The microbiological safety of minimally processed vegetables

Summary Demand for fresh, convenient, minimally processed vegetables has led to an increase in the quantity and variety of products available to the consumer. Modified atmosphere packaging, in combination with refrigeration, is increasingly being employed as a mild preservation technique to ensure quality and storage-life. The fresh nature of these products, together with the mild processing techniques and subsequent storage conditions, have presented indigenous and pathogenic microorganisms with new ecosystems and potential infection vehicles; a number of outbreaks of foodborne disease being attributed to their consumption. Psychrotrophic pathogens and pathogens which are capable of maintaining an infectious potential under mild preservation regimes are of particular concern; Listeria monocytogenes , Aeromonas hydrophila and Clostridium botulinum being amongst the most notable. This review describes the processing, packaging and storage procedures involved in the production of minimally processed vegetables, and details their impact upon the survival and growth of associated pathogens. Gaps in our current understanding of the consequences of this novel technology for microbiological safety are highlighted.     

Effect of processing and storage conditions on the microbiological quality of minimally processed vegetables

The microbiological contamination of minimally processed vegetables was measured before and after processing and at different times and storage temperatures (5 and 10 days at 4 and 20 °C). To evaluate the efficacy of the overall process the water used for washing and rinsing the vegetables during the various phases of the operation were also examined. Thanks to the high quality of the vegetables at origin, simple chlorine treatment was sufficient to achieve a satisfactory reduction in coliforms, Escherichia coli, coliphages and saprophytic flora, thus ensuring that all of the freshly packed samples conformed to reference standards and guidelines. This conformity was maintained when the storage instructions indicated on the package (4 °C for 5 days) were followed. However, the persistence of faecal indicators after treatment suggested a potential risk of infection that could increase if the original contamination was higher. Microbiological examination of the water used for preliminary washing and for rinsing was seen to be useful in the assessment of the safety of the vegetables, at origin and after processing. The advantage of choosing coliphages for such monitoring is that they are indicators of viral contamination that can be measured rapidly. Critical points to be checked during the process are the levels of residual chlorine remaining in the washing tanks and the storage temperatures.     

食品安全的微生物学检验的质量控制

微生物能引起食物中毒和食源性传染病,因而是影响食品安全性的重要因素。食品微生物学检验的目的,就是为了监督食品生产和产品卫生质量,保障食品的食用安全。就目前实际工作中存在的问题,从基础质量控制、环节质量控制和结果质量控制等方面,讨论食品微生物学检验的质量控制。     

Irrigation water quality and microbial safety of leafy greens in different vegetable production systems: A review

Access to large sources of quality water for irrigation is fundamental to the hygienic cultivation of fresh produce. However, due to factors such as contamination of water bodies, access to clean uncontaminated water is fast becoming an ever increasing global challenge. The unavailability of quality source water increases the risk of contamination of fresh produce with human pathogenic microorganisms, which may compromise public health. Over the past few years, there has been a decline in the microbiological quality of surface water and other sources used for irrigation. This is mainly due to upstream fecal contamination. Therefore, the assessment and subsequent suitability of alternative water sources for irrigation such as roof-harvested rainwater should be considered. Contrasting views regarding the quality of roof-harvested rainwater (RHRW) have been published. Pathogens such as Salmonella and Campylobacter species and Listeria monocytogenes have been reported in RHRW. Leafy green vegetables such as cabbage, spinach, and lettuce are produced across a wide range of farming systems from regulated formal (commercial farms) to informal (small-scale and homestead gardens) setups. This review will discuss global water challenges associated with irrigation water, microbial quality of source water for irrigation, crop contamination, and pathogen detection and characterization methodologies.     

The microbiological conditions of carcasses from large game animals in Italy

This study investigates the microbiological conditions of large game animal carcasses following evisceration. Carcasses of animals (N=291) hunted in the Upper Susa Valley (Italian Alps) were analysed for pH, Aerobic Viable Count (AVC), Enterobacteriaceae, Yersinia spp., Listeria monocytogenes and Salmonella spp. After shooting, evisceration occurred within 60 min in 90.7% of animals and sampling within 90 min in 88.3% of animals. Mean pH values (5.97: ruminants; 5.77: wild boar) were similar to those of regularly slaughtered domestic species. AVC values were highest in animals shot in the abdomen. Within species, AVC and Enterobacteriaceae values did not differ across different shooting-evisceration/sampling times. However, these counts exceeded 5 and 2.5 log, respectively, in 18% of wild boar and 39% of ruminants; the highest values were detected in wild boar. No pathogens were detected in any species. These results reveal inadequate hygiene in game meat handling/harvesting, implicating the need for improved practices.     

Changes in vegetable microbiological quality introduced by processing methods

The main objective of this research was to investigate the effect in microbial quality of vegetables, because of the chain of buyers and sellers involved in the collection, processing and selling of vegetables, from the primary production sector up to the consumer level (from farm to table). Two processing plants and six hotels were selected and 240 vegetables, 30 vegetable containers, 18 water samples used for sanitation purposes and samples of 18 personnel's hands, were microbiologically analysed. Based on actual results and processing plants auditing, we conclude that initial vegetable microbial quality is critical. The storage, separation and packaging processes, cleaning procedures and retention time at processing plants can influence vegetable microbial quality. Buyers–sellers involved between vegetable production in primary sector and final consumer can offer a dramatic decrease in vegetable quality. The use of ISO 9001:2000 can improve product quality through techniques such as product traceability and resources management.     

Effect of lactic acid treatment during processing on the sensory quality and lactic acid content of fresh broiler chickens

Microbial decontamination by lactic acid treatment during processing of fresh broiler chickens is an effective way to produce a safer product with good keeping quality. It remained to be assessed whether such a treatment adversely affects the organoleptic quality of the product. Lactic acid treatment results in an increased acid concentration in the skin, with no increase in lactic acid concentration in the underlying muscle tissue. Differences in sensory quality were only found in appearance of the carcasses, the controls being identified as discoloured. A preference test did not show any difference in lactic acid treated and untreated grilled legs.     

调味品微生物学检验的质量控制

微生物能引起调味品霉变或腐败和带毒，进而造成食物中毒和食源性疾病，调味品微生物学检验的目的就是为了监督调味品生产，保障调味品的食用安全。本文就目前实际工作中存在的问题，从基础质量控制、环境质量控制和结果质量控制等方面，讨论调味品微生物检验的质量控制。     

Effect of irradiation and modified atmosphere packaging on the microbiological safety of minced pork stored under temperature abuse conditions

The safety of irradiated pork packed in 25% CO₂:75% N₂ and stored at abuse temperature (10 or 15°C) was assessed by inoculation studies involving Salmonella typhimurium, Listeria monocytogenes, Escherichia coli, Yersinia enterocolitica and Clostridium perfringens . Irradiation to a dose of 1.75 kGy reduced pathogen numbers to below the detection limit of 10² cells g^-1. When higher inoculum levels were used (10⁶ cells g^-1) irradiation at 1.75 kGy reduced pathogen numbers by 1 –>5 log₁₀ cycles depending on strain. Clostridium perfringens was the most resistant, and Y. enterocolitica the most sensitive of the pathogens studied.
In all cases when high numbers (10⁶ to 10⁷g^-1) of spoilage and/or pathogenic bacteria were present initially on the pork the meat appeared spoiled, and although irradiation reduced the number of microorganisms, the meat was still unacceptable from a sensory viewpoint after treatment.
It was concluded that the microbiological safety of irradiated, modified atmosphere packaged (MAP) pork is better than that of unirradiated MAP pork.     

食品微生物检验用培养基的使用及质量控制探讨

培养基自身质量的优劣、保存是否得当、配制使用是否正确都直接影响食品微生物检验结果的准确性。因此,加强培养基的质量控制和关注使用过程中的注意事项是保证检验准确性的关键。本文结合相关文献研究及笔者多年工作实践经验,对食品微生物检验用培养基在使用中的注意事项及质量控制措施进行了探讨,以供广大同行参考。实验室需结合工作实际选择合适的培养基质控标准、制定相应的质量控制作业指导书,对培养基进行理化指标和微生物指标的质量验收。此外,还要注意对培养基配制用水、生化鉴定试剂盒以及血清进行质量控制。实验室在使用培养基时要选择适宜的制备方法、灭菌方式、储存方式等,并按照标准要求进行质量控制,以保证最终检验结果的准确性。     

Effect of y‐radiation on chives safety and quality

The effect of γ‐irradiation on the quality of chives was evaluated. The samples were irradiated at 1.0 and 2.0 kGy, stored at 4 °C for 10 days and used for microbiological (aerobic mesophilic, moulds and yeasts, E. coli and Salmonella sp), biochemical (vitamin C and lipoperoxide (MDA) contents and superoxide dismutase (SOD) and guaiacol peroxidase (POX) activity) and sensorial evaluation. For irradiated samples, the total counts of aerobic mesophilic and moulds and yeasts showed a reduction of 6 log cycles during storage, and colour analysis showed no significant difference (P > 0.05) for the b*‐value. The contents of vitamin C were not significantly affected by irradiation and storage time. The MDA contents and SOD activity changed insignificantly at both γ‐irradiation levels after storage, while POX was significantly increased (P ≤ 0.05) at 1 kGy. Samples irradiated at 2.0 kGy presented sensorial acceptance after the storage. These results show that γ‐irradiation increases the shelf life of chives without significant changes in their quality.     

微生物感染对啤酒质量的影响

本文探讨了微生物感染对啤酒质量的影响，文中首先阐述了微生物感染的概念、啤酒生产中各工序可能感染微生物的种类及其对啤酒质量的影响，然后介绍了检测微生物感染的方法和防止感染的措施。     

食品微生物风险及国内外安全控制策略分析

食品安全关乎人们的身体健康和生命安全, 一旦发生食品安全恶性事件, 不但对居民日常生活造成较大影响, 同时也对中国的经济发展、国际形象和信任度造成一定损失。近年来突发的食品安全事件当中, 由微生物引发导致产生的事件比例和危害程度逐年升高, 如何防范并控制好食品微生物风险, 帮助食品相关产业和政府有关部门提升处置能力与风控意识, 持续增强卫生和风险管理能力, 具有非常重要的现实意义。本文介绍了食品微生物风险的研究背景与意义, 概述了微生物风险的控制原则与管理框架, 并对国内外食品安全方面的控制策略进行了探讨和研究。     

Effect of protease inhibitors from Adenanthera pavonia on the biochemical and microbiological quality of fishes

Fishes were given dip treatment in protease inhibitors extracted from Indian red wood seeds (Adenanthera pavonia) and their microbiological and biochemical characters were examined during storage at refrigerator temperatures. The results suggest that protease inhibitors bring about qualitative and quantitative changes in the microflora. Production of trimethylamine (TMA) and volatile bases appeared to be suppressed in the treated fishes. Incorporation of protease inhibitors in broth suppressed such activities as reduction of trimethylamine oxide, production of H₂ S and hydrolysis of gelatin in a significant proportion of bacterial cultures.     

借鉴国际经验完善我国食品安全风险监测制度的探讨

食品安全风险监测是在风险分析原则基础上,由国际组织倡导并在许多国家取得成功的一项食品安全风险管理工作。我国自2010年以来开始建立并实施国家食品安全风险监测制度,目前在建立制度、部门参与、计划和方案制定以及结果应用等方面还存在不少欠缺和不足。本文借鉴了国际组织和先进国家的经验,从风险监测的目的、特点和需求出发,提出了建立风险监测工作规划,进一步改进参与机制和信息沟通利用机制,并对食源性疾病监测工作提出了具体改进建议。     

营养安全视角下的食品加工应用研究

粮食和营养安全是当前全球关注的一项重要议题,预计到2050年全球人口将达到90亿,意味着需要通过继续增加粮食产量来解决日益复杂的粮食安全问题。与此同时减少从生产到消费整个供应链环节的食物损失浪费,以及通过食品加工为人类提高食品保存期限、营养质量以及食品安全也引起了极大的重视。本文通过文献梳理描述了初级食品生产系统的发展,以及食品加工对人类健康以及营养安全的作用。从未来的发展趋势来看,无论是农业生产部门还是食品加工部门都将面临用更少的资源来生产更多食品的问题。因而本文认为面对世界资源的日益紧张,必须对食品的能量和营养含量加以平衡,促进食品加工环节营养安全的提高,不失为一个良策。     

食前热水处理提高鲜切黄瓜微生物安全性的研究

探讨食前热水处理能否有效杀灭鲜切黄瓜表面的单增李斯特菌和鼠伤寒沙门氏菌这两种食源性致病菌,同时又保持其新鲜度。实验首先根据热水处理后鲜切黄瓜的感官品质,筛选了其耐热条件,进一步研究了热处理对水中和鲜切黄瓜表面食源性致病菌降低的效果。结果表明,经60℃ 5min热水处理,鲜切黄瓜上的鼠伤寒沙门氏菌、单增李斯特菌数量从高起始染菌浓度5.42、5.16log CFU/g,降低到检测线(0.6log CFU/g)以下,鲜切黄瓜的抗氧化值降低、细胞膜透性有所提高,但其测定硬度变化不大,感官上仍鲜脆,仍具有较好食用价值。      

Microbiological safety and quality of Mozzarella cheese assessed by the microbiological survey method

Dairy products are characterized by reduced shelf life because they are an excellent growth medium for a wide range of microorganisms. For this reason, it is important to monitor the microbiological quality of dairy products and, in particular, the total viable count and concentration of Escherichia coli, as they are indicators of the hygienic state of these products. In addition, in dairy products such as Mozzarella cheese, it is important to monitor the concentration of lactic acid bacteria (LAB), as they are the major components of starter cultures used in cheese production, contributing to the taste and texture of fermented products and inhibiting food spoilage bacteria by producing growth-inhibiting substances. For these reasons, to ensure the quality and safety of their products, cheese makers should monitor frequently, during fresh cheese production, the concentration of LAB and spoilage bacteria. However, usually, small- to medium-size dairy factories do not have an internal microbiological laboratory and external laboratories of analysis are often too expensive and require several days for the results. Compared with traditional methods, the microbiological survey (MBS) method developed by Roma Tre University (Rome, Italy) allows faster and less-expensive microbiological analyses to be conducted wherever they are necessary, without the need for a microbiological laboratory or any instrumentation other than MBS vials and a thermostat. In this paper, we report the primary validation of the MBS method to monitor LAB concentration in Mozzarella cheese and the analysis, using the MBS method, of total viable count, E. coli, and LAB concentrations in the production line of Mozzarella cheese as well as during the shelf life of the product stored at 20°C. The results obtained indicate that the MBS method may be successfully used by small- to medium-size dairy factories that do not have an internal microbiological laboratory. Using the MBS method, these dairy factories can monitor autonomously the microbiological safety and quality of their products, saving both time and money.     

The effect of hot-water immersions on the appearance and microbiological quality of skin-on chicken-breast pieces

Summary Immersion in hot water is one of many potential methods for reducing levels of pathogenic bacteria on the surface of poultry meat. However, if the meat is to be sold in the raw state reductions in microbiological numbers need to be achieved without changing the appearance of the meat. Samples of vacuum-packed skin-on chicken breast were immersed in hot water for a range of temperatures and times. Samples were then water cooled to arrest further heating. The final appearance of the samples was assessed visually and instrumentally with a chroma meter. Surface and internal temperatures were also measured. From this series of initial experiments a range of maximum temperature–time treatments were identified that would not cause unacceptable changes to surface appearance. Microbiological tests were then conducted on samples inoculated with a nalidixic acid resistant strain of Escherichia coli serotype O80 subjected to these treatments. The results showed that determining changes to the appearance of skin from samples by using a chroma meter was difficult. The changes caused to the samples by heat treatment were initially textural rather than colourimetric and thus could be identified visually but not instrumentally with a chroma meter. Visual changes were found for immersion times greater than 120 s at 50 °C, 60 s at 60 °C, 9 s at 70 °C, 6 s at 80 °C, 2 s at 90 °C and 1 s at 100 °C. The average temperatures measured on the surface after 2 s immersion at 90 °C and after 60 s at 60 °C were 20.5 °C and 54.8 °C, respectively. No reductions in counts of E. coli serotype O80 were measured on samples treated under these conditions. The results indicate that there is no immersion heat treatment (below 90 °C) capable of reducing contamination with E. coli , or similar thermotolerant microorganisms, on poultry without causing adverse changes in the product.