Occurrence,prevention and remediation of toxigenic fungi and mycotoxins in silage: a review

Ruminants are considered to be less sensitive towards mycotoxins than monogastric animals because rumen microbiota have mycotoxin‐detoxifying capacities. Therefore the effect of mycotoxins towards ruminants has been studied to a lesser extent compared with monogastric animals. Worldwide, a high proportion of the ruminant diet consists of silages made of forage crops (i.e. all parts of the crop above the stubble are harvested). In practice, silages are often contaminated with multiple mycotoxins. Exposure to a cocktail of mycotoxins can hamper animal production and have severe health consequences. In this article the different aspects associated with mycotoxin contamination of silage are reviewed ‘from seed to feed’. An overview is given on the occurrence of toxigenic fungal species and their concomitant mycotoxins in forage crops before and after ensiling. The mycotoxin load of visually non‐mouldy samples and mouldy hot spots within the same silo is also compared. Subsequently, this review delves into different problem‐solving strategies. A logical first step is prevention of mould growth and mycotoxin production in the field, during harvest and during ensiling. If prevention should fail, several remediation strategies are available. These are listed, mainly focusing on the possibilities of microbial degradation of mycotoxins in vivo in silage. © 2015 Society of Chemical Industry     

中国谷物真菌毒素污染研究现状

谷物易受多种真菌毒素污染且消费量巨大，是人畜真菌毒素的主要摄入来源。本文统计了2009年至今关于我国谷物中真菌毒素污染的研究报道，发现国内的研究大多集中在水稻、小麦和玉米，而杂粮作物少之又少。其中，水稻受真菌毒素污染情况较轻；小麦主要受镰刀菌毒素污染，尤其是脱氧雪腐镰刀菌烯醇和玉米赤霉烯酮；玉米则易感染多种真菌毒素。此外，小杂粮薏米、燕麦、谷子和高粱也有不同程度的污染。为明确谷物质量安全隐患，有效缓解谷物中真菌毒素的污染，我们应进一步加强对重要杂粮作物中真菌毒素的监管力度，建立更全面的真菌毒素筛查方法，建设真菌毒素防控标准化体系，强化农民对真菌毒素防控的意识与技术。     

食品中新兴真菌毒素检测技术及其污染现状研究进展

真菌毒素是由曲霉菌、青霉菌和镰刀菌等丝状真菌在适当的环境条件下产生的有毒次生代谢产物，是谷物、水果、坚果等食品中常见的污染物，可引起广泛的毒性效应，主要表现为致癌性、致突变性、肝毒性、肾毒性、免疫毒性、神经毒性、致畸性等，对人类和动物的健康构成威胁。近些年来，由于自然气候的改变及检测技术的创新发展，一些新出现的真菌毒素逐渐引起大家的广泛关注，如已报道的交链孢毒素、新兴镰刀菌毒素等。这些尚未得到监管，并且如何产生、浓度水平和毒理数据有限的真菌毒素被定义为“新兴”真菌毒素。本文综述了两大类12种新兴毒素的结构性质、检测分析技术进展及在食品中的污染状况，以期为真菌毒素污染的全面评估及防控提供思路。     

果蔬及其制品真菌毒素的控制研究进展

真菌毒素是真菌在生长过程中所产生的一些次级代谢产物,广泛存在于谷物和饲料中,对人畜健康危害极大。近年研究表明果蔬在采后与加工环节中也易污染真菌毒素,已经引起了公众的广泛关注。本文主要从物理方法、化学方法、生物方法等方面综述了果蔬及其产品中真菌毒素控制方法的研究进展,其中生物防治果蔬及其产品中真菌毒素的方法由于安全、高效及环境友好,具有潜在的应用前景。      

Decontamination and detoxification strategies for the Fusarium mycotoxin deoxynivalenol in animal feed and the effectiveness of microbial biodegradation

Trichothecenes are a group of mycotoxins mainly produced by fungi of the Fusarium genus. Deoxynivalenol (DON) is one of the most abundant and important trichothecenes in food and feed, and is a significant contaminants due to its frequent occurrence in toxicologically relevant concentrations worldwide. Since toxin production depends strongly on environmental conditions, such as temperature and humidity, Fusarium toxin contamination can not be avoided completely. Therefore, exposure to this toxin is a permanent health risk for both humans and farm animals. As cereal crops are commonly contaminated with DON and animal diets consist mainly of cereals, it can be assumed that animals are frequently exposed to DON-contaminated feeds. Many strategies can be undertaken to reduce the toxic effect of DON. In addition to the general necessity for minimizing all risk factors that might influence the contamination of cereals with DON, such as the so-called field toxins before harvest, several post-harvest strategies can be applied to counteract possible deleterious effects of this mycotoxin in farm animals. Another approach for decontamination in feedstuffs is the use of adsorbent materials. Adsorbent materials may bind mycotoxins in the gastrointestinal tract and reduce absorption and systemic toxicity. It has been shown that some adsorbents are suitable to alleviate the toxic effects of specific mycotoxins, but its efficacy against trichothecenes is practically zero. Therefore, alternative strategies to reduce animal and human health risk are needed. The use of microbial additives is a method which uses microorganisms having the capability to detoxify mycotoxins by metabolism or degradation prior to their resorption in the gastrointestinal tract. DON has been reported to be completely transformed to de-epoxy-DON by ruminal and intestinal microflora. Eubacterium BBSH 797 was capable of DON degradation and counteracted the toxic effects of DON in animals. This review focuses on the efficacy of microbial feed additives in ameliorating the toxic effects of DON. According to the results of experiments to date, it appears that microorganisms are the main living organisms suitable for this mycotoxin biodegradation. However, the use of this approach depends on its effectiveness from both a practical and economic perspective.     

Strategies to reduce mycotoxin levels in maize during storage: a review

Maize (Zea mays L.) is one of the main cereals as a source of food, forage and processed products for industry. World production is around 790 million tonnes of maize because as a staple food it provides more than one-third of the calories and proteins in some countries. Stored maize is a man-made ecosystem in which quality and nutritive changes occur because of interactions between physical, chemical and biological factors. Fungal spoilage and mycotoxin contamination are of major concern. Aspergillus and Fusarium species can infect maize pre-harvest, and mycotoxin contamination can increase if storage conditions are poorly managed. Prevention strategies to reduce the impact of mycotoxin in maize food and feed chains are based on using a hazard analysis critical control point systems (HACCP) approach. To reduce or prevent production of mycotoxins, drying should take place soon after harvest and as rapidly as feasible. The critical water content for safe storage corresponds to a water activity (a _w) of about 0.7. Problems in maintaining an adequately low a _w often occur in the tropics where high ambient humidity make the control of commodity moisture difficult. Damage grain is more prone to fungal invasion and, therefore, mycotoxin contamination. It is important to avoid damage before and during drying, and during storage. Drying maize on the cob before shelling is a very good practice. In storage, many insect species attack grain and the moisture that can accumulate from their activities provides ideal conditions for fungal activity. To avoid moisture and fungal contamination, it is essential that the numbers of insects in stored maize should be kept to a minimum. It is possible to control fungal growth in stored commodities by controlled atmospheres, preservatives or natural inhibitors. Studies using antioxidants, essential oils under different conditions of a _w, and temperature and controlled atmospheres have been evaluated as possible strategies for the reduction of fungal growth and mycotoxin (aflatoxins and fumonisins) in stored maize, but the cost of these treatments is likely to remain prohibitive for large-scale use.     

Further mycotoxin effects from climate change

Climate change will affect mycotoxins in food. The 2007 Intergovernmental Panel on Climate Change report is reinterpreted herein to account for what may occur with mycotoxins. Warmer weather, heat waves, greater precipitation and drought will have various impacts, depending on which regions of the world and mycotoxin systems are considered. The humidity issues are more complex as some areas will experience drought and others greater precipitation: in vivo data on the effects of moisture on mycotoxins in crops are more ambiguous than those for temperature. In vitro data on fungal growth and mycotoxin production may not relate directly to the situation in the field or post harvest, but are useful for base-line assumptions. The effects of climate in various regions of the world, i.e. Africa, Europe, Asia, Latin America and North America are considered in terms of mycotoxin contamination. Crops introduced to exploit altered climate may be subject to fewer mycotoxin producing fungi (the “Parasites Lost” phenomenon). Increased mycotoxins and UV radiation may cause fungi to mutate on crops and produce different mycotoxins. Whereas there is relevant information on aflatoxins, deoxynivalenol, and ochratoxin A, more mycotoxins require to be considered: Data on patulin are missing. The current paper considers uniquely ergot alkaloids. Amelioration strategies are provided. There is considerable urgency in the need to address these issues.     

Silage review: Mycotoxins in silage: Occurrence,effects, prevention,and mitigation

Ensiled forage, particularly corn silage, is an important component of dairy cow diets worldwide. Forages can be contaminated with several mycotoxins in the field pre-harvest, during storage, or after ensiling during feed-out. Exposure to dietary mycotoxins adversely affects the performance and health of livestock and can compromise human health. Several studies and surveys indicate that ruminants are often exposed to mycotoxins such as aflatoxins, trichothecenes, ochratoxin A, fumonisins, zearalenone, and many other fungal secondary metabolites, via the silage they ingest. Problems associated with mycotoxins in silage can be minimized by preventing fungal growth before and after ensiling. Proper silage management is essential to reduce mycotoxin contamination of dairy cow feeds, and certain mold-inhibiting chemical additives or microbial inoculants can also reduce the contamination levels. Several sequestering agents also can be added to diets to reduce mycotoxin levels, but their efficacy varies with the type and level of mycotoxin contamination. This article gives an overview of the types, prevalence, and levels of mycotoxin contamination in ensiled forages in different countries, and describes their adverse effects on health of ruminants, and effective prevention and mitigation strategies for dairy cow diets. Future research priorities discussed include research efforts to develop silage additives or rumen microbial innocula that degrade mycotoxins.     

Post-harvest control strategies: minimizing mycotoxins in the food chain

Contamination of cereal commodities by moulds and mycotoxins results in dry matter, quality, and nutritional losses and represents a significant hazard to the food chain. Most grain is harvested, dried and then stored on farm or in silos for medium/long term storage. Cereal quality is influenced by a range of interacting abiotic and biotic factors. In the so-called stored grain ecosystem, factors include grain and contaminant mould respiration, insect pests, rodents and the key environmental factors of temperature, water availability and intergranular gas composition, and preservatives which are added to conserve moist grain for animal feed. Thus knowledge of the key critical control points during harvesting, drying and storage stages in the cereal production chain are essential in developing effective prevention strategies post-harvest. Studies show that very small amounts of dry matter loss due to mould activity can be tolerated. With <0.5% dry matter loss visible moulding, mycotoxin contamination and downgrading of lots can occur. The key mycotoxigenic moulds in partially dried grain are Penicillium verrucosum (ochratoxin) in damp cool climates of Northern Europe, and Aspergillus flavus (aflatoxins), A. ochraceus (ochratoxin) and some Fusarium species (fumonisins, trichothecenes) on temperate and tropical cereals. Studies on the ecology of these species has resulted in modelling of germination, growth and mycotoxin minima and prediction of fungal contamination levels which may lead to mycotoxin contamination above the tolerable legislative limits (e.g. for ochratoxin). The effect of modified atmospheres and fumigation with sulphur dioxide and ammonia have been attempted to try and control mould spoilage in storage. Elevated CO2 of >75% are required to ensure that growth of mycotoxigenic moulds does not occur in partially dried grain. Sometimes, preservatives based on aliphatic acids have been used to prevent spoilage and mycotoxin contamination of stored commodities, especially feed. These are predominantly fungistats and attempts have been made to use alternatives such as essential oils and anti-oxidants to prevent growth and mycotoxin accumulation in partially dried grain. Interactions between spoilage and mycotoxigenic fungi and insect pests inevitably occurs in stored grain ecosystems and this can further influence contamination with mycotoxins. Effective post-harvest management of stored commodities requires clear monitoring criteria and effective implementation in relation to abiotic and biotic factors, hygiene and monitoring to ensure that mycotoxin contamination is minimised and that stored grain can proceed through the food chain for processing.     

Food Safety and Increasing Hazard of Mycotoxin Occurrence in Foods and Feeds

The possible hazard of mycotoxin occurrence in foods and feeds and some food-borne mycotoxicoses is reviewed. Management of the risk of mycotoxin contamination using some useful preventive measures against mycotoxin contamination of foods/feeds during pre- and post-harvesting periods is considered. The physical and chemical methods of mycotoxin decontamination of foods/feeds are briefly described. The use of various feed additives as a method for prevention of the adverse effects of mycotoxins is reviewed. The processing of various foods and feeds is considered in a view to possible mycotoxin decontamination. The necessary hygiene control and risk assessment in regard to mycotoxin contamination of foods and feeds in addition to some useful prophylactic measures are briefly described. A short reference is made concerning the most successful methods of veterinary hygiene control in order to prevent a possible entering of some mycotoxins in commercial channels with a view to human health.     

食品与饲料基质中真菌毒素检测技术研究进展

真菌毒素是真菌在生长繁殖过程中产生的相对分子质量较小的次生有毒代谢产物,不易被加工或烹调加热所破坏,超过一定摄入量后会引起人的肝肾功能下降、癌变或诱发免疫抑制性疾病。目前尚无绝对有效的措施避免真菌毒素的污染,因此,研究可以准确高效地测定食品和饲料基质中的真菌毒素的检测技术非常重要。本研究通过对真菌毒素提取方法、净化方法及检测技术的研究进展进行综述,发现目前研究方法大多是针对某一种真菌毒素进行检测的常规检测方法或者同时检测多种真菌毒素的检测方法,由于这些方法存在稳定性差、定量不准确或前处理复杂等,因此未来应大力开发检测快速、高灵敏度、高特异性的真菌毒素检测方法。     

Mycotoxins in fruits,fruit juices,and dried fruits

This review gives an overview of the presence of mycotoxins in fruits. Although several mycotoxins occur in nature, very few (aflatoxins, ochratoxin A, patulin, Alternaria toxins) are regularly found in fruits. It has been shown that the presence of fungi on fruits is not necessarily associated with mycotoxin contamination. The formation of mycotoxins depends more on endogenous and environmental factors than fungal growth does. Mycotoxins may remain in fruits even when the fungal mycelium has been removed. Depending on the fruit and the mycotoxin, the diffusion of mycotoxins into the sound tissues of fruits may occur. The influence of the selection and storage of fruits and the influence of different processing steps involved in the production of fruit juices and dried fruits on possible mycotoxin contamination is described. It is shown that the careful selection, washing, and sorting of fruits is the most important factor in the reduction of mycotoxin contamination during the production of fruit juices. The processing of fruits does not result in the complete removal of mycotoxins.     

Mycotoxins in infant/toddler foods and breakfast cereals in the US retail market

The objective of this study was to conduct a mycotoxin survey of commercial infant/toddler foods (cereals and teething biscuits) and breakfast cereals in the United States. A total of 215 retail samples were collected from three geographical locations and analysed for aflatoxins, fumonisins, deoxynivalenol, HT-2 toxin, ochratoxin A, T-2 toxin, and zearalenone using a stable isotope dilution liquid-chromatography tandem mass spectrometry (LC-MS/MS) method. One or more mycotoxins were found in 69% (101/147) of the infant/toddler foods and 50% (34/68) of breakfast cereals. Mycotoxin co-occurrence was observed in 12% of infant/toddler foods and 32% of breakfast cereals. However, the concentrations of detected mycotoxins were lower than the current FDA action and guidance levels. Aflatoxins and HT-2 toxin were not detected in any of the samples, while deoxynivalenol was the most frequently detected mycotoxin. Rice-based cereals appeared to be less susceptible to mycotoxin contamination than other cereal types.     

粮食中隐蔽型真菌毒素污染的研究进展

真菌毒素污染是影响全球食品安全问题的重要因素之一。真菌毒素是真菌产生的次级代谢产物,对人体、动植物皆可产生危害。自然条件下,真菌毒素分子可与葡萄糖、丙二酸或谷胱甘肽等极性较强的基团结合,生成结合型真菌毒素。由于毒素结构发生改变,现有的常规检测手段不能有效地检测其存在,因此称其为隐蔽型真菌毒素(masked mycotoxins)。已有文献报道,隐蔽型真菌毒素往往与其原型同时存在于粮食中,而隐蔽型毒素在进入人和动物体内后,经水解、氧化还原等代谢过程,可释放出有毒的毒素原型分子,给食品安全、人和动物健康造成严重隐患。因此对隐蔽型真菌毒素的形成机制、污染状况和毒理研究应尽快展开。本文综述了国内外近几年以来几种常见隐蔽型真菌毒素的最新研究进展,为隐蔽型真菌毒素的研究提供有价值的参考。     

真菌毒素检测与限量标准的现状与问题分析

真菌毒素是一类由丝状真菌在适宜条件下产生的有毒次级代谢产物, 极易污染粮谷类食品、食用油及乳制品等, 具有肝毒性、肾毒性、致畸性、致癌性、免疫抑制及破坏生殖系统等毒性, 对人体危害极大, 是继农药残留、兽药残留、重金属污染后, 影响农产品质量安全的又一类关键风险因子, 极大的制约了我国农产品的出口贸易, 同时也造成了我国食品安全的又一问题。本文重点介绍了农产品中真菌毒素的类型品种、毒性特点以及不同检验方法的适用范围、限量及检出限, 阐述了真菌毒素限量标准的研究进展和标准内容, 通过比对国内外真菌毒素的研究种类和进展, 分析目前真菌毒素污染现状及存在的问题, 提出应对策略, 对真菌毒素污染检测的发展进行了展望, 对今后保障饮食安全提供科学依据。     

Strategies to prevent mycotoxin contamination of food and animal feed: a review

Mycotoxins are fungal secondary metabolites that have been associated with severe toxic effects to vertebrates produced by many important phytopathogenic and food spoilage fungi including Aspergillus, Penicillium, Fusarium, and Alternaria species. The contamination of foods and animal feeds with mycotoxins is a worldwide problem. We reviewed various control strategies to prevent the growth of mycotoxigenic fungi as well as to inhibit mycotoxin biosynthesis including pre-harvest (resistance varieties, field management and the use of biological and chemical agents), harvest management, and post-harvest (improving of drying and storage conditions, the use of natural and chemical agents, and irradiation) applications. While much work in this area has been performed on the most economically important mycotoxins, aflatoxin B(1) and ochratoxin A much less information is available on other mycotoxins such as trichothecenes, fumonisin B(1), zearalenone, citrinin, and patulin. In addition, physical, chemical, and biological detoxification methods used to prevent exposure to the toxic and carcinogenic effect of mycotoxins are discussed. Finally, dietary strategies, which are one of the most recent approaches to counteract the mycotoxin problem with special emphasis on in vivo and in vitro efficacy of several of binding agents (activated carbons, hydrated sodium calcium aluminosilicate, bentonite, zeolites, and lactic acid bacteria) have also been reviewed.     

Mycotoxin Contamination of Maize in China

China is a major cereal‐producing country and almost one third of the annual cereal yield is maize. The maize plant and kernel are prone to infection by fungal attack and are most likely to be contaminated with mycotoxins under suitable temperature and humidity conditions, during both the growing and storage period. A number of investigations conducted in China have demonstrated that maize had been infected by fungi and contaminated with mycotoxins to varying degrees. Although most of the maize produced in China is used as feed and raw materials for the chemistry industry, a small amount of maize is consumed directly by humans and the hazards of mycotoxin to humans cannot be ignored. The state of mycotoxin contamination of maize in China is analyzed in this review. Due to unfavorable weather and poor storage conditions, the high incidences of mycotoxin contamination of maize are of great concern to the Chinese. It is imperative for the national and local governments to increase investments on building large‐scale modern warehouses and instructing farmers to grow, harvest, and store maize safely. Meanwhile, due to accumulative toxic effects of mycotoxins, quality control should be enforced to guarantee that animal products are safe for human consumption.     

Pre‐ and Postharvest Strategies to Minimize Mycotoxin Contamination in the Rice Food Chain

Rice is part of many people's diet around the world, being the main energy source in some regions. Although fewer reports exist on the occurrence of mycotoxins in rice compared to other cereals, fungal contamination and the associated production of toxic metabolites, even at lower occurrence levels compared to other crops, are of concern because of the high consumption of rice in many countries. Due to the diversity of fungi that may contaminate the rice food chain, the co‐occurrence of mycotoxins is frequent. Specific strategies to overcome these problems may be applied at the preharvest part of the crop chain, while assuring good practices at harvest and postharvest stages, since different fungi may find suitable conditions to grow at the various stages of the production chain. Therefore, the aim of this review is to present the state‐of‐the‐art knowledge on such strategies in an integrated way, from the field to the final products, to reduce mycotoxin contamination in rice.     

真菌毒素的降解技术研究进展

真菌毒素是一类长期困扰粮食安全的重要污染物,尤其是对于谷物类作物具有极大的危害性,因此,对于真菌毒素的检测与降解已经成为粮食安全方面的重点攻克对象。根据现有的研究,主要的降解手段有物理法、化学法以及生物法等,此外还涌现出了多种手段协同作用降解的方式,种类呈现多样化的趋势。因此,为了进一步推进更加便捷、高效的真菌毒素降解方法应用到相关的粮食领域中,减少降解剂对食品本身品质的影响,并帮助开发新的真菌毒素降解方法。作者综述了近年来研究者在防控粮食等产品中各种真菌毒素污染所采用的不同策略,并且分析了相应的产毒机制,讨论了现阶段所采用的各种方法防控真菌毒素的优势和不足,同时展望了未来食品工业对真菌毒素降解方法的发展新趋势,提出了新的研究方向。     

Some major mycotoxins and their mycotoxicoses--an overview

Mycotoxins likely have existed for as long as crops have been grown but recognition of the true chemical nature of such entities of fungal metabolism was not known until recent times. Conjecturally, there is historical evidence of their presence back as far as the time reported in the Dead Sea Scrolls. Evidence of their periodic, historical occurrence exists until the recognition of aflatoxins in the early 1960s. At that time mycotoxins were considered as a storage phenomenon whereby grains becoming moldy during storage allowed for the production of these secondary metabolites proven to be toxic when consumed by man and other animals. Subsequently, aflatoxins and mycotoxins of several kinds were found to be formed during development of crop plants in the field. The determination of which of the many known mycotoxins are significant can be based upon their frequency of occurrence and/or the severity of the disease that they produce, especially if they are known to be carcinogenic. Among the mycotoxins fitting into this major group would be the aflatoxins, deoxynivalenol, fumonisins, zearalenone, T-2 toxin, ochratoxin and certain ergot alkaloids. The diseases (mycotoxicoses) caused by these mycotoxins are quite varied and involve a wide range of susceptible animal species including humans. Most of these diseases occur after consumption of mycotoxin contaminated grain or products made from such grains but other routes of exposure exist. The diagnosis of mycotoxicoses may prove to be difficult because of the similarity of signs of disease to those caused by other agents. Therefore, diagnosis of a mycotoxicoses is dependent upon adequate testing for mycotoxins involving sampling, sample preparation and analysis.