NIR-HSI as a tool to predict deoxynivalenol and fumonisins in maize kernels: a step forward in preventing mycotoxin contamination

BACKGROUND

Maize is frequently contaminated with deoxynivalenol (DON) and fumonisins B1 (FB1 ) and B2 (FB2 ). In the European Union, these mycotoxins are regulated in maize and maize-derived products. To comply with these regulations, industries require a fast, economic, safe, non-destructive and environmentally friendly analysis method.

RESULTS

In the present study, near-infrared hyperspectral imaging (NIR-HSI) was used to develop regression and classification models for DON, FB1 and FB2 in maize kernels. The best regression models presented the following root mean square error of cross validation and ratio of performance to deviation values: 0.848 mg kg-1 and 2.344 (DON), 3.714 mg kg-1 and 2.018 (FB1 ) and 2.104 mg kg-1 and 2.301 (FB2 ). Regarding classification, European Union legal limits for DON and FB1  + FB2 were selected as thresholds to classify maize kernels as acceptable or not. The sensitivity and specificity were 0.778 and 1 for the best DON classification model and 0.607 and 0.938 for the best FB1  + FB2 classification model.

CONCLUSION

NIR-HSI can help reduce DON and fumonisins contamination in the maize food and feed chain. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Near infrared hyperspectral imaging as a sorting tool for deoxynivalenol reduction in wheat batches

The present study aimed to evaluate the feasibility of using near-infrared hyperspectral imaging (NIR-HSI) and chemometrics for classification of individual wheat kernels according to their deoxynivalenol (DON) level. In total, 600 wheat kernels from samples naturally contaminated over the maximum EU level were collected, and the DON content in each individual wheat kernel was analyzed by UHPLC. Linear discriminant analysis (LDA) was employed for building classification models of DON using the EU maximum level as cut off level, and they were tested on balanced and imbalanced test sets. The results showed that the models presented a balanced accuracy of 0.71, that would allow to obtain safe batches from contaminated batches once the unsafe kernels had been rejected, but often more than 30% of the batch would be rejected. The work confirmed that NIR-HSI could be a feasible method for monitoring DON in individual kernels and removing highly contaminated kernels prior to food chain entry.

Inbred Selection for Increased Resistance to Kernel Contamination with Fumonisins

In temperate world-wide regions, maize kernels are often infected with the fumonisin-producing fungus Fusarium verticillioides which poses food and feed threats to animals and humans. As maize breeding has been revealed as one of the main tools with which to reduce kernel contamination with fumonisins, a pedigree selection program for increased resistance to Fusarium ear rot (FER), a trait highly correlated with kernel fumonisin content, was initiated in 2014 with the aim of obtaining inbred lines (named EPFUM) with resistance to kernel contamination with fumonisins and adapted to our environmental conditions. The new released EPFUM inbreds, their parental inbreds, hybrids involving crosses of one or two EPFUM inbreds, as well as commercial hybrids were evaluated in the current study. The objectives were (i) to assess if inbreds released by that breeding program were significantly more resistant than their parental inbreds and (ii) to examine if hybrids derived from EPFUM inbreds could be competitive based on grain yield and resistance to FER and fumonisin contamination. Second-cycle inbreds obtained through this pedigree selection program did not significantly improve the levels of resistance to fumonisin contamination of their parental inbreds; however, most EPFUM hybrids showed significantly better resistance to FER and fumonisin contamination than commercial hybrids did. Although European flint materials seem to be the most promising reservoirs of alleles with favorable additive and/or dominance effects for resistance to kernel contamination with fumonisins, marketable new Reid × Lancaster hybrids have been detected as they combine high resistance and yields comparable to those exhibited by commercial hybrids. Moreover, the white kernel hybrid EPFUM-4 × EP116 exploits the genetic variability within the European flint germplasm and can be an alternative to dent hybrid cultivation because white flint grain can lead to higher market prices.

Quantification and classification of deoxynivalenol-contaminated oat samples by near-infrared hyperspectral imaging

Deoxynivalenol (DON) is the most occurring mycotoxin in oat and oat-based products. Near-infrared hyperspectral imaging (NIR-HSI) has been proposed as a promising methodology for analysing DON contamination in the food industry. The present study aims to apply NIR-HSI for DON detection in oat kernels and to quantify and classify naturally DON-contaminated oat samples. Unground and ground oat samples were scanned by NIR-HSI before their DON content was determined by HPLC. The data were pre-treated and analysed by PLS regression and four classification methods. The most efficient DON prediction model was for unground samples (R² = 0.75 and RMSEP = 403.18 μg/kg), using twelve characteristic wavelengths with a special interest in 1203 and 1388 nm. The random forest algorithm of unground samples according to the EU maximum limit for unprocessed oats (1750 μg/kg) achieved a classification accuracy of 77.8 %. These findings indicate that NIR-HSI is a promising tool for detecting DON in oats.

Occurrence and Dietary Exposure Assessment to Enniatin B through Consumption of Cereal-Based Products in Spain and the Catalonia Region

Enniatin B (ENNB) is a mycotoxin produced by moulds from the Fusarium genera and its toxic effects are still not fully elucidated, hence a safe reference exposure value has not been established yet. ENNB is the most prevalent emerging mycotoxin and is widely found in cereal-based products, nevertheless, there are no comprehensive exposure assessment studies. For that reason, the aim of this study was to characterise the occurrence of ENNB and estimate the exposure of the Spanish and Catalan populations. A total of 347 cereal-based products were collected in 2019 and were analysed using liquid chromatography-tandem mass spectrometry. Consumption data were obtained from the national food consumption surveys (ENALIA) and a regional survey conducted in Catalonia. The global exposure was estimated using deterministic and probabilistic methods. The results showed a high occurrence of close to 100% in all foodstuffs, with a range from 6 to 269 µg/kg, and a strong correlation with the levels of deoxynivalenol. Children aged one-nine years were the most exposed, showing mean estimates in the range 308-324 ng/kg bw/day and 95th percentiles 697-781 ng/kg bw/day. This study stresses the need for further toxicological data to establish reference doses and conclude formal risk assessment, accounting for the co-occurrence with deoxynivalenol.

Preliminary survey of the occurrence of mycotoxins in cereals and estimated exposure in a northwestern region of Mexico

Mycotoxins have several toxicological implications. In the present study, we evaluate the presence of aflatoxin B₁ (AFB₁), ochratoxin A (OTA), and fumonisin (FB₁) in paddy rice, polished rice, and maize from the fields and markets in Nayarit State (Mexico). The results indicated the presence of AFB₁ in 21.21% of paddy rice samples and 11.11% of market maize samples. OTA was present in only 3.03% (one sample) of paddy rice samples. FB₁ was detected in 87.50% and 88.88% of maize samples from field and market, respectively. The estimated human exposure was calculated for FB₁ using the probable daily intake (PDI), which suggested that FB₁ could contribute to the development of diseases through the consumption of contaminated maize. Positive samples indicated that some rice and maize samples were not suitable for human consumption. Further efforts are needed to continue monitoring mycotoxins and update national legislation on mycotoxins accordingly.

Relevant Fusarium Mycotoxins in Malt and Beer

Mycotoxins are secondary fungal metabolites of high concern in the food and feed industry. Their presence in many cereal-based products has been numerously reported. Beer is the most consumed alcoholic beverage worldwide, and Fusarium mycotoxins originating from the malted and unmalted cereals might reach the final product. This review aims to describe the possible Fusarium fungi that could infect the cereals used in beer production, the transfer of mycotoxins throughout malting and brewing as well as an insight into the incidence of mycotoxins in the craft beer segment of the industry. Studies show that germination is the malting step that can lead to a significant increase in the level of all Fusarium mycotoxins. The first step of mashing (45 °C) has been proved to possess the most significant impact in the transfer of hydrophilic toxins from the grist into the wort. However, during fermentation, a slight reduction of deoxynivalenol, and especially of zearalenone, is achieved. This review also highlights the limited research available on craft beer and the occurrence of mycotoxins in these products.

Biomarkers of Deoxynivalenol Toxicity in Chickens with Special Emphasis on Metabolic and Welfare Parameters

Deoxynivalenol (DON), a trichothecene mycotoxin produced by Fusarium species, is the most widespread mycotoxin in poultry feed worldwide. Long term-exposure from low to moderate DON concentrations can produce alteration in growth performance and impairment of the health status of birds. To evaluate the efficacy of mycotoxin-detoxifying agent alleviating the toxic effects of DON, the most relevant biomarkers of toxicity of DON in chickens should be firstly determined. The specific biomarker of exposure of DON in chickens is DON-3 sulphate found in different biological matrices (plasma and excreta). Regarding the nonspecific biomarkers called also biomarkers of effect, the most relevant ones are the impairment of the productive parameters, the intestinal morphology (reduction of villus height) and the enlargement of the gizzard. Moreover, the biomarkers of effect related to physiology (decrease of blood proteins, triglycerides, hemoglobin, erythrocytes, and lymphocytes and the increase of alanine transaminase (ALT)), immunity (response to common vaccines and release of some proinflammatory cytokines) and welfare status of the birds (such as the increase of Thiobarbituric acid reactive substances (TBARS) and the stress index), has been reported. This review highlights the available information regarding both types of biomarkers of DON toxicity in chickens.

Intrathecal Administration of an Anti-nociceptive Non-CpG Oligodeoxynucleotide Reduces Glial Activation and Central Sensitization

Inflammatory pain associates with spinal glial activation and central sensitization. Systemic administration of IMT504, a non-CpG oligodeoxynucleotide originally designed as an immunomodulator, exerts remarkable anti-allodynic effects in rats with complete Freund´s adjuvant (CFA)-induced hindpaw inflammation. However, the anti-nociceptive mechanisms of IMT504 remain unknown. Here we evaluated whether IMT504 blocks inflammatory pain-like behavior by modulation of spinal glia and central sensitization. The study was performed in Sprague Dawley rats with intraplantar CFA, and a single lumbosacral intrathecal (i.t.) administration of IMT504 or vehicle was chosen to address if changes in glial activation and spinal sensitization relate to the pain-like behavior reducing effects of the ODN. Naïve rats were also included. Von Frey and Randall-Selitto tests, respectively, exposed significant reductions in allodynia and mechanical hypersensitivity, lasting at least 24 h after i.t. IMT504. Analysis of electromyographic responses to electrical stimulation of C fibers showed progressive reductions in wind-up responses. Accordingly, IMT504 significantly downregulated spinal glial activation, as shown by reductions in the protein expression of glial fibrillary acidic protein, CD11b/c, Toll-like receptor 4 (TLR4) and the phosphorylated p65 subunit of NFκB, evaluated by immunohistochemistry and western blot. In vitro experiments using early post-natal cortical glial cultures provided further support to in vivo data and demonstrated IMT504 internalization into microglia and astrocytes. Altogether, our study provides new evidence on the central mechanisms of anti-nociception by IMT504 upon intrathecal application, and further supports its value as a novel anti-inflammatory ODN with actions upon glial cells and the TLR4/NFκB pathway. Intrathecal administration of the non-CpG ODN IMT504 fully blocks CFA-induced mechanical allodynia and hypersensitivity, in association with reduced spinal sensitization. Administration of the ODN also results in downregulated gliosis and reduced TLR4-NF-κB pathway activation. IMT504 uptake into astrocytes and microglia support the concept of direct modulation of CFA-induced glial activation.

Standardization of near infrared hyperspectral imaging for wheat single kernel sorting according to deoxynivalenol level

The spatial recognition feature of near infrared hyperspectral imaging (HSI-NIR) makes it potentially suitable for Fusarium and deoxynivalenol (DON) management in single kernels to break with heterogeneity of contamination in wheat batches to move towards individual kernel sorting and provide more quick, environmental-friendly and non-destructive analysis than wet-chemistry techniques. The aim of this study was to standardize HSI-NIR for individual kernel analysis of Fusarium damage and DON presence, to predict the level of contamination and classify grains according to the EU maximum limit (1250 µg/kg). Visual inspection on Fusarium infection symptoms and HPLC analysis for DON determination were used as reference methods. The kernels were scanned in both crease-up and crease-down position and for different image captures. The spectra were pretreated by Multiplicative Scatter Correction (MSC) and Standard Normal Variate (SNV), 1st and 2nd derivatives and normalisation, and they were evaluated also by removing spectral tails. The best fitted predictive model was on SNV pretreated data (R² 0.88 and RMSECV 4.8 mg/kg) in which 7 characteristic wavelengths were used. Linear Discriminant Analysis (LDA), Naïve Bayes and K-nearest Neighbours models classified with 100% of accuracy 1st derivative and SNV pretreated spectra according to symptomatology and with 98.9 and 98.4% of correctness 1st derivative and SNV spectra, respectively. The starting point results are encouraging for future investigations on HSI-NIR technique application to Fusarium and DON management in single wheat kernels to overcome their contamination heterogeneity.

Effects of Deoxynivalenol-Contaminated Diets on Productive, Morphological, and Physiological Indicators in Broiler Chickens

Simple Summary

The presence of mycotoxins in feed is a really significant problem worldwide; it leads to adverse effects on animals and great economic losses, especially in the monogastric industry. Deoxynivalenol (DON) is one of these mycotoxins that contaminates poultry feed and consequently has negative effects on this specie. Different concentrations of DON (5 and 15 mg/kg feed) were tested in broiler chickens. Results showed that high levels could adversely affect productive and welfare parameters; however, organ weights, morphological intestine indicators, and biochemical parameters were affected at low and high level of dietary DON. In general, even the low level of DON (5 mg/kg), which is the guidance level in complete poultry feed could affect the physiological status of birds.

Abstract

The present study with 1-day-old male broilers (Ross 308) was conducted to evaluate the effects of deoxynivalenol (DON) at different levels (5 and 15 mg/kg feed) on growth performance, relative weight of organs, morphology of the small intestine, serum biochemistry, and welfare parameters of broiler chickens. Forty-five broiler chicks were randomly divided into three different experimental groups with five replicates each: (1) control group received a non-contaminated diet, (2) contaminated diet with 5 mg DON/kg of feed, and (3) contaminated diet with 15 mg DON/kg of feed for 42 days. Results showed that feed artificially contaminated with DON at guidance level (5 mg/kg diet) did not affect growth performance parameters. However, 15 mg/kg reduced body weight gain and altered feed efficiency. DON at two assayed levels significantly increased the absolute and relative weight of thymus and the relative weight of gizzard and decreased the absolute and the relative weight of the colon. Compared to controls, both doses affected small intestine morphometry parameters. In terms of biochemical indicators, DON at 5 mg/kg reduced the creatine kinase level and at 15 mg/kg DON reduced the cholesterol level. Furthermore, DON at 15 mg/kg induced more fear in broilers compared to broilers fed the guidance level. It was concluded that even the guidance level of DON did not affect the chickens’ performance. However, its toxic effect occurred in some organs and biochemical parameters.

Near-infrared hyperspectral imaging for deoxynivalenol and ergosterol estimation in wheat samples

The present study aimed to evaluate the use of hyperspectral imaging (HSI)-NIR spectroscopy to assess the presence of DON and ergosterol in wheat samples through prediction and classification models. To achieve these objectives, a first set of bulk samples was scanned by HSI-NIR and divided into two subsamples, one that was analysed for ergosterol and another that was analysed for DON by HPLC. This method was repeated for a second larger set to build prediction and classification models. All the spectra were pretreated and statistically processed by PLS and LDA. The prediction models presented a RMSEP of 1.17 mg/kg and 501 µg/kg for ergosterol and DON, respectively. Classification achieved an encouraging accuracy of 85.4% for an independent validation set of samples. The results confirm that HSI-NIR may be a suitable technique for ergosterol quantification and DON classification of samples according to the EU legal limit for DON.

Tri-octahedral bentonites as potential technological feed additive for Fusarium mycotoxin reduction

In 2009 the EU Regulation 386/2009 established a new functional group of feed additives called "substances for reduction of the contamination of feed by mycotoxin". Later, di-octahedral bentonite (1 m558) was authorised, as an anti-aflatoxin additive, being the only additive of this group authorised to date. This work aims to demonstrate the effectiveness of other bentonites, such as tri-octahedral bentonites, versus Fusarium-mycotoxins, since very few adsorbents have proved their effectiveness in relation to this group of mycotoxins. For this purpose, 7 bentonites (six of them tri-octahedral) and 7 commercial adsorbents, added at 0.02% (w/v), were assayed in an in vitro adsorption experiment using two simulated gastro-intestinal (GI) juices (pH 1.3 and 6.8) versus zearalenone (ZEN: 0.1-5 mg/L), fumonisin B₁ (FB₁: 1-10 mg/L) and deoxynivalenol (DON: 2-10 mg/L). Mycotoxin adsorption data were fitted to Langmuir and Freundlich isotherms. In vitro adsorption experiments showed that ZEN and FB₁ (in the latter case only in acid medium) were partially adsorbed, while the adsorption of DON was negligible. Moreover, the increase of adsorbent dose (up to 0.20%, w/v) significantly improved the in vitro adsorption of ZEN and FB₁, reaching >90% of adsorption. The present work proposes the use of some tri-octahedral bentonites as feed additives for Fusarium-mycotoxin reduction.

Fusarium mycotoxins in total mixed rations for dairy cows

Mycotoxins produced by certain fungal species of the Fusarium genus are frequently found as contaminants in cereals and feedstuffs. Fumonisins (FBs), deoxynivalenol (DON) and zearalenone (ZEN) are of special concern relative to animal health and productivity. The aim of this work was to analyse the levels of Fusarium mycotoxin contamination in samples of total mixed rations (TMRs) for dairy cows. To accomplish this analysis, an HPLC-MS/MS multi-mycotoxin method was developed and validated. The relation between the formulation of TMR samples and the presence of mycotoxins was also studied. From February 2016 to January 2018, a total of 193 TMR samples for dairy cows collected from farms located in different areas of Spain were analysed for the presence of FBs, ZEN, DON and their metabolites. In total, 112 samples (58%) were contaminated with at least one mycotoxin, and 38 samples (20%) presented more than one mycotoxin. FBs were the mycotoxins most frequently found (34% positive samples). DON was detected in 17% of samples, and ZEN was detected in 16% of samples. Among the metabolites analysed, only deoxynivalenol-3-glucoside (DON-3-Glc) and 15-acetyldeoxynivalenol (15-ADON) were detected. The levels of all the Fusarium mycotoxins studied were always below the values recommended by the European Commission for feedstuffs. The wide variety of ingredients used in the formulation of the analysed samples made it difficult to reach definite conclusions, although it seemed that some cereal silages and concentrates such as cereals or compound feed used as ingredients of the TMR may be related to the presence of mycotoxins.

Mycotoxins occurrence and fungal populations in different types of silages for dairy cows in Spain

Silages constitute a major component of the feed ration for dairy cows, being a potential source of mycotoxins due to the possible contamination by filamentous fungi capable of producing these toxic compounds. In this study, samples of different kinds of silages collected from farms located in four regions of Spain, were analysed to evaluate the occurrence of aflatoxins (AFs) and Fusarium mycotoxins. Lactic acid bacteria and fungal populations as well as pH and water activity were also studied. Penicillium, Geotrichum and Monascus were the main fungi identified in all the silages examined. The incidence of AFs was low (10 % of positive samples). Fusarium mycotoxins were detected in 40 % of the samples and fumonisins (FBs) were the most commonly detected. Maize silage was the most heavily contaminated type of silage. Levels of mycotoxins detected in positive samples did not exceed the EU guidance values. The lack of relationship between Fusarium counts and its mycotoxin concentrations suggested that mycotoxin production possibly occurred pre-ensiling or immediately post-ensiling. Outcomes showed that mould growth and mycotoxin contamination in silages should be regularly monitored in order to minimize the exposure of dairy cows to contaminated feed.

The fate of Fusarium mycotoxins (deoxynivalenol and zearalenone) through wort fermenting by Saccharomyces yeasts (S. cerevisiae and S. pastorianus)

The aim of this study was to evaluate the effect of 15 commercial yeasts in the mitigation of the Fusarium mycotoxins deoxynivalenol (DON) and zearalenone (ZEN) during the brewing process. Saccharomyces strains (10 strains of S. cerevisiae and 5 of S. pastorianus) were used to ferment DON and ZEN contaminated wort. Wort samples were taken every 24 h during fermentation, while mycotoxin analysis in yeast was performed at the end of fermentation (96 h); additionally, pH and ethanol content were measured daily. For mycotoxin analysis, after immunoaffinity purification of sample extracts, analysis was performed using an Ultra-High-Pressure Liquid Chromatograph coupled with a diode array or fluorescence detector (UHPLC-DAD/FLD). Mycotoxin presence had no significant effect on the ethanol production during brewing. At the end of fermentation, 10-17% of DON and 30-70% of ZEN had been removed, 6% of the initial concentration of DON and 31% of the ZEN being adsorbed by the yeast. Beermakers must pay careful attention to the raw material since a high percentage of DON could be present at the end of the beer fermentation process. Future studies should focus on the quantification of "masked" mycotoxins that are relevant to food security.

Usefulness of the analytical control of aflatoxins in feedstuffs for dairy cows for the prevention of aflatoxin M1 in milk

Aflatoxin M₁ (AFM₁) is a hydroxylated metabolite of aflatoxin B₁ (AFB₁) and can be excreted in milk of cows after consuming aflatoxin (AF)-contaminated feed. The aim of this research was to assess the levels of total AFs in samples of feedingstuff for dairy cows (n = 193) and the levels of AFM₁ in raw bulk tank milk samples (n = 375), in order to estimate the ratio of "AFB₁ feed input" versus "AFM₁ milk output" in four specific regions of Spain. Moreover, the correlation between the raw materials used as ingredients of the total mixed ration (TMR) and the presence of AFs was studied. About one-third (34.7%) of the feed samples were positive for total AFs in a range of 0.05-6.45 μg/kg, and 12.4% were positive for AFB₁. AFM₁ was detected in 18.9% of bulk milk samples, with concentrations ranging from 0.009 to 1.36 μg/kg. While none of the feed samples exceeded the European Union (EU) maximum content for AFB₁ in feedingstuff for dairy animals of 5 μg/kg, three bulk milk samples exceeded the EU maximum level for AFM₁ in milk of 50 ng/kg. The transfer ratio AFB₁/AFM₁, which was derived from AFB₁ levels in feed, AFM₁ levels in bulk tank milk, feed intake, and milk yield data, was 0.6-6%, which corresponded well with the range of published carry-over data for aflatoxins. Statistical analyses showed that the main sources of AFB₁ in TMR were maize silage, bagasse, soya bean husk, maize, alfalfa hay, cotton seed and compound feed, thus special attention should be paid in controlling these raw materials when used in TMR preparation. Although the analysis of AFs in feed did not correlate with the presence of AFM₁ in milk, monitoring feedstuffs is a useful tool in order to try and minimise AF-contamination of milk.

Frequency and levels of mycotoxins in beer from the Mexican market and exposure estimate for deoxynivalenol mycotoxins

The aim of the present study was to evaluate the occurrence of 23 mycotoxins in beer purchased in Mexico and to assess two exposure scenarios in the Mexican population through beer consumption. Multi-mycotoxin analysis of a total of 61 different beers (132 samples) was carried out using UHPLC-MS/MS equipment. Probability density functions were used to describe mycotoxins contamination. The daily intake of mycotoxins was estimated using a semi-probabilistic approach, applying the Monte Carlo method. Deoxynivalenol (DON) and its metabolites (deoxynivalenol-3-glucoside (DON3G) and 3-acetyl-deoxynivalenol (3ADON)) were the mycotoxins found in higher proportions in contaminated samples. None of the other mycotoxins overpassed the limit of quantification (LOQ) of the method. The combined intake of DON and its analogues ranged from 5.24 to 86.59 ng kg^-1 bw day^-1, which represent from 1.20 to 19.83% of the DON TDI. The results suggest that depending on the individual consumption of beer and depending on the type of beer, the intake of DON via beer could represent a significant percentage of the tolerable daily intake (TDI).

Probability models for growth and aflatoxin B1 production as affected by intraspecies variability in Aspergillus flavus

The probability of growth and aflatoxin B₁ (AFB₁) production of 20 isolates of Aspergillus flavus were studied using a full factorial design with eight water activity levels (0.84-0.98 a_w) and six temperature levels (15-40 °C). Binary data obtained from growth studies were modelled using linear logistic regression analysis as a function of temperature, water activity and time for each isolate. In parallel, AFB₁ was extracted at different times from newly formed colonies (up to 20 mm in diameter). Although a total of 950 AFB₁ values over time for all conditions studied were recorded, they were not considered to be enough to build probability models over time, and therefore, only models at 30 days were built. The confidence intervals of the regression coefficients of the probability of growth models showed some differences among the 20 growth models. Further, to assess the growth/no growth and AFB₁/no- AFB₁ production boundaries, 0.05 and 0.5 probabilities were plotted at 30 days for all of the isolates. The boundaries for growth and AFB₁ showed that, in general, the conditions for growth were wider than those for AFB₁ production. The probability of growth and AFB₁ production seemed to be less variable among isolates than AFB₁ accumulation. Apart from the AFB₁ production probability models, using growth probability models for AFB₁ probability predictions could be, although conservative, a suitable alternative. Predictive mycology should include a number of isolates to generate data to build predictive models and take into account the genetic diversity of the species and thus make predictions as similar as possible to real fungal food contamination.

Mycotoxins and beer. Impact of beer production process on mycotoxin contamination. A review

Beer is the most consumed alcoholic beverage in the world. Its contamination with mycotoxins is of public health concern, especially for heavy drinkers. Beer production implies a variety of operations which might impact the initial level of mycotoxins in a positive or negative way. The complexity of these operations do not give to the brewer a complete control on chemical and biochemical reactions that take place in the batch, but the knowledge about mycotoxin properties can help in identifying the operations decreasing their level in foodstuffs and in the development of mitigation strategies. This review discusses available data about mycotoxin evolution during malting and brewing process. The operations that may lead to a decrease in mycotoxin load are found to be steeping, kilning, roasting, fermentation and stabilization operations applied over the process (e.g. clarification). Also, other general decontamination strategies usually employed in food industry, such as hot water treatment of barley, ozonation or even the use of lactic acid bacteria starter cultures during malting or fermentation are considered.

UPLC-MS/MS analysis of ochratoxin A metabolites produced by Caco-2 and HepG2 cells in a co-culture system

Ochatoxin A (OTA) is one of the most important mycotoxins based on its toxicity. The oral route is the main gateway of entry of OTA into the human body, and specialized epithelial cells constitute the first barrier. The present study investigated the in vitro cytotoxic effect of OTA (5, 15 and 45 μM) and production of OTA metabolities in Caco-2 and HepG2 cells using a co-culture Transwell System to mimic the passage through the intestinal epithelium and hepatic metabolism. The results derived from MTS cell viability assays and transepithelial electrical resistance measurements showed that OTA was slightly cytotoxic at the lowest concentration at 3 h, but significant toxicity was observed at all concentrations at 24 h. OTA metabolites generated in this co-culture were ochratoxin B (OTB), OTA methyl ester, OTA ethyl ester and the OTA glutathione conjugate (OTA-GSH). OTA methyl ester was the major metabolite found in both Caco-2 and HepG2 cells after all treatments. Our results showed that OTA can cause cell damage through several mechanisms and that the OTA exposure time is more important that the dosage in in vitro studies. OTA methyl ester is proposed as an OTA exposure biomarker, although future studies should be conducted.

Effect of xylanase and α-amylase on DON and its conjugates during the breadmaking process

Deoxynivalenol (DON) is one of the most frequently occurring mycotoxins in wheat crops worldwide and poses a risk to human and animal health due to its wide range of adverse effects. Deoxynivalenol-3-glucoside (DON-3-glucoside) is a DON plant conjugate that is widely found in cereal products. As DON accumulation in the field seems unavoidable, it is important to investigate all of the conditions that affect its stability during food processing. One of the most consumed cereal product around the world is bread, however the published information about DON stability in bread shows a large variability of results because a huge amount of factors affect DON and its modified forms. So, the aim of this research was to study the fate of DON and its modified forms through the breadmaking process with the addition of xylanase and α-amylase at different fermentation temperatures. Moreover, different α-amylase and xylanase concentrations were added to the dough to be fermented. To quantify DON and its derived forms in the samples, liquid chromatography with double mass spectrophotometer was used. DON was reduced during fermentation and baking; however, the reduction at each step was related to the fermentation temperature. The presence of α-amylase and xylanase caused increases in DON during fermentation and during early baking. DON-3-glucoside was slightly reduced after fermentation and was widely increased (>80%) after baking. Deepoxy-deoxynivalenol (DOM-1) increased during the breadmaking process. Breadmaking process can reduce DON concentration, however xylanase and α-amylase presence cause increases of DON.

Single vs multiple-spore inoculum effect on growth kinetic parameters and modeled probabilities of growth and aflatoxin B1 production of Aspergillus flavus on pistachio extract agar

The objective of the present study was to assess the differences in modeled growth/AFB1 production probability and kinetic growth parameters for Aspergillus flavus inoculated as single spores or in a concentrated inoculation point (~500 spores). The experiment was carried out at 25°C and at two water activities (0.85 and 0.87) on pistachio extract agar (3%). Binary data obtained from growth and AFB1 studies were modeled using linear logistic regression analysis. The radial growth curve for each colony was fitted to a linear model for the estimation of the lag phase for growth and the mycelial growth rate. In general, radial growth rate and lag phase for growth were not normally distributed and both of them were affected by the inoculation type, with the lag phase for growth being more affected. Changing from the multiple spore to the single spore inoculation led to a delay of approximately 3-5days on the lag phase and higher growth rates for the multiple spore experiment were found. The same trend was observed on the probability models, with lower predicted probabilities when colonies came up from single spores, for both growth and AFB1 production probabilities. Comparing both types of models, it was concluded that a clear overestimation of the lag phase for growth occurred using the linear model, but only in the multiple spore experiment. Multiple spore inoculum gave very similar estimated time to reach some set probabilities (t10, t50 and t100) for growth or AFB1 production due to the abruptness of the logistic curve developed. The observed differences suggest that inoculum concentration greatly affects the outcome of the predictive models, the estimated times to growth/AFB1 production being much earlier for the concentrated inoculum than for a single spore colony (up to 9days). Thus the number of spores used to generate data in predictive mycology experiments should be carefully controlled in order to predict as accurately as possible the fungal behavior in a foodstuff.

Modelling the effect of pH and water activity in the growth of Aspergillus fumigatus isolated from corn silage

AIMS

The aim of this work was to use mathematical kinetic modelling to assess the combined effects of a_W, pH, O₂ availability and temperature on the growth rate and time to growth of Aspergillus fumigatus strains isolated from corn silage.

METHODS AND RESULTS

A full factorial design was used in which two factors were assayed: pH and a_W . The a_W levels assayed were 0·80, 0·85, 0·90, 0·92, 0·94, 0·96, 0·98 and 0·99. The levels of pH assayed were 3·5, 4, 4·5, 5, 6, 7, 7·5 and 8. The assay was performed at normal oxygen tension at 25 and 37°C, and at reduced oxygen tension at 25°C. Two strains of A. fumigatus isolated from corn silage were used. Kinetic models were built to predict growth of the strain under the assayed conditions. The cardinal models gave a good quality fit for radial growth rate data. The results indicate that the environmental conditions which take place during silage production, while limiting the growth of most micro-organisms, would not be able to control A. fumigatus. Moreover, pH levels in silage, far from limiting its growth, are also close to its optimum. Carbon dioxide at 5% in the environment did not significantly affect its growth.

CONCLUSIONS

A need for a further and controlled acidification of the silage exists, as no growth of A. fumigatus was observed at pH 3·5, as long as the organoleptic characteristics of the silage are not much compromised.

SIGNIFICANCE AND IMPACT OF THE STUDY

Aspergillus fumigatus is one of the major opportunistic pathogens able to cause illness such as allergic bronchopulmonary aspergillosis, aspergilloma and invasive aspergillosis to rural workers. Exposure of animals to A. fumigatus spores can result in infections, particularly in those organs exposed to external invasion, such as the airways, mammary gland and uterus at birth.

Time-course of germination, initiation of mycelium proliferation and probability of visible growth and detectable AFB1 production of an isolate of Aspergillus flavus on pistachio extract agar

The aim of this work was to assess the temporal relationship among quantified germination, mycelial growth and aflatoxin B₁ (AFB1) production from colonies coming from single spores, in order to find the best way to predict as accurately as possible the presence of AFB1 at the early stages of contamination. Germination, mycelial growth, probability of growth and probability of AFB1 production of an isolate of Aspergillus flavus were determined at 25 °C and two water activities (0.85 and 0.87) on 3% Pistachio Extract Agar (PEA). The percentage of germinated spores versus time was fitted to the modified Gompertz equation for the estimation of the germination parameters (geometrical germination time and germination rate). The radial growth curve for each colony was fitted to a linear model for the estimation of the apparent lag time for growth and the growth rate, and besides the time to visible growth was estimated. Binary data obtained from growth and AFB1 studies were modeled using logistic regression analysis. Both water activities led to a similar fungal growth and AFB1 production. In this study, given the suboptimal set conditions, it has been observed that germination is a stage far from the AFB1 production process. Once the probability of growth started to increase it took 6 days to produce AFB1, and when probability of growth was 100%, only a 40-57% probability of detection of AFB1 production was predicted. Moreover, colony sizes with a radius of 1-2 mm could be a helpful indicator of the possible AFB1 contamination in the commodity. Despite growth models may overestimate the presence of AFB1, their use would be a helpful tool for producers and manufacturers; from our data 5% probability of AFB1 production (initiation of production) would occur when a minimum of 60% probability of growth is observed. Legal restrictions are quite severe for these toxins, thus their control from the early stages of contamination throughout the food chain is of paramount importance.

Conidia survival of Aspergillus section Nigri, Flavi and Circumdati under UV-A and UV-B radiation with cycling temperature/light regime

BACKGROUND

Bio-geographical differences in fungal infection distribution have been observed around the world, confirming that climatic conditions are decisive in colonization. This research is focused on the impact of ultraviolet radiation (UV) on Aspergillus species, based on the consideration that an increase in UV-B radiation may have large ecological effects.

RESULTS

Conidia of six mycotoxigenic Aspergillus species isolated from vineyards located in the northeast and south of Spain were incubated for 15 days under light/dark cycles and temperatures between 20 and 30 °C per day. Additionally, 6 h of exposure to UV-A or UV-B radiation per day were included in the light exposure. UV irradiance used were 1.7 ± 0.2 mW cm(-2) of UV-A (peak 365 nm) and 0.10 ± 0.2 mW cm(-2) of UV-B (peak 312 nm). The intrinsic decrease in viability of conidia over time was accentuated when they were UV irradiated. UV-B radiation was more harmful.

CONCLUSION

Conidial sensitivity to UV light was marked in Aspergillus section Circumdati. Conidia pigmentation could be related to UV sensitivity. Different resistance was observed within species belonging to sections Flavi and Nigri. An increase in UV radiation could lead to a reduction in the Aspergillus spp. inoculum present in the field (vineyards, nuts, cereal crops). In addition, it could unbalance the spore species present in the field, leading to a higher predominance of dark-pigmented conidia.

Low doses of ochratoxin A induce micronucleus formation and delay DNA repair in human lymphocytes

The contamination of food commodities by fungal toxins has attracted great interest because many of these mycotoxins are responsible for different diseases, including cancer and other chronic illnesses. Ochratoxin A (OTA) is a mycotoxin naturally present in food, and long-term exposure to food contaminated with low levels of OTA has been associated with renal cancer. In the present study, the cytotoxicity, cytostaticity, and genotoxicity of OTA (0.075-15 µM) in human lymphocytes were evaluated. A comet assay, a modified comet assay (DNA repair assay), which uses N-hydroxyurea (NHU) to detect non-repaired lesions produced by OTA, and a cytokinesis-blocked micronucleus assay were used. Treatments with OTA were not cytotoxic, but OTA caused a cytostatic effect in human lymphocytes at a concentration of 15 µM. OTA (0.075-5 µM) produced a slight increase in the percentage of DNA in the comets and a delay in the DNA repair capacity of the lymphocytes. Micronucleus (MN) induction was observed at OTA concentrations of 1.5 and 5 µM. Our results indicate that OTA induces DNA stable damage at low doses that are neither cytotoxic nor cytostatic, and OTA delays the DNA repair kinetics. These findings indicate that OTA affects two pivotal events in the carcinogenesis pathway.

Targeting Fusarium graminearum control via polyamine enzyme inhibitors and polyamine analogs

Fusarium graminearum not only reduces yield and seed quality but also constitutes a risk to public or animal health owing to its ability to contaminate grains with mycotoxins. Resistance problems are emerging and control strategies based on new targets are needed. Polyamines have a key role in growth, development and differentiation. In this work, the possibility of using polyamine metabolism as a target to control F. graminearum has been assessed. It was found that putrescine induces mycotoxin production, correlating with an over expression of TRI5 and TRI6 genes. In addition, a homolog of the Saccharomyces cerevisiae TPO4 involved in putrescine excretion was up-regulated as putrescine concentration increased while DUR3 and SAM3 homologues, involved in putrescine uptake, were down-regulated. When 2.5 mM D, l-α-difluoromethylornithine (DFMO) was added to the medium, DON production decreased from 3.2 to 0.06 ng/mm(2) of colony and growth was lowered by up to 70 per cent. However, exogenous putrescine could overcome DFMO effects. Five polyamine transport inhibitors were also tested against F. graminearum. AMXT-1505 was able to completely inhibit in vitro growth and DON production. Additionally, AMXT-1505 blocked F. graminearum growth in inoculated wheat spikes reducing DON mycotoxin contamination from 76.87 μg/g to 0.62 μg/g.

Thermal stability and kinetics of degradation of deoxynivalenol, deoxynivalenol conjugates and ochratoxin A during baking of wheat bakery products

The stability of deoxynivalenol (DON), deoxynivalenol-3-glucoside (DON-3-glucoside), 3-acetyldeoxynivalenol (3-ADON), 15-acetyldeoxynivalenol (15-ADON), de-epoxy-deoxynivalenol (DOM-1) and ochratoxin A (OTA) during thermal processing has been studied. Baking temperature, time and initial mycotoxin concentration in the raw materials were assayed as factors. An improved UPLC-MS/MS method to detect DON, DON-3-glucoside, 3-ADON, 15-ADON and DOM-1 in wheat baked products was developed in the present assay. The results highlighted the importance of temperature and time in mycotoxin stability in heat treatments. OTA is more stable than DON in a baking treatment. Interestingly, the DON-3-glucoside concentrations increased (>300%) under mild baking conditions. On the other hand, it was rapidly reduced under harsh conditions. The 3-ADON decreased during the heat treatment; while DOM-1 increased after the heating process. Finally, the data followed first order kinetics for analysed mycotoxins and thermal constant rates (k) were calculated. This parameter can be a useful tool for prediction of mycotoxin levels.

Aflatoxins and ochratoxin A in pistachios sampled in Spain: occurrence and presence of mycotoxigenic fungi

A survey of the fungal contamination and occurrence of aflatoxins and ochratoxin A (OTA) in 50 pistachio nut samples collected from commercial stores around Catalonia (Spain) was carried out. Aspergillus flavus was found in 30% of samples, whereas Aspergillus section Nigri, Aspergillus ochraceus, and Penicillium verrucosum were found in 40%, 2% and 26% of samples, respectively. A total of 204 fungal isolates were obtained; 70.8% of A. flavus isolates were able to produce aflatoxin B1 and B2, whereas OTA production capacity was detected in 54.4% of the A. section Nigri biseriate isolates. Aflatoxins were detected in five samples (10% of total), all exceeding the maximum legal limit set for aflatoxin B1 (2 µg kg(-1)) or for total aflatoxins (4 µg kg(-1)), with one sample having a very high level of contamination (1134.5 µg kg(-1)). Only one sample of pistachio showed OTA contamination at 0.67 µg kg(-1). Simultaneous contamination by aflatoxins and OTA was not observed in these samples. It was concluded that the frequency of aflatoxins and OTA contamination in pistachio samples available in the Spanish market is relatively low. Thus, no significant contribution to health risk should be expected from aflatoxin consumption through pistachios among healthy consumers. However, the existence of single samples with an extremely high aflatoxin concentration reinforces the need for effective prevention strategies in pistachio processing and commercialization.

Effect of ultraviolet radiation A and B on growth and mycotoxin production by Aspergillus carbonarius and Aspergillus parasiticus in grape and pistachio media

The effects of two exposure times per day (6 and 16 h) of UV-A or UV-B radiation, combined with dark and dark plus light incubation periods during 7-21 d on fungal growth and mycotoxins production of Aspergillus species were studied. Aspergillus carbonarius and Aspergillus parasiticus were inoculated on grape and pistachio media under diurnal and nocturnal temperatures choosing light photoperiod according to harvest conditions of these crops in Spain. Ultraviolet irradiation had a significant effect on A. carbonarius and A. parasiticus colony size (diameter, biomass dry weight, and colony density) and mycotoxin accumulation, although intraspecies differences were observed. Inhibition of A. carbonarius fungal growth decreased when exposure time was reduced from 16 h to 6 h, but this was not always true for ochratoxin A (OTA) production. OTA reduction was higher under UV-A than UV-B radiation and the reduction increased along time conversely to the aflatoxins (AFs). Aflatoxin B1 (AFB1) was the main toxin produced by A. parasiticus except in the UV-B light irradiated colonies which showed a higher percentage of AFG than AFB. Morphological changes were observed in colonies grown under UV-B light.

Growth parameters of Penicillium expansum calculated from mixed inocula as an alternative to account for intraspecies variability

The aim of this work was to compare the radial growth rate (μ) and the lag time (λ) for growth of 25 isolates of Penicillium expansum at 1 and 20 ºC with those of the mixed inoculum of the 25 isolates. Moreover, the evolution of probability of growth through time was also compared for the single strains and mixed inoculum. Working with a mixed inoculum would require less work, time and consumables than if a range of single strains has to be used in order to represent a given species. Suitable predictive models developed for a given species should represent as much as possible the behavior of all strains belonging to this species. The results suggested, on one hand, that the predictions based on growth parameters calculated on the basis of mixed inocula may not accurately predict the behavior of all possible strains but may represent a percentage of them, and the median/mean values of μ and λ obtained by the 25 strains may be substituted by the value obtained with the mixed inoculum. Moreover, the predictions may be biased, in particular, the predictions of λ which may be underestimated (fail-safe). Moreover, the prediction of time for a given probability of growth through a mixed inoculum may not be accurate for all single inocula, but it may represent 92% and 60% of them at 20 and 1 ºC, respectively, and also their overall mean and median values. In conclusion, mixed inoculum could be a good alternative to estimate the mean or median values of high number of isolates, but not to account for those strains with marginal behavior. In particular, estimation of radial growth rate, and time for 0.10 and 0.50 probability of growth using a cocktail inoculum accounted for the estimates of most single isolates tested. For the particular case of probability models, this is an interesting result as for practical applications in the food industry the estimation of t10 or lower probability may be required.

The fate of deoxynivalenol and ochratoxin A during the breadmaking process, effects of sourdough use and bran content

Deoxynivalenol (DON) and ochratoxin A (OTA) are mycotoxins produced by fungal species which can contaminate, alone or simultaneously, cereal-based products such as bread. Due to the increasing interest in the beneficial effects of dietary bran, bran bread has attained high consumption. Usually, the higher mycotoxin concentrations in cereals are found in the external layers of the grain (bran), leading to higher concentration of DON and OTA in breads with added bran. Moreover, the use of sourdough in breadmaking is increasing, but no studies about its effect in the mycotoxins content exist. The objective of this study was to determine the variation of concentration of these mycotoxins during the breadmaking process including the following factors: two initial mycotoxin concentrations in the initial mix of ingredients, four different bran contents, and use of sourdough. OTA was confirmed to be quite stable during the breadmaking process, regardless of the assayed factors. DON concentration during breadmaking was not significantly affected by bran content of bread. However, it was significantly affected by kneading and fermentation steps in opposite way depending on sourdough use and flour contamination level: if DON reduction occurs during fermentation, this leads to a safer situation, but the possible increase in DON should be considered with care, as it can compensate the expected dilution effect by recipe. Finally, the results on deoxynivalenol-3-glucoside (DON-3-G), although preliminar, suggest an increase of this toxin during fermentation, but mainly during baking.

Critical environmental and genotypic factors for Fusarium verticillioides infection, fungal growth and fumonisin contamination in maize grown in northwestern Spain

In northwestern Spain, where weather is rainy and mild throughout the year, Fusarium verticillioides is the most prevalent fungus in kernels and a significant risk of fumonisin contamination has been exposed. In this study, detailed information about environmental and maize genotypic factors affecting F. verticillioides infection, fungal growth and fumonisin content in maize kernels was obtained in order to establish control points to reduce fumonisin contamination. Evaluations were conducted in a total of 36 environments and factorial regression analyses were performed to determine the contribution of each factor to variability among environments, genotypes, and genotype × environment interactions for F. verticillioides infection, fungal growth and fumonisin content. Flowering and kernel drying were the most critical periods throughout the growing season for F. verticillioides infection and fumonisin contamination. Around flowering, wetter and cooler conditions limited F. verticillioides infection and growth, and high temperatures increased fumonisin contents. During kernel drying, increased damaged kernels favored fungal growth, and higher ear damage by corn borers and hard rainfall favored fumonisin accumulation. Later planting dates and especially earlier harvest dates reduced the risk of fumonisin contamination, possibly due to reduced incidence of insects and accumulation of rainfall during the kernel drying period. The use of maize varieties resistant to Sitotroga cerealella, with good husk coverage and non-excessive pericarp thickness could also be useful to reduce fumonisin contamination of maize kernels.

Mycotoxins: occurrence, toxicology, and exposure assessment

Mycotoxins are abiotic hazards produced by certain fungi that can grow on a variety of crops. Consequently, their prevalence in plant raw materials may be relatively high. The concentration of mycotoxins in finished products is usually lower than in raw materials. In this review, occurrence and toxicology of the main mycotoxins are summarised. Furthermore, methodological approaches for exposure assessment are described. Existing exposure assessments, both through contamination and consumption data and biomarkers of exposure, for the main mycotoxins are also discussed.

Equisetum arvense hydro-alcoholic extract: phenolic composition and antifungal and antimycotoxigenic effect against Aspergillus flavus and Fusarium verticillioides in stored maize

BACKGROUND

Maize is a very important cereal for human and animal diet, but it can be contaminated by moulds and their mycotoxins. On the other hand, natural plant products with antimicrobial properties could possibly used to control mycotoxigenic fungi in foods and feeds. In this study, Equisetum arvense extract was tested for the efficacy on Aspergillus section Flavi and Fusarium section Liseola growth. Natural contaminated maize was used in this study and extract was added under different water activities (a(w)) - 0.90 and 0.95 - for Aspergillus section Flavi and Fusarium section Liseola, respectively. Moulds were inoculated in maize and incubated during 30 days.

RESULTS

We confirm that E. arvense extract may be effective for the inhibition of Aspergillus section Flavi in maize with high levels of this mould. Moreover, this extract showed a good inhibition of growth on Fusarium section Liseola levels. Aflatoxin and fumonisin production was not affected by the extract.

CONCLUSIONS

E. arvense extract could be an alternative to synthetic fungicides to control maize mycobiota level in moist grain.

Effect of food processing on exposure assessment studies with mycotoxins

The goals of the present work were, on the one hand, to assess the effect of baking on the stability of zearalenone (ZEA) and deoxynivalenol (DON), as well as the transfer of DON from pasta to boiling water, and, on the other hand, to quantify the impact of DON depletion, during cooking of pasta, on overall exposure estimates. Therefore, the bread-making process was simulated on a pilot-plant scale by using naturally contaminated flour with DON and ZEA. Transfer of DON from pasta to water was evaluated at different boiling times. Pasta was prepared on a pilot-plant scale by using naturally contaminated durum wheat flour; subsequently, it was boiled simulating home cooking. The experiments examined the stability of DON and ZEA during the bread-making process, including fermentation with Saccharomyces cerevisiae and baking at 200°C. Our results showed a high transfer of DON from pasta to boiling water, reaching depletion levels of almost 75%, which correlated with levels found in water. Accordingly, these cooking depletion rates were computed through a stochastic exposure model to weight their impact on the final exposure estimates. Finally, statistically significant differences were found in most of the parameters and populations assessed, but these were not enough to consider the process as protective because the contribution of pasta to the overall DON intake was commonly low.