Key Global Actions for Mycotoxin Management in Wheat and Other Small Grains

Mycotoxins in small grains are a significant and long-standing problem. These contaminants may be produced by members of several fungal genera, including Alternaria, Aspergillus, Fusarium, Claviceps, and Penicillium. Interventions that limit contamination can be made both pre-harvest and post-harvest. Many problems and strategies to control them and the toxins they produce are similar regardless of the location at which they are employed, while others are more common in some areas than in others. Increased knowledge of host-plant resistance, better agronomic methods, improved fungicide management, and better storage strategies all have application on a global basis. We summarize the major pre- and post-harvest control strategies currently in use. In the area of pre-harvest, these include resistant host lines, fungicides and their application guided by epidemiological models, and multiple cultural practices. In the area of post-harvest, drying, storage, cleaning and sorting, and some end-product processes were the most important at the global level. We also employed the Nominal Group discussion technique to identify and prioritize potential steps forward and to reduce problems associated with human and animal consumption of these grains. Identifying existing and potentially novel mechanisms to effectively manage mycotoxin problems in these grains is essential to ensure the safety of humans and domesticated animals that consume these grains.

The fate of mycotoxins during secondary food processing of maize for human consumption

Mycotoxins are naturally occurring fungal metabolites that are associated with health hazards and are widespread in cereals including maize. The most common mycotoxins in maize that occur at relatively high levels are fumonisins (FBs), zearalenone, and aflatoxins; furthermore, other mycotoxins such as deoxynivalenol and ochratoxin A are frequently present in maize. For these toxins, maximum levels are laid down in the European Union (EU) for maize raw materials and maize-based foods. The current review article gives a comprehensive overview on the different mycotoxins (including mycotoxins not regulated by EU law) and their fate during secondary processing of maize, based on the data published in the scientific literature. Furthermore, potential compliance with the EU maximum levels is discussed where appropriate. In general, secondary processing can impact mycotoxins in various ways. Besides changes in mycotoxin levels due to fractionation, dilution, and/or concentration, mycotoxins can be affected in their chemical structure (causing degradation or modification) or be released from or bound to matrix components. In the current review, a special focus is set on the effect on mycotoxins caused by different heat treatments, namely, baking, roasting, frying, (pressure) cooking, and extrusion cooking. Production processes involving multiple heat treatments are exemplified with the cornflakes production. For that, potential compliance with FB maximum levels was assessed. Moreover, effects of fermentation of maize matrices and production of maize germ oil are covered by this review.

Thermal stability of T-2 and HT-2 toxins during biscuit- and crunchy muesli-making and roasting

The mycotoxins T-2 and HT-2 toxin are frequently occurring food contaminants which are produced by Fusarium species. Humans and animals are mainly exposed to these substances by the consumption of contaminated oats, maize and wheat. For the production of crunchy muesli, bread and bakery products, these cereals undergo multiple processing steps, including baking, roasting and extrusion cooking. However, the influence of food processing on T-2 and HT-2 toxin levels is to date poorly understood. Thus, the effects of baking and roasting on both mycotoxins were evaluated during biscuit-, crunchy muesli- and toasted oat flakes-production under precise variation of various parameters: heating time and temperature as well as recipe formulation were varied in the range they are applied in the food processing industry. Therefore, oatmeal or flaked oats were artificially contaminated individually with both toxins and processed at the laboratory scale. T-2 toxin generally showed a higher degradation rate than HT-2 toxin. During biscuit-making up to 45% of T-2 toxin and 20% of HT-2 toxin were thermally degraded, showing a dependency on water content, baking time and temperature. The preparation of crunchy muesli yielded no significant toxin degradation which is probably due to the low temperatures applied. Roasting led to a degradation of 32% of T-2 toxin and 24% of HT-2 toxin. Taken together, both mycotoxins are partially degraded during thermal food processing; the degradation rates are influenced by the food composition and processing parameters.

The Fate of Mycotoxins During the Processing of Wheat for Human Consumption

Mycotoxins are a potential health threat in cereals including wheat. In the European Union (EU), mycotoxin maximum levels are laid down for cereal raw materials and final food products. For wheat and wheat-based products, the EU maximum levels apply to deoxynivalenol (DON), zearalenone, aflatoxins, and ochratoxin A. This review provides a comprehensive overview on the different mycotoxins and their legal limits and on how processing of wheat can affect such contaminants, from raw material to highly processed final products, based on relevant scientific studies published in the literature. The potential compliance with EU maximum levels is discussed. Of the four mycotoxins regulated in wheat-based foods in the EU, most data are available for DON, whereas aflatoxins were rarely studied in the processing of wheat. Furthermore, available data on the effect of processing are outlined for mycotoxins not regulated by EU law-including modified and emerging mycotoxins-and which cover DON derivatives (DON-3-glucoside, mono-acetyl-DONs, norDONs, deepoxy-DON), nivalenol, T-2 and HT-2 toxins, enniatins, beauvericin, moniliformin, and fumonisins. The processing steps addressed in this review cover primary processing (premilling and milling operations) and secondary processing procedures (such as fermentation and thermal treatments). A special focus is on the production of baked goods, and processing factors for DON in wheat bread production were estimated. For wheat milling products derived from the endosperm and for white bread, compliance with legal requirements seems to be mostly achievable when applying good practices. In the case of wholemeal products, bran-enriched products, or high-cereal low-moisture bakery products, this appears to be challenging and improved technology and/or selection of high-quality raw materials would be required.

Fusarium toxins in corn food products: a survey of the Serbian retail market

This paper presents data on the occurrence of Fusarium toxins - zearalenone (ZEA), deoxynivalenol (DON) and fumonisins (FUMs) B1 and B2 - in corn flours and corn flakes marketed in Serbia. A total of 71 samples were collected over 2013-2016 and analysed using HPLC with UV or fluorescence detection. In the case of corn flours, none of the samples taken in 2013 exhibited the presence of ZEA or DON, whereas 90% were positive for FUMs. In 2015, occurrence was very high: ZEA 93%, DON 86% and FUMs 100% (mean 43.3, 322.6 and 323.0 μg kg^-1, respectively), with 21% of the samples exceeding the maximum level for ZEA and 7% for DON and FUMs. In 2016, a lower occurrence was recorded in the case of ZEA (75%) and DON (38%), with drastically lower mean contamination levels (six- and 10-fold, respectively), while FUMs stayed at 97%, with twofold lower mean. The maximum level was exceeded only for ZEA (3%). The frequency of ZEA-DON-FB1 co-occurrence was 86% in 2015 and 25% in 2016. Regarding corn flakes, occurrence summarised for the study period was 87% ZEA, 73% FUMs and 40% DON. One sample (7%) exceeded the maximum levels for both ZEA and DON. Observed occurrence changes were in agreement with the climatic conditions during corn growing seasons preceding the market release of the processed products.

The Status of Fusarium Mycotoxins in Sub-Saharan Africa: A Review of Emerging Trends and Post-Harvest Mitigation Strategies towards Food Control

Fusarium fungi are common plant pathogens causing several plant diseases. The presence of these molds in plants exposes crops to toxic secondary metabolites called Fusarium mycotoxins. The most studied Fusarium mycotoxins include fumonisins, zearalenone, and trichothecenes. Studies have highlighted the economic impact of mycotoxins produced by Fusarium. These arrays of toxins have been implicated as the causal agents of wide varieties of toxic health effects in humans and animals ranging from acute to chronic. Global surveillance of Fusarium mycotoxins has recorded significant progress in its control; however, little attention has been paid to Fusarium mycotoxins in sub-Saharan Africa, thus translating to limited occurrence data. In addition, legislative regulation is virtually non-existent. The emergence of modified Fusarium mycotoxins, which may contribute to additional toxic effects, worsens an already precarious situation. This review highlights the status of Fusarium mycotoxins in sub-Saharan Africa, the possible food processing mitigation strategies, as well as future perspectives.

Mycotoxin Contamination in the EU Feed Supply Chain: A Focus on Cereal Byproducts

Mycotoxins represent a risk to the feed supply chain with an impact on economies and international trade. A high percentage of feed samples have been reported to be contaminated with more than one mycotoxin. In most cases, the concentrations were low enough to ensure compliance with the European Union (EU) guidance values or maximum admitted levels. However, mycotoxin co-contamination might still exert adverse effects on animals due to additive/synergistic interactions. Studies on the fate of mycotoxins during cereal processing, such as milling, production of ethanol fuels, and beer brewing, have shown that mycotoxins are concentrated into fractions that are commonly used as animal feed. Published data show a high variability in mycotoxin repartitioning, mainly due to the type of mycotoxins, the level and extent of fungal contamination, and a failure to understand the complexity of food processing technologies. Precise knowledge of mycotoxin repartitioning during technological processes is critical and may provide a sound technical basis for feed managers to conform to legislation requirements and reduce the risk of severe adverse market and trade repercussions. Regular, economical and straightforward feed testing is critical to reach a quick and accurate diagnosis of feed quality. The use of rapid methods represents a future challenge.

Use of the electronic nose as a screening tool for the recognition of durum wheat naturally contaminated by deoxynivalenol: a preliminary approach

Fungal contamination and the presence of related toxins is a widespread problem. Mycotoxin contamination has prompted many countries to establish appropriate tolerance levels. For instance, with the Commission Regulation (EC) N. 1881/2006, the European Commission fixed the limits for the main mycotoxins (and other contaminants) in food. Although valid analytical methods are being developed for regulatory purposes, a need exists for alternative screening methods that can detect mould and mycotoxin contamination of cereal grains with high sample throughput. In this study, a commercial electronic nose (EN) equipped with metal-oxide-semiconductor (MOS) sensors was used in combination with a trap and the thermal desorption technique, with the adoption of Tenax TA as an adsorbent material to discriminate between durum wheat whole-grain samples naturally contaminated with deoxynivalenol (DON) and non-contaminated samples. Each wheat sample was analysed with the EN at four different desorption temperatures (i.e., 180 °C, 200 °C, 220 °C, and 240 °C) and without a desorption pre-treatment. A 20-sample and a 122-sample dataset were processed by means of principal component analysis (PCA) and classified via classification and regression trees (CART). Results, validated with two different methods, showed that it was possible to classify wheat samples into three clusters based on the DON content proposed by the European legislation: (a) non-contaminated; (b) contaminated below the limit (DON < 1,750 μg/kg); (c) contaminated above the limit (DON > 1,750 μg/kg), with a classification error rate in prediction of 0% (for the 20-sample dataset) and 3.28% (for the 122-sample dataset).

Fusarium mycotoxins in the food chain: maize-based snack foods

The fate of deoxynivalenol (DON), zearalenone (ZEA) and fumonisins B1 (FB1) and B2 (FB2) were examined in three representative snack food production methods. Assessing results on an 'as is' basis so as to compare results with EC legislation showed DON to be the most stable mycotoxin during the manufacture with mean levels in each finished products >68% of the levels in the starting ingredients. The concentrations of ZEA in the snack food ingredients during this study were very low but did allow limited studies that showed a mean 52% reduction during the manufacture of one snack product, but little reduction when producing a tortilla chip. In contrast, fumonisins were mostly lost (>90%) in two out of the three processes. However in a tortilla chip prepared from maize flour by extrusion, heating and frying, the amount of FB1 + FB2 remaining in the retail product was reduced on average by 59% which is similar to the 60% difference in the statutory levels for flour (products <500 micron) or 50% difference for grits (products >500 micron) and retail snack products. Thus the use of maize containing fumonisins in maize flour at levels just meeting legal limits would present some risk that a proportion of retail products might fail to meet legislation when the run to run variability is considered. The buyer/processor should thus avoid ingredients containing mycotoxin levels close to legislatory limits for use in processes where reduction at successive stages in manufacture are close to or less than those in the legislation. It is suggested that this study provides a useful indication of these. In commercial operation, there is a reluctance to specify raw materials at anything but the finishing product levels with implications for availability and cost.

HT-2 toxin and T-2 toxin in commercial cereal processing in the United Kingdom, 2004-2007

Legislation for mycotoxins in the European Union is being considered for T-2 toxin (T-2) and HT-2 toxin (HT-2). A four-year study on the fate of Fusarium mycotoxins in commercial milling and processing of cereals examined the incidence and concentrations of T-2 and HT-2 in wheat, oats and maize at intake to United Kingdom mills and during subsequent processing. Levels in wheat and maize were low and were not found in maize from Argentina although they did occur in some French consignments of maize. However, every sample of oats was contaminated with levels >20 µg/kg up to 1,600 and >3,000 µg/kg of T-2 and HT-2 respectively, the highest being found in consignments from the United Kingdom and Ireland while levels from Scandinavia were usually lower. Because of the low incidence and concentrations little information could be obtained on their fate during milling and food processing although their distribution in milling streams of wheat and maize was similar to that for other mycotoxins. In oats, most of the mycotoxins were found in the hulls after their removal from the groats so that levels in oats flakes produced from the groats never exceeded 65 and 55 µg/kg respectively. De-hulling of oats thus resulted in a co-product in which mycotoxins were concentrated, >100 µg/kg each of T-2 and HT-2. Two samples analysed for T-2 and 15 for HT-2 contained residues >1000 µg/kg, with maxima of 6,100 and 24,000 µg/kg respectively. Removal of discoloured oat groats by colour sorting reduced mycotoxin levels in the oat flake end product. Manufacture of batches of retail products from wheat and maize resulted in one snack product in which HT-2 at 12 µg/kg was detected. T-2 and HT-2 were undetected in other products. HT-2 was detected in 2 samples of the aqueous liquid drained from cookers during breakfast cereal manufacture.