Effect of the bread-making process on zearalenone levels

The effects of the bread-making process including fermentation with Saccharomyces cerevisiae and lactic acid bacteria (Lactobacillus casei, Lactobacillus rhamnosus, Lactobacillus acidophilus and Lactobacillus fermentum) and baking at 200°C on zearalenone (ZEA) levels were investigated. Standard solutions of ZEA were added to flour and then loaves of bread were prepared. Sourdough and three types of yeast including active dry yeast, instant dry yeast and compressed yeast were used for the fermentation of dough. ZEA levels in flour, dough and bread were determined by HPLC with fluorescence detection after extraction and clean-up on an immunoaffinity column. The highest reduction in levels of ZEA was found in the first fermentation (first proof), while the lowest reduction was observed in the baking stage. In addition, the results showed that compressed yeast had the maximum reduction potential on ZEA levels even at the baking stage.

Effects of processing on mycotoxin stability in cereals

The mycotoxins that generally occur in cereals and other products are not completely destroyed during food-processing operations and can contaminate finished processed foods. The mycotoxins most usually associated with cereal grains are aflatoxins, ochratoxins, deoxynivalenol, zearalenone and fumonisins. The various food processes that may have effects on mycotoxins include cleaning, milling, brewing, cooking, baking, frying, roasting, flaking, alkaline cooking, nixtamalization, and extrusion. Most of the food processes have variable effects on mycotoxins, with those that utilize high temperatures having the greatest effects. In general, the processes reduce mycotoxin concentrations significantly, but do not eliminate them completely. This review focuses on the effects of various thermal treatments on mycotoxins.

Zearalenone induced toxicity in SHSY-5Y cells: The role of oxidative stress evidenced by N-acetyl cysteine

Zearalenone (ZEN) is a mycotoxin from Fusarium species commonly found in many food commodities and are known to cause reproductive disorders, genotoxic and immunosuppressive effects. Although many studies have demonstrated the cytotoxic effects of ZEN, the mechanisms by which ZEN mediates its cytotoxic effects appear to differ according to cell type and route of exposure. Meantime, the available information on the neurotoxic effects of ZEN is very much limited. In the present study we evaluated the role of oxidative stress in ZEN mediated neurotoxicity in SH-SY5Y cells and investigated the possible underlying mechanism. ZEN induced ROS formation and elevated levels of MDA, loss of mitochondrial membrane potential (MMP) and increase in DNA damage in a dose dependent manner as assessed by COMET assay and agarose gel electrophoresis. However, there was no DNA damage by plasmid breakage assay at 6, 12 and 24h time points. DAPI staining showed apoptotic nuclei at 12 and 24h. Further, ZEN treated SH-SY5Y cells showed a marked suppressive effect on the neuronal gene expression. Use of an antioxidant N-acetylcysteine (NAC) reversed the toxin-induced generation of ROS and also attenuated loss of MMP. Collectively, these results suggest that ROS is the main upstream signal leading to increased ZEN mediated neurotoxicity in SH-SY5Y cells.

Preparation of 13C-labelled cis-zearalenone and its application as internal standard in stable isotope dilution analysis

Pure U-[13C18]-labelled cis-zearalenone (cis-ZEA) has been prepared and characterised as internal standard (ISTD) for a reliable quantification of cis-ZEA in contaminated food and feed products. The cis-isomer of the naturally trans-configurated Fusarium mycotoxin zearalenone is often neglected. However, isomerisation easily occurs by exposure of ZEA to (UV-)light. Thus, the applicability of the new cis-ZEA ISTD was demonstrated in a long-term isomerisation study comparing naturally trans-ZEA-contaminated edible oil with spiked edible oil. To estimate the benefits of the newly prepared cis-ZEA ISTD, various approaches to quantify cis-ZEA by high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) were compared. As a result, a significant bias was revealed if no appropriate cis-ZEA standards are used. Furthermore, the new ISTD was applied to the analysis of 15 edible oils by stable isotope dilution analysis in combination with HPLC-electrospray ionisation-MS/MS. One of the maize germ oils showed the presence of cis-ZEA above LOD (≯0.3 μg/kg), whereas two out of 15 maize germ oils were found to be contaminated with trans-ZEA (range 17.0-31.0 μg/kg).

A survey of trichothecenes, zearalenone and patulin in milled grain-based products using GC-MS/MS

An analytical protocol based on QuEChERS and gas chromatography-tandem mass spectrometry (GC-MS/MS) was successfully applied for the determination of trichothecenes, patulin and zearalenone in 182 milled grain-based samples. The analytical method was validated following the SANCO 1495/2011 document. LOQs were lower than 10μgkg(-1) for the selected mycotoxins. Recoveries of fortified cereals ranged between 76-108% and 77-114% at 20 and 80μgkg(-1), respectively, with relative standard deviation lower than 9%. More than 60% of the samples analysed showed deoxynivalenol contamination, followed by HT-2 toxin and nivalenol with frequencies of 12.1% and 10.4%, respectively. Co-occurrence of mycotoxins was also present in major cereals. A risk characterisation was carried out based on probable daily intake (PDI) and tolerable daily intake (TDI). Despite PDI of the average consumers were below TDI, special attention should be paid in high consumers as well as other susceptible population.

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.

Human exposure to mycotoxins and their masked forms through cereal-based foods in Belgium

In the present study, a quantitative dietary exposure assessment of mycotoxins and their masked forms was conducted on a national representative sample of the Belgian population using the contamination data of cereal-based foods. Cereal-based food products (n=174) were analysed for the occurrence of deoxynivalenol, 3-acetyldeoxynivalenol, 15-acetyldeoxynivalenol, zearalenone, α-zearalenol, β-zearalenol, T-2-toxin, HT-2-toxin, and their respective masked forms, including, deoxynivalenol-3-glucoside, zearalenone-4-glucoside, α-zearalenol-4-glucoside, β-zearalenol-4-glucoside and zearalenone-4-sulfate. Fibre-enriched bread, bran-enriched bread, breakfast cereals, popcorn and oatmeal were collected in Belgian supermarkets according to a structured sampling plan and analysed during the period from April 2010 to October 2011. The habitual intake of these food groups was estimated from a national representative food intake survey. According to a probabilistic exposure analysis, the mean (and P95) mycotoxin intake for the sum of the deoxynivalenol-equivalents, zearalenone-equivalents, and the sum of HT-2-and T-2-toxin for all cereal-based foods was 0.1162 (0.4047, P95), 0.0447 (0.1568, P95) and 0.0258 (0.0924, P95) μg kg(-1)body weight day(-1), respectively. These values were below the tolerable daily intake (TDI) levels for deoxynivalenol, zearalenone and the sum of T-2 and HT-2 toxin (1.0, 0.25 and 0.1 μg kg(-1)body weight day(-1), respectively). The absolute level exceeding the TDI for all cereal-based foods was calculated, and recorded 0.85%, 2.75% and 4.11% of the Belgian population, respectively.

Genotoxicity and inactivation of catechol metabolites of the mycotoxin zearalenone

Zearalenone (ZEN) is a highly estrogenic mycotoxin produced by Fusarium species. The adverse effects of ZEN and its reductive metabolite α-zearalenol (α-ZEL) are often compared to those of 17β-estradiol (E2) and estrone (E1). These endogenous steroidal estrogens are associated with an increased risk for cancer, which may be mediated by two mechanisms, i.e. (1) hormonal activity and (2) genotoxic effects after cytochrome P450-catalyzed metabolic activation to catechols. Like E1 and E2, ZEN and α-ZEL exhibit marked estrogenicity and also undergo aromatic hydroxylation to catechol metabolites. The subsequent methylation of catechols by catechol-O-methyltransferase (COMT) is generally considered as a detoxifying pathway. Imbalances between the activation and inactivation reactions can lead to the formation of reactive semiquinones and quinones, which can alkylate DNA or produce reactive oxygen species by redox cycling. In the present study, the genotoxicity of the catechol metabolites of ZEN, α-ZEL, E1 and E2 was determined in a cell-free system by measuring 8-oxo-2'-deoxyguanosine using a LC-DAD-MS(2) method. Each of the individual catechols of ZEN, α-ZEL, E1 and E2 induced oxidative DNA damage in calf thymus DNA. The ranking order of the DNA damaging activity was 15-hydroxy-ZEN/α-ZEL ≈ 2/4-hydroxy-E1/E2 > 13-hydroxy-ZEN/α-ZEL. When hepatic microsomes from different species were incubated with ZEN, the rat had the highest activity for catechol formation, followed by human, mouse, pig and steer. The amount of catechol metabolites correlated directly with the amount of oxidative damage in calf thymus DNA. The ranking order for the rate of methylation by human hepatic COMT was 2-hydroxy-E1/E2 >> 4-hydroxy-E1/E2 >> 13/15-hydroxy-ZEN/α-ZEL. Thus, the catechol metabolites of the mycoestrogen ZEN and its reductive metabolite α-ZEL exhibit a DNA-damaging potential comparable to that of the catechol metabolites of E1 and E2, but are much poorer substrates for inactivation by human COMT.

Combination of LC-MS2 and GC-MS as a Tool to Differentiate Oxidative Metabolites of Zearalenone with Different Chemical Structures

Recent studies on the mammalian and fungal metabolism of the mycotoxin zearalenone (ZEN) have disclosed the formation of six regioisomers of monohydroxy-ZEN and its reductive metabolite zearalenol (ZEL). Hydroxylation occurs at the aromatic ring or at one of four positions of the aliphatic macrocycle. In addition, an aliphatic ZEN epoxide, its hydrolysis product, and other products were identified in fungal cultures. In this paper, we report the product ion spectra of the [M-H]− ions of 22 oxidative metabolites of ZEN and ZEL, obtained by LC-MS2 analysis using a linear ion trap mass spectrometer with negative electrospray ionization. The MS2 spectra exhibit qualitative and quantitative differences which allow a clear distinction of most metabolites. Moreover, GC-MS analysis of the trimethylsilylated metabolites yields electron impact mass spectra with numerous fragment ions which can be used as fingerprint to confirm the chemical structure derived by LC-MS2 analysis.

Developments in mycotoxin analysis: an update for 2010-2011

This review highlights developments in mycotoxin analysis and sampling over a period between mid-2010 and mid-2011. It covers the major mycotoxins: aflatoxins, Alternaria toxins, ergot alkaloids, fumonisins, ochratoxin, patulin, trichothecenes, and zearalenone. Analytical methods for mycotoxins continue to be developed and published. Despite much interest in immunochemical methods and in the rapid development of LC-MS methodology, more conventional methods, sometimes linked to novel clean-up protocols, have also been the subject of research publications over the above period. Occurrence of mycotoxins falls outside the main focus of this review; however, where relevant to analytical method development, this has been mentioned.

Tools for investigating workplace-related risks from mycotoxin exposure

There is growing recognition and interest in the role of mycotoxins as health hazards in the workplace. Examples will illustrate what we know about certain mycotoxins in some occupational settings and what we need to know to make further progress in assessing their impact on human health. A range of mycotoxins has been detected in different workplaces, e.g. in agricultural and food processing facilities, greenhouses, and the waste management sector. Their occurrence, mainly in dust from different raw materials or processed products, is indicative of a potential health hazard. However, assessing risks for workplace-related mycotoxin exposures remains a challenging task for several reasons, including uncertainties with regard to the transfer from contaminated material into air (inhalable mycotoxin concentrations) and/or the toxin fraction absorbed upon dermal contact or after respiratory intake. Human biomonitoring studies can considerably reduce these uncertainties, and serve to assess workplace-related exposures (in addition to dietary mycotoxin intake). These studies require not only sensitive methods for analysis of mycotoxins and/or their metabolites in blood or urine (biomarkers of exposure) in a cohort of workers, but also data on the levels/range of these biomarkers in non-occupationally exposed persons to account for exposures resulting from oral intake of mycotoxin-contaminated food (dietary 'background'). Biomonitoring methods were first developed for aflatoxin B1, then for ochratoxin A, and more recently for deoxynivalenol and for fumonisin B. But, there are no such methods for many other important mycotoxins. So far, only a small number of biomonitoring studies have addressed the question whether occupational mycotoxin exposures (by inhalation) add significantly to those from dietary exposure to mycotoxins, as observed in the general population. Therefore, a risk assessment is hampered by major uncertainties regarding the true impact of occupational mycotoxin exposures. Human biomonitoring (with biomarkers of exposure and/or effect) is considered a valuable instrument, and should be developed further for mycotoxins of relevance in the workplace.

Zearalenone risk in European wheat

Zearalenone is an oestrogenic mycotoxin produced by several Fusarium species which can infect cereals, in particular wheat and maize. The predominant species responsible for zearalenone production is Fusarium graminearum, which also produces the trichothecene mycotoxin, deoxynivalenol. The infection and subsequent mycotoxin production by Fusarium spp. is largely dependent on rainfall at flowering and before harvest. High concentrations of zearalenone in particular, appear to be produced during delayed wet harvests. There has been a recent and ongoing increase in F. graminearum incidence resulting in increased occurrence of deoxynivalenol and zearalenone across northern Europe, where delayed wet harvests are more common. Zearalenone contamination of grain is largely restricted to the outer layers of wheat grain and therefore is partitioned into the bran fraction during milling. This results in higher concentrations of zearalenone in high fibre cereal products. After the delayed wet harvest in the UK in 2008, 29% of wheat at harvest exceeded the European limit for unprocessed cereals of 100 µg/kg. This resulted in difficulties in sourcing bran which would allow production of high fibre breakfast cereals within zearalenone limits and the European Commission provided a temporary derogation for high fibre breakfast cereals of 100 µg/kg zearalenone until 31 October 2009. Rainfall data and zearalenone concentrations in UK wheat from the last ten years were used to predict the occurrence of high zearalenone in wheat (10% or more of unprocessed wheat greater than 100 µg/ kg zearalenone). High zearalenone was predicted to occur one year in five for northern Europe which matches the observed incidence for the UK within the last ten years. As a consequence, current legislative limits for zearalenone in cereals and cereal products could impact on the availability of high fibre cereal products one year in five.