Potentially toxigenic fungi from selected grains and grain products

A total of 85 grain and grain product samples (including corn meal, corn muffin mix, popcorn, various types of rice, and self‐rising, all‐purpose unbleached and whole wheat flour) from U.S. retail were tested for fungal contamination levels and profiles using conventional plating as well as molecular methods. The results of this study showed that over 90% of wheat flour and corn product samples and 73% of rice samples tested carried live fungi. Popcorn carried the highest fungal levels reaching 5.45 log₁₀ colony forming units (cfu) per gram followed by corn meal (reaching 5.38 log₁₀ cfu/g). Mold and yeast counts in rice and wheat flour reached 3.30 log₁₀ and 3.28 log₁₀ cfu/g, respectively. The predominant molds in wheat flour were aspergilli and fusaria found in 50 and 46% of samples, respectively; Fusarium spp. were the most frequent contaminants of corn‐based products found in 74% of the samples followed by penicillia (present in 44% of tested samples). Rice, conversely, contained mainly Aspergillus, Fusarium, and yeasts (each found in 21% of the samples).

Practical applications

Toxigenic molds are often contaminating stored grains and grain products and under improper storage conditions could cause spoilage of these commodities accompanied with production of toxic secondary metabolites, mycotoxins. Mycotoxins are known to cause illnesses in humans and animals. Therefore, monitoring the presence and inhibiting the growth of these organisms is critical for achieving and maintaining high quality products, suitable for human and animal consumption, and free of health hazards. Establishing toxigenic mold profiles in stored grains and their derivatives can point to correct storage management and thus reduction/elimination of spoilage and mycotoxin production in these products. In this study we tested several corn, rice, and wheat flour commodities for live potentially toxigenic fungal species. Our findings can help select proper storage management techniques for these commodities.     

A Review on Aflatoxin Contamination and Its Implications in the Developing World: A Sub-Saharan African Perspective

Mycotoxins contamination in some agricultural food commodities seriously impact human and animal health and reduce the commercial value of crops. Mycotoxins are toxic secondary metabolites produced by fungi that contaminate agricultural commodities pre- or postharvest. Africa is one of the continents where environmental, agricultural and storage conditions of food commodities are conducive of Aspergillus fungi infection and aflatoxin biosynthesis. This paper reviews the commodity-wise aetiology and contamination process of aflatoxins and evaluates the potential risk of exposure from common African foods. Possible ways of reducing risk for fungal infection and aflatoxin development that are relevant to the African context. The presented database would be useful as benchmark information for development and prioritization of future research. There is need for more investigations on food quality and safety by making available advanced advanced equipments and analytical methods as well as surveillance and awareness creation in the region.     

A recent review of non‐biological remediation of aflatoxin‐contaminated crops

Aflatoxins are highly toxic, mutagenic, teratogenic and carcinogenic compounds produced predominantly as secondary metabolites by certain species of fungi belonging to the Aspergillus genus. Owing to the significant health risks and economic impacts associated with the presence of aflatoxins in agricultural commodities, a considerable amount of research has been directed at finding methods to prevent toxicity. This review compiles the recent literature of methods for the detoxification and management of aflatoxin in post‐harvest agricultural crops using non‐biological remediation. © 2013 Society of Chemical Industry     

The dry chain: Reducing postharvest losses and improving food safety in humid climates

BackgroundEven as increasing populations put pressure on food supplies, about one-third of the total food produced for human consumption is wasted, with the majority of loss in developing countries occurring between harvest and the consumer. Controlling product dryness is the most critical factor for maintaining quality in stored non-perishable foods. The high relative humidity prevalent in humid climates elevates the moisture content of dried commodities stored in porous woven bags, enabling fungal and insect infestations. Mycotoxins (e.g., aflatoxin) produced by fungi in insufficiently dried food commodities affect 4.5 billion people worldwide.Scope and approachWe introduce the term “dry chain” to describe initial dehydration of durable commodities to levels preventing fungal growth followed by storage in moisture-proof containers. This is analogous to the “cold chain” in which continuous refrigeration is used to preserve quality in the fresh produce industry. However, in the case of the dry chain, no further equipment or energy input is required to maintain product quality after initial drying as long as the integrity of the storage container is preserved. In some locations/seasons, only packaging is required to implement a “climate smart” dry chain, while in humid conditions, additional drying is required and desiccant-based drying methods have unique advantages.Key findings and conclusionsWe propose both climate-based and drying-based approaches to implement the dry chain to minimize mycotoxin accumulation and insect infestations in dry products, reduce food loss, improve food quality, safety and security, and protect public health.     

Aflatoxigenic fungi and mycotoxins in food: a review

Abstract

Food contamination is a common phenomenon in the production, distribution and consumption of processed and agricultural commodities all over the world. Food safety is now taking the frontal stage in food production, processing and distribution. This study assessed the presence of aflatoxigenic fungi and mycotoxins in foods, occurrence, control, socio-economic and health implications. This study also gave comprehensive information on the safety and mycological quality of foods as well the effect on the people and economy of various countries. The review revealed the various aflatoxigenic fungi in foods, their distribution in agricultural produce and their effects on reduction in yield and quality with attendant consumer health implications and resulting significant economic losses. In developing countries, majority of the people do not know the inherent dangers of consuming mouldy produce or food contaminated with fungi and moulds with possible contamination by mycotoxigenic fungi because of lack of awareness about the danger involved. In view of this, there is need for general and public education to sensitise the people on the economic and health hazards posed by mycotoxins. Control measures such as good agricultural practices, crop selection, proper washing and cooking practices of food commodities should be emphasized to the people. Regulatory control, fast and effective analyses and detection, good produce handling and storage should be encouraged as this will assist in mitigating the side effects of mycotoxins in foods particularly in the tropical and sub-tropical countries, and in Africa nations where there is enabling environment that promotes fungal growth, shortage of food and drought of modern storage and processing infrastructures.     

Specific antigen-based and emerging detection technologies of mycotoxins

Mycotoxins are secondary fungal metabolites produced by certain types of filamentous fungi or molds, such as Aspergillus, Fusarium, Penicillium, and Alternaria spp. Mycotoxins are natural contaminants of agricultural commodities, and their prevalence may increase due to global warming. According to the Food and Agriculture Organization of the United Nations, approximately 25% of the world's food crops are annually contaminated with mycotoxins. Mycotoxin-contaminated food and feed pose a high risk to both human and animal health. For instance, they possess carcinogenic, immunosuppressive, hepatotoxic, nephrotoxic, and neurotoxic effects. Hence, various approaches have been used to assess and control mycotoxin contamination. Significant challenges still exist because of the complex heterogeneous nature of food and feed composition. The potential of antigen-based approaches, such as enzyme-linked immunosorbent assay, flow injection immunoassay, chemiluminescence immunoassay, lateral flow immunoassay, and flow-through immunoassay, would contribute to our understanding about mycotoxins' rapid identification, their isolation, and the basic principles of the detection technologies. Additionally, we address other emerging technologies of potential application in the detection of mycotoxins. The data included in this review focus on basic principles and results of the detection technologies and would be useful as benchmark information for future research. © 2019 Society of Chemical Industry     

Advances in Mycotoxin Research: Public Health Perspectives

Aflatoxins, ochratoxins, fumonisins, deoxynivalenol, and zearalenone are of significant public health concern as they can cause serious adverse effects in different organs including the liver, kidney, and immune system in humans. These toxic secondary metabolites are produced by filamentous fungi mainly in the genus Aspergillus, Penicillium, and Fusarium. It is challenging to control the formation of mycotoxins due to the worldwide occurrence of these fungi in food and the environment. In addition to raw agricultural commodities, mycotoxins tend to remain in finished food products as they may not be destroyed by conventional processing techniques. Hence, much of our concern is directed to chronic health effects through long‐term exposure to one or multiple mycotoxins from contaminated foods. Ideally risk assessment requires a comprehensive data, including toxicological and epidemiological studies as well as surveillance and exposure assessment. Setting of regulatory limits for mycotoxins is considered necessary to protect human health from mycotoxin exposure. Although advances in analytical techniques provide basic yet critical tool in regulation as well as all aspects of scientific research, it has been acknowledged that different forms of mycotoxins such as analogs and conjugated mycotoxins may constitute a significant source of dietary exposure. Further studies should be warranted to correlate mycotoxin exposure and human health possibly via identification and validation of suitable biomarkers.     

Filamentous Fungi and Mycotoxins in Cheese: A Review

Important fungi growing on cheese include Penicillium, Aspergillus, Cladosporium, Geotrichum, Mucor, and Trichoderma. For some cheeses, such as Camembert, Roquefort, molds are intentionally added. However, some contaminating or technological fungal species have the potential to produce undesirable metabolites such as mycotoxins. The most hazardous mycotoxins found in cheese, ochratoxin A and aflatoxin M1, are produced by unwanted fungal species either via direct cheese contamination or indirect milk contamination (animal feed contamination), respectively. To date, no human food poisoning cases have been associated with contaminated cheese consumption. However, although some studies state that cheese is an unfavorable matrix for mycotoxin production; these metabolites are actually detected in cheeses at various concentrations. In this context, questions can be raised concerning mycotoxin production in cheese, the biotic and abiotic factors influencing their production, mycotoxin relative toxicity as well as the methods used for detection and quantification. This review emphasizes future challenges that need to be addressed by the scientific community, fungal culture manufacturers, and artisanal and industrial cheese producers.     

赭曲霉素A污染及毒性研究进展

赭曲霉素A(Ochratoxin A)是曲霉属和青霉属一些产毒菌株次级代谢产物,是一种重要食品污染物,具有强烈肾毒性和一定肝毒性、神经毒性及免疫毒性,并具有致癌、致畸、致突变性。该文介绍赭曲霉素常见产生菌及其对食品污染,毒理学特性及检测方法。     

Effect of Zingiber officinale Roscoe essential oil in fungus control and deoxynivalenol production of Fusarium graminearum Schwabe in vitro

ABSTRACT

Members of the Fusarium genus are capable of contaminating agricultural commodities, compromising the quality of maize and other grains, which leads to severe quality and yield losses. Contamination with mycotoxins is also a concern. Essential oils are possible alternatives to the use of synthetic pesticides for control of fungal contamination, as many have antifungal and anti-mycotoxigenic properties and are innocuous to human health. They also do not cause any sort of microbial resistance and do not promote environmental pollution. The aim of this study was to evaluate the antifungal and anti-mycotoxigenic effects of Zingiber officinale Roscoe essential oil (GEO) upon Fusarium graminearum Schwabe in vitro. The essential oil was extracted by hydrodistillation and analysed by GC/MS. Antifungal and anti-mycotoxigenic activities were assessed by HPLC/UV by quantifying ergosterol and deoxynivalenol (DON), respectively. Results indicated that GEO inhibited ergosterol production at a concentration of 1000 µg/mL and DON production at a concentration of 500 µg/mL, evidencing that the anti-mycotoxigenic effect is independent of the antifungal effect due to its probable direct action upon toxin biosynthesis.     

Effect of Arnebia hispidissima and Echium rauwolfii ethanolic root extracts on growth, forage quality and two rhizospheric soil fungi of pigeonpea

The boraginaceous plants produce a number of valuable metabolites in their roots used in folk medicine. Some of these metabolites are colored and restricted to the epidermal root tissue. The functional attributes of these metabolites to the plant may be related to resistance against microbes. The effect of the root extracts of Arnebia hispidissima (Ar) and Echium rauwolfii (Ech) on growth and some metabolic traits of pigeonpea as well as their effect on two rhizospheric fungi was studied. The ethanolic root extract of both plants did not result in remarkable changes in the morphological characters of pigeonpea plants. The treatments decreased the fresh weight but increased the dry weight. The relative water contents of the leaves were increased upon treatments with Ech or Ar root extracts. The physiological parameters such as chlorophyll content, protein and carbohydrates were greatly affected by the roots extracts. Ech root extract has better increasing effect on these metabolites compared to Ar root extract. Both root extracts reduced variably the number of colonies of rhizospheric fungi Fusarium oxysporum and Thanatephorus cucumeris. They increased the fungal cell death within 12 h in vitro and caused increase in electrolyte leakage of the fungal cells suggesting that they have some compounds which targeting the cell membrane. The results indicated that the boraginaceous root extracts can improve the nutritional characteristics of pigeonpea as a fodder and may protect the plant against microbial pathogens.     

Multiplex real-time PCR for detection and quantification of mycotoxigenic Aspergillus, Penicillium and Fusarium

The most agriculturally and economically important classes of mycotoxins are produced by species of Aspergillus, Penicillium, and Fusarium. Rapid methods to detect mycotoxigenic fungi could help prevent mycotoxins from entering the food chain. The purpose of this research was to develop a multiplex real-time PCR assay to detect and quantify multiple species of mycotoxigenic fungi. A pair of broad-spectrum PCR primers was designed for amplification of the internal transcribed spacer (ITS) regions of rDNA from the mycotoxigenic species. An in silico analysis of the primers revealed the presence of amplification in more than 40 Aspergillus species, 23 Fusarium species, and 32 Penicillium species as well as 64 other fungal genera. Genus-specific Taqman probes were designed from the ITS sequences of the most important mycotoxigenic species of Fusarium, Penicillium, and Aspergillus. The specificity of the probes was established against a wide range of fungal species. As a multiplex assay, the linear range of detection was 1 pg to 10 ng of DNA. The assay was validated by analyzing fungal growth in distiller's grain (DG), an animal feedstock that is a by-product when ethanol is produced from corn. This assay could be used as an initial step to evaluate the mycotoxigenic potential of DG and various other agricultural commodities.     

Mycotoxin problem in Africa: current status, implications to food safety and health and possible management strategies

Mycotoxins are toxic secondary metabolites of fungal origin and contaminate agricultural commodities before or under post-harvest conditions. They are mainly produced by fungi in the Aspergillus, Penicillium and Fusarium genera. When ingested, inhaled or absorbed through the skin, mycotoxins will cause lowered performance, sickness or death on humans and animals. Factors that contribute to mycotoxin contamination of food and feed in Africa include environmental, socio-economic and food production. Environmental conditions especially high humidity and temperatures favour fungal proliferation resulting in contamination of food and feed. The socio-economic status of majority of inhabitants of sub-Saharan Africa predisposes them to consumption of mycotoxin contaminated products either directly or at various points in the food chain. The resulting implications include immuno-suppression, impaired growth, various cancers and death depending on the type, period and amount of exposure. A synergistic effect between mycotoxin exposure and some important diseases in the continent such as malaria, kwashiorkor and HIV/AIDS have been suggested. Mycotoxin concerns have grown during the last few decades because of their implications to human and animal health, productivity, economics of their management and trade. This has led to development of maximum tolerated limits for mycotoxins in various countries. Even with the standards in place, the greatest recorded fatal mycotoxin-poisoning outbreak caused by contamination of maize with aflatoxins occurred in Africa in 2004. Pre-harvest practices; time of harvesting; handling of produce during harvesting; moisture levels at harvesting, transportation, marketing and processing; insect damage all contribute to mycotoxin contamination. Possible intervention strategies include good agricultural practices such as early harvesting, proper drying, sanitation, proper storage and insect management among others. Other possible interventions include biological control, chemical control, decontamination, breeding for resistance as well as surveillance and awareness creation. There is need for efficient, cost-effective sampling and analytical methods that can be used for detection analysis of mycotoxins in developing countries.     

Fungal and bacterial metabolites in commercial poultry feed from Nigeria

Metabolites of toxigenic fungi and bacteria occur as natural contaminants (e.g. mycotoxins) in feedstuffs making them unsafe to animals. The multi-toxin profiles in 58 commercial poultry feed samples collected from 19 districts in 17 states of Nigeria were determined by LC/ESI–MS/MS with a single extraction step and no clean-up. Sixty-three (56 fungal and seven bacterial) metabolites were detected with concentrations ranging up to 10,200?µg?kg^-1 in the case of aurofusarin. Fusarium toxins were the most prevalent group of fungal metabolites, whereas valinomycin occurred in more than 50% of the samples. Twelve non-regulatory fungal and seven bacterial metabolites detected and quantified in this study have never been reported previously in naturally contaminated stored grains or finished feed. Among the regulatory toxins in poultry feed, aflatoxin concentrations in 62% of samples were above 20?µg?kg^?1, demonstrating high prevalence of unsafe levels of aflatoxins in Nigeria. Deoxynivalenol concentrations exceeded 1000?µg?kg^?1 in 10.3% of samples. Actions are required to reduce the consequences from regulatory mycotoxins and understand the risks of the single or co-occurrence of non-regulatory metabolites for the benefit of the poultry industry.     

Fumonisins and their analogues in contaminated corn and its processed foods – a review

ABSTRACT

One of the food security problems faced worldwide is the occurrence of mycotoxins in grains and their foods. Fumonisins (FBs) are mycotoxins which are prevalent in corn (Zea mays L.) and its based foods. Their intake and exposure have been epidemiologically and inconclusively associated with oesophageal cancer and neural tube defects in humans, and other harmful health effects in animals. The toxic effects of FBs can be acute or chronic and these metabolites bioaccumulate mainly in liver and kidney tissues. Among FBs, fumonisin B₁ (FB₁) is the most relevant moiety although the ‘hidden’ forms produced after food thermal processes are becoming relevant. Corn is the grain most susceptible to Fusarium and FBs contamination and the mould growth is affected both by abiotic and biotic factors during grain maturation and storage. Mould counts are mainly affected by the grain water activity, the environmental temperature during grain maturation and insect damage. The abiotic factors affected by climatic change patterns have increased their incidence in other regions of the world. Among FBs, the hidden forms are the most difficult to detect and quantify. Single or combined physical, chemical and biological methods are emerging to significantly reduce FBs in processed foods and therefore diminish their toxicological effects.     

In vitro experimental environments lacking or containing soil disparately affect competition experiments of Aspergillus flavus and co-occurring fungi in maize grains

In vitro experimental environments are used to study interactions between microorganisms, and to predict dynamics in natural ecosystems. This study highlights that experimental in vitro environments should be selected to match closely the natural environment of interest during in vitro studies to strengthen extrapolations about aflatoxin production by Aspergillus and competing organisms. Fungal competition and aflatoxin accumulation were studied in soil, cotton wool or tube (water-only) environments, for Aspergillus flavus competition with Penicillium purpurogenum, Fusarium oxysporum or Sarocladium zeae within maize grains. Inoculated grains were incubated in each environment at two temperature regimes (25 and 30°C). Competition experiments showed interaction between the main effects of aflatoxin accumulation and the environment at 25°C, but not so at 30°C. However, competition experiments showed fungal populations were always interacting with their environments. Fungal survival differed after the 72-h incubation in different experimental environments. Whereas all fungi incubated within the soil environment survived, in the cotton wool environment none of the competitors of A. flavus survived at 30°C. With aflatoxin accumulation, F. oxysporum was the only fungus able to interdict aflatoxin production at both temperatures. This occurred only in the soil environment and fumonisins accumulated instead. Smallholder farmers in developing countries face serious mycotoxin contamination of their grains, and soil is a natural reservoir for the associated fungal propagules, and a drying and storage surface for grains on these farms. Studying fungal dynamics in the soil environment and other environments in vitro can provide insights into aflatoxin accumulation post-harvest.