chloroform was the predominant trihalomethane (THM) forme during chlorination or chloramination, iodoform was the predominant THM formed during iodination. Conditions fostering THM formation were similar between these treatments, except that THM formation during chlorination increased with pH, while it was slightly elevated at circumneutral pH during iodination. Iodoform formation during treatment with iodine tincture was higher than during treatment with iodine tablets. On a molar basis, iodoform formation during treatment with iodine tincture was 20-60% of the formation of chloroform during chlorination, and total organic iodine (TOI) formation was twice that of total organic chlorine (TOCl), despite the 6-fold higher oxidant dose during chlorination. Based upon previous measurements of chronic mammalian cell cytotoxicity for the individual THMs, consumers of two waters treated with iodine tincture would receive the same THM-associated cytotoxic exposure in 4-19 days as a consumer of the same waters treated with a 6-fold higher dose of chlorine over 1 year. Iodoacetic acid, diiodoacetic acid, and other iodo-acids were also formed with iodine tincture treatment, but at levels <11% of iodoform. However, testing of a Lifestraw Personal POU device, which combines an iodinated anion exchange resin with activated carbon post-treatment, indicated minimal formation of I-DBPs and no iodine residual. Although N-nitrosamines have been associated with oxidant contact with anion exchange resins, N-nitrosamine formation rapidly declined to low levels (4 ng/L) using the Lifestraw device after the first few flushes of water.     

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.     

食品加工人员洗手消毒程序初探

目的验证现有洗手消毒程序能否满足动物违禁药物的消除。方法对含有动物违禁药物氯霉素的药膏进行全手涂抹实验和手部特定部位的涂抹实验,5人为一组,根据现有洗手消毒程序,分步骤进行,包括水洗、皂液洗、水洗、次氯酸钠浸泡、水洗和酒精喷涂,对每个步骤清洗后,利用棉签进行手部涂抹实验,对所获得的样本依据GB/T 22338-2008《动物源性食品中氯霉素类药物残留量测定》进行测定。结果在较高浓度下,现有的洗手消毒程序存在污染样品的可能。结论出口食品企业应注意洗手消毒程序的使用,尤其是手部涂抹药物的用药控制。     

Potentiation of the lethal effect of peroxygen on Bacillus cereus spores by alkali and enzyme wash

Bacillus cereus present in pipes and heat-exchangers represents a potential quality problem for dairy industry. The peroxygen-containing disinfectants investigated had only negligible sporicidal effect when applied at the recommended in-use temperature and concentration. However, cleaning agents used before disinfection potentiated their lethal activity. Pre-exposure of B. cereus spores to 1% sodium hydroxide at temperatures over 40 degrees C increased the sporicidal effect of the peroxygen-containing disinfectant. The effect was dependent on the alkali concentration and the temperature. Also, a significant potentiating activity of an enzyme-based cleaning agent was obtained, but the effect was smaller than for alkali treatment. The results indicated that disinfectants based on peroxygen can be used to eliminate B. cereus spores at non-corrosive temperatures and concentrations if the surfaces are cleaned with alkali or enzyme-based disinfectants prior to disinfection.     

Microbial and chemical characterization of commercial washing lines of fresh produce highlights the need for process water control

Process wash water and washed products from three different fresh produce processing lines were characterized at commercial scale. Different physicochemical and microbiological characteristics of wash water were measured. Great variability between processing lines on the physicochemical quality of process wash water was observed, caused in part by the type of produce washed. The relationship between lower aerobic mesophilic bacteria and higher free chlorine (FC) concentrations in wash water was detected (Pearson's correlation coefficient (PCC) = −0.53). Independently of the FC concentration, most of the water samples (>80%) showed presence of cultivable (limit of detection 1 CFU/100 mL), probably caused by the uncontrolled pH conditions. Higher values of FC and oxidation-reduction potential (ORP) in wash water were related to lower microbial load in washed produce (PCC = −0.82, and − 0.79, respectively). Higher concentration of chlorine was linked to a higher presence of disinfection by-products (DBPs) in the wash water, and washing in chlorinated water led to a significant increase in the concentration of DBPs in produce. However, the accumulation of trihalomethanes (THMs) in process wash water was not correlated with higher concentrations of these DBPs in produce.Industrial relevanceThe washing step of fresh produce processing lines is a critical process. The dose of disinfectants needs to be adequately optimized to avoid microbial contamination without generating the accumulation of disinfection by-products (DBPs). In this study, critical parameters that influence the efficacy of water disinfection and the occurrence of DBPs in fresh produce processing lines were identified under commercial conditions. The results evidenced that monitoring and control of pH play a critical role by maximizing the concentration of the most active form of chlorine in the water. The parameter UV254 measured on-line in the washing tank, can be suggested as a suitable indicator of the presence of organic matter in fresh produce wash water.     

Review--Persistence of Listeria monocytogenes in food industry equipment and premises

To understand why Listeria monocytogenes may persist in food industry equipment and premises, notably at low temperature, scientific studies have so far focused on adhesion potential, biofilm forming ability, resistance to desiccation, acid and heat, tolerance to increased sublethal concentration of disinfectants or resistance to lethal concentrations. Evidence from studies in processing plants shows that the factors associated with the presence of L. monocytogenes are those that favor growth. Interestingly, most conditions promoting bacterial growth were shown, in laboratory assays, to decrease adhesion of L. monocytogenes cells. Good growth conditions can be found in so-called harborage sites, i.e. shelters due to unhygienic design of equipment and premises or unhygienic or damaged materials. These sites are hard to eliminate. A conceptual model of persistence/no persistence based on the relative weight of growth vs. outcome of cleaning and disinfection is suggested. It shows that a minimum initial bacterial load is necessary for bacteria to persist in a harborage site and that when a low initial bacterial charge is applied, early cleaning and disinfection is the only way to avoid persistence. We conclude by proposing that there are no strains of L. monocytogenes with unique properties that lead to persistence, but harborage sites in food industry premises and equipment where L. monocytogenes can persist.     

二氧化氯对肉制品保鲜的研究

二氧化氯是一种有效的食品保鲜剂 ,目前在水处理、食品加工、保鲜等方面已得到广泛应用。试验研究了不同浓度二氧化氯对酱鸭的保鲜效果及其对酱鸭品质的影响。结果表明 ,酱鸭经浓度为 10 0～ 2 0 0mg/kg的二氧化氯溶液处理 2min后 ,常温下贮存 2 6～ 3 0d仍可保持较好的品质。