Occurrence of deoxynivalenol and its 3-β-D-glucoside in wheat and maize

Deoxynivalenol-3-β-D-glucoside (D3G), a phase II plant metabolite of the mycotoxin deoxynivalenol (DON), occurs in naturally Fusarium-contaminated cereals. In order to investigate the frequency of occurrence as well as the relative and absolute concentrations of D3G in naturally infected cereals, 23 wheat samples originating from fields in Austria, Germany and Slovakia as well as 54 maize samples from Austrian fields were analysed for DON and D3G by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Both analytes were detected in all the 77 field samples. DON was found at levels from 42 to 4130 ng g^?1 (977 ± 1000 ng g^?1 on average). The D3G concentrations in all cereal samples were in the range 10–1070 ng g^?1 (216 ± 253 ng g^?1 on average), corresponding to about 5–46 mol% of their DON concentrations (15 ± 8 mol% on average).     

Is organically produced wheat a source of tocopherols and tocotrienols for health food?

Forty organically grown spring and winter wheat genotypes were investigated for content and compositions of tocopherol and tocotrienol. The selected genotypes belonged to five different genotypic groups, i.e. landraces, old cultivars, modern cultivars, spelt wheat, and primitive wheat. The total tocochromanols content (21.9–37.3 mg/kg) wheat were in similar ranges as previously reported for conventionally grown wheat. The vitamin E activity varied among the genotypic groups and corresponded to 12–25% of the recommended daily intake. Primitive wheat was found to contain the highest percentage of tocotrienols (74%). Content of tocochromanols and vitamin E activity are known to decrease by heating. Organic wheat is more commonly consumed as whole and sprouted grain when compared to conventional wheat and might therefore be a good source of tocochromanols in health food. The large variation in tocopherols and tocotrienols in the investigated wheat genotypes indicated a great potential for the development of specific wheat genotypes with health promoting properties in future breeding programmes.     

Stability of DON and DON-3-glucoside during baking as affected by the presence of food additives

The mycotoxin deoxynivalenol (DON) is one of the most common mycotoxins of cereals worldwide, and its occurrence has been widely reported in raw wheat. The free mycotoxin form is not the only route of exposure; modified forms can also be present in cereal products. Deoxynivalenol-3-glucoside (DON-3-glucoside) is a common DON plant conjugate. The mycotoxin concentration could be affected by food processing; here, we studied the stability of DON and DON-3-glucoside during baking of small doughs made from white wheat flour and other ingredients. A range of common food additives and ingredients were added to assess possible interference: ascorbic acid (E300), citric acid (E330), sorbic acid (E200), calcium propionate (E282), lecithin (E322), diacetyltartaric acid esters of fatty acid mono- and diglycerides (E472a), calcium phosphate (E341), disodium diphosphate (E450i), xanthan gum (E415), polydextrose (E1200), sorbitol (E420i), sodium bicarbonate (E500i), wheat gluten and malt flour. The DON content was reduced by 40%, and the DON-3-glucoside concentration increased by >100%, after baking for 20 min at 180°C. This confirmed that DON and DON-3-glucoside concentrations can vary during heating, and DON-3-glucoside could even increase after baking. However, DON and DON-3-glucoside are not affected significantly by the presence of the food additives tested.     

Comparison of glycemic index of spelt and wheat bread in human volunteers

The assessment of the glycemic index (GI) seems to be an important parameter to take into account in order to better understand the physiologic effects of foods with high carbohydrate levels. Among cereals, which are major sources of carbohydrates, spelt (Triticum spelta L.) has been considered as particularly interesting from a nutritional point of view. The aim of this study was to evaluate in vivo the GI of white spelt bread in healthy subjects. The wheat (Triticum aestivum L.) white bread was used as reference food. To avoid differences in the production of both breads, spelt and wheat breads were baked under the same controlled conditions. Results showed that the glycemic profile of spelt white bread was not different from that of wheat white bread (GI of 93 ± 9). The area under the glycemic curve significantly and negatively correlated to fasting glycemia and carbohydrate intake during evening meals preceding the test. In conclusion, the glycemic response to spelt bread was similar to that of wheat bread. However, in order to avoid more inter-individual variability, our data supports the importance to propose standardised carbohydrate content for the last meal before evaluating the GI of food.     

Survey of deoxynivalenol and its conjugates deoxynivalenol-3-glucoside and 3-acetyl-deoxynivalenol in 374 beer samples

Beer is one of the most popular beverages worldwide. Malted cereal grains are among the basic ingredients and hence mycotoxin contamination might occur. Previous studies reported the presence of the Fusarium mycotoxins deoxynivalenol (DON) and 3-acetyl-deoxynivalenol (3ADON), as well as of the masked mycotoxin deoxynivalenol-3-glucoside (D3G) in beer. In the present survey, 374?beer samples from 38?countries with a focus on Austrian (156) and German (64) beers were analysed for the presence of D3G, DON and 3ADON. Beers were assigned to the following six categories: pale (217), wheat (46), dark (47), bock (20), nonalcoholic beers (19) and shandies (25). In total, 348 and 289 beers (93 and 77%, respectively) contained D3G and DON at the levels above the limit of detection, whereas 3ADON was not detected in any of the samples. Average concentrations of all beers were 6.9?µg?L^?1 for D3G and 8.4?µg?L^?1 in the case of DON. Nonalcoholic beers and shandies showed the lowest contaminations, 1.5 and 3.2?µg?L^?1 for D3G and 2.7 and 4.4?µg?L^?1 for DON, respectively. In bock beers characterised by a higher gravity, a significant trichothecene load of 14.8?µg?L^?1 D3G and 12.4?µg?L^?1 DON was found. The highest contamination (81?µg?L^?1 D3G, 89?µg?L^?1 DON) was detected in a pale beer from Austria, underlining the importance of this study for food safety. The molar D3G to DON ratio ranged between 0.11 and 1.25 and was 0.56 on average. Concluding, the average contamination of beer is not of toxicological concern for moderate beer drinkers. However, in the case of heavy beer drinkers, beer consumption may considerably contribute to the overall intake of DON, which might even lead to exceeding the maximum tolerable limits established for this Fusarium toxin.     

Estimating deoxynivalenol contents of wheat samples containing different levels of Fusarium-damaged kernels by diffuse reflectance spectrometry and partial least square regression

Fusarium head blight is a fungal disease causing yield losses and mycotoxin contamination in wheat and other cereals. Wheat kernels (cultivar Ritmo) were sampled in 2001, 2002, 2003, and 2006 and Fusarium-damaged kernels were separated from sound grain based on visual assessment. Subsequently, grain lots containing 0, 20, 40, 60, 80, and 100% of damaged kernels were compiled. Each lot was split and the spectrometric reflectance (wavelengths 350-2500 nm) was measured using subgroup one, while the concentration of the mycotoxin deoxynivalenol (DON) was determined by high-performance liquid chromatography in subgroup two. DON concentrations in batches classified as sound were not significantly different from 0. Estimating DON contents from the percentage of Fusarium-damaged kernels was impeded by vast variability, resulting in a coefficient of determination of 0.49. Using spectrometric data subjected to partial least square regression allowed estimating DON contents with higher accuracy, in particular at elevated percentages of damaged kernels. The coefficient of determination was 0.84 for the relationship between DON contents estimated based on spectrometric data and the DON contents measured. The intercept of a regression line fitted through a plot of estimated versus measured DON contents was 0.89 ± 3.61 mg/kg. Since intercept + standard error was larger than the actual legal limit (1.25 mg DON per kg dry grain in the European Union), the spectrometric procedure was still not precise enough to allow a reliable separation of grain samples with DON contents below 1.25 mg/kg from samples with DON contents above the limit. However, spectrometric data also allowed estimating the DON content of the average damaged kernel within a given lot composed of sound and damaged kernels, which is probably the reason for the reduction of the fraction of unexplained variance by 35% compared to the visual approach and illustrates that spectrometric approaches can make a contribution to reducing DON contents of wheat grain.     

Analysis of deoxynivalenol and deoxynivalenol-3-glucosides content in Canadian spring wheat cultivars inoculated with Fusarium graminearum

Contamination of wheat grains with Fusarium mycotoxins and their modified forms is an important issue in wheat industry. The objective of this study was to analyse the deoxynivalenol (DON) and deoxynivalenol-3-glucosides (D3G) content in Canadian spring wheat cultivars grown in two locations, inoculated with a mixture of 3-acetyldeoxynivalenol (3-ADON)-producing Fusarium graminearum strains and a mixture of 15-acetlyldeoxynivalenol (15-ADON)-producing F. graminearum strains. According to the analysis of variance, significant differences were observed among the cultivars for Fusarium head blight (FHB) disease index, Fusarium-damaged kernel percentage (%FDK), DON content and D3G content. When the effect of chemotype was considered, significant differences were observed for FHB disease index, FDK percentage and DON content. The D3G content and D3G/DON ratio were not significantly different between the chemotypes, except for D3G content at the Winnipeg location. The Pearson correlation coefficient between DON and D3G was 0.84 and 0.77 at Winnipeg and Carman respectively. The highest D3G/DON ratio was observed in cultivars Carberry (44%) in Carman and CDC Kernen (63.8%) in Winnipeg. The susceptible cultivars showed lower D3G/DON ratio compared with the cultivars rated as moderately resistant and intermediate. The current study indicated that Canadian spring cultivars produce D3G upon Fusarium infection.     

Occurrence of mycotoxins in spelt and common wheat grain and their products

Organic farming does not allow the use of conventional mineral fertilizers and crop protection products. As a result, in our experiments we chose to grow different species of cereals and to see how cereal species affect mycotoxin accumulation. This study describes the occurrence of deoxynivalenol (DON), zearalenone (ZEA) and T-2/HT-2 toxin in a survey of spelt and common wheat and their bran as well as flour. The analysis was conducted using an enzyme-linked immunosorbent assay (ELISA) method. The concentrations of DON, ZEA and T-2/HT-2 in Triticum spelta and T. aestivum were influenced by species, cereal type and year interaction. The highest concentrations of these mycotoxins were found in spelt grain with glumes, in spelt glumes and in spring wheat. These results show significantly higher concentrations of Fusarium toxins in glumes than in dehulled grain, which indicates the possible protective effect of spelt wheat glumes. The lowest DON, ZEA and T-2/HT-2 concentrations were determined in spelt grain without glumes. The research shows that it is potentially risky to produce bran from grain in which mycotoxin concentrations are below limits by European Union Regulation No. 1881/2006, since the concentration of mycotoxins in bran can be several times higher than that in grain. As a result, although bran is a dietary product characterised by good digestive properties, it can become a harmful product that can cause unpredictable health damage.     

Effects of Fusarium infection on the amino acid composition of winter wheat grain

Winter wheat (susceptible cultivar Ritmo) was grown in 2006 near Kiel and in 2007 near Heide in northern Germany. Plants were inoculated at anthesis using a Fusarium graminearum macroconidial suspension. The percentage of Fusarium-damaged kernels (FDK) ranged from 0 ± 2% to 28 ± 2%. The contents of the Fusarium mycotoxin deoxynivalenol (DON) and wheat amino acids were determined in the grain. Levels of the amino acids alanine, lysine, and tyrosine increased with the percentage of FDK or DON contents whereas glutamic acid contents decreased. Aspartic acid and threonine were not related to the percentage of FDK or DON contents. Effects of Fusarium infection on other amino acids were significant only at the sampling site with the higher degree of Fusarium-damage. Interestingly, those amino acids that increased consistently and significantly with the degree of Fusarium-damage are derived from phosphoenolpyruvate or pyruvate, suggesting that pathogen-induced changes in the glycolytic input for amino acid biosynthesis play a significant role for the amino acid composition of Fusarium-damaged winter wheat grain. On average, amino acid contents decreased by 0.13% compared to the amino acid content of sound kernels upon an increase of 1% of FDK.     

A biomarker survey of urinary deoxynivalenol in China: the Shanghai Women's Health Study

Deoxynivalenol (DON) is a trichothecene mycotoxin found on wheat, maize and barley. In ecological surveys in China, DON and other trichothecenes have been implicated in acute poisoning episodes and linked with the incidence of esophageal cancer. In order to better understand exposure patterns, this pilot survey provided a combined measure of urinary un-metabolised or free DON (fD) and its glucuronide metabolite (DG) in a subset of 60 samples taken from the Shanghai Women's Health Study cohort, China. Samples were collected in 1997/1998 from women age 40–70 years. Urinary fD+DG combined was detected in 58/60 (96.7%) samples (mean 5.9?ng DON/mg creatinine; range nd – 30.5); a similar frequency, and a mean level approximately half, of that previously observed for women in the UK. Wheat consumption was approximately 25% of that consumed by western diets; thus DON contamination of wheat may be higher in Shanghai than the UK. The de-epoxy metabolite of DON, a detoxification product observed in animals, was not detected, suggesting that humans may be particularly sensitive to DON due to a more restricted detoxification capacity.     

Transfer of Fusarium mycotoxins and ‘masked’ deoxynivalenol (deoxynivalenol-3-glucoside) from field barley through malt to beer

The fate of five Fusarium toxins — deoxynivalenol (DON), sum of 15- and 3-acetyl-deoxynivalenol (ADONs), HT-2 toxin (HT-2) representing the main trichothecenes and zearalenone (ZON) during the malting and brewing processes — was investigated. In addition to these ‘free’ mycotoxins, the occurrence of deoxynivalenol-3-glucoside (DON-3-Glc) was monitored for the first time in a beer production chain (currently, only DON and ZON are regulated). Two batches of barley, naturally infected and artificially inoculated with Fusarium spp. during the time of flowering, were used as a raw material for processing experiments. A highly sensitive procedure employing high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was validated for the analysis of ‘free’ Fusarium mycotoxins and DON-conjugate in all types of matrices. The method was also able to detect nivalenol (NIV), fusarenon-X (FUS-X) and T-2 toxin (T-2); nevertheless, none of these toxins was found in any of the samples. While steeping of barley grains (the first step in the malting process) apparently reduced Fusarium mycotoxin levels to below their quantification limits (5–10 µg kg^?1), their successive accumulation occurred during germination. In malt, the content of monitored mycotoxins was higher compared with the original barley. The most significant increase was found for DON-3-Glc. During the brewing process, significant further increases in levels occurred. Concentrations of this ‘masked’ DON in final beers exceeded ‘free’ DON, while in malt grists this trichothecene was the most abundant, with the DON/DON-3-Glc ratio being approximately 5:1 in both sample series. When calculating mass balance, no significant changes were observed during brewing for ADONs. The content of DON and ZON slightly decreased by a maximum of 30%. Only traces of HT-2 were detected in some processing intermediates (wort after trub removal and green beer).     

Effect of ozone treatment on the safety and quality of malting barley

Molds and their mycotoxins are an expensive problem for the malting and brewing industries. Deoxynivalenol (DON) is a mycotoxin that is associated with Fusarium spp. These fungi frequently cause Fusarium head blight in wheat and barley in the midwestern region of the United States; Manitoba, Canada; Europe; and China. Barley growers and malt producers would benefit from a postharvest control method for mold growth and DON production. We evaluated the use of gaseous ozone (O(3)) for preventing Fusarium growth and mycotoxin production while maintaining malt quality characteristics. Micromalting was performed in three replications under standard conditions. Ozone treatment was applied to malting barley during steeping via a submerged gas sparger. Ozone treatment conditions were 26 mg/cm(3) for 120 min after 2 and 6 h of steeping. The effects of gaseous ozone on DON, aerobic plate counts, Fusarium infection, and mold and yeast counts of barley throughout the malting process were measured. Various quality parameters of the malt were measured after kilning. Statistical tools were used to determine the significance of all results. Ozonation of malting barley during steeping did not lead to significant reductions in aerobic plate counts but did lead to a 1.5-log reduction in mold and yeast counts in the final malt. The influence of gaseous ozone on DON concentration was inconclusive because of the low initial concentrations of DON in the barley. Ozone significantly reduced Fusarium infection in germinated barley. Gaseous ozone did not negatively influence any aspect of malt quality and may have subtle beneficial effects on diastatic power and β-glucan concentrations.     

Detection of a new Fusarium masked mycotoxin in wheat grain by high-resolution LC-Orbitrap™ MS

A new Fusarium mycotoxin glucoside, fusarenon X-glucoside (FUXGlc), is reported for the first time in wheat grain that was artificially infected with Fusarium fungi. This new glucoside was identified using LC Orbitrap high-resolution mass spectrometry (LC-Orbitrap MS) analysis on the basis of accurate mass measurement of characteristic ions and MS/MS fragmentation patterns. Although the absolute structure of FUXGlc was not clarified by LC-MS, 3-OH glucosylation seems to be the most probable structure based on the fragment profile and considering that deoxynivalenol-3-glucoside (DON3Glc) was reported as the predominant glucosylated derivative of the structurally similar mycotoxin, deoxynivalenol (DON). Another mycotoxin glucoside, nivalenol-glucoside (NIVGlc) was also found in the same grain sample. According to the semi-quantification by LC-Orbitrap MS, more than 15% of FUX and NIV were estimated to be converted into respective glucosides. The existence of these masked mycotoxins should be taken into account in risk assessment, since they could be transformed back to the corresponding mycotoxins under certain conditions; for example, through various food processing operations or in the digestive tract of mammals after ingestion.     

Mycotoxin profiles in the grain of Triticum monococcum,Triticum dicoccum and Triticum spelta after head infection with Fusarium culmorum

BACKGROUND: The aim of study was to investigate mycotoxin profiles in the grain of spring lines of Triticum monococcum (12 lines), T. dicoccum (13 lines) and T. spelta (five lines), in comparison to the T. aestivum cultivar Sumai‐3 which is resistant to Fusarium head blight. The grain was obtained from control heads and heads artificially inoculated in the field with Fusarium culmorum. Mycotoxins were determined by LC‐MS/MS. RESULTS: A total of 11 toxins were identified in control grain samples. Deoxynivalenol (DON) concentrations exceeded 0.5 mg kg^?1 in only three samples of T. monococcum grain and in one sample of T. dicoccum grain. Inoculation with F. culmorum resulted in a substantial increase in the concentrations of DON (to 63 mg kg^?1) in the T. monococcum and DON‐3‐glucoside (to 5.6 mg kg^?1) in the T. dicoccum. Inoculation contributed to a drop in tentoxin levels (by 57% in T. spelta) and to an increase of cyclodepsipeptide concentrations (in particular enniatins B and B₁) being two‐fold (T. monococcum) to four‐fold (T. dicoccum) higher on average than in control samples. The Sumai‐3 responded to inoculation with nearly a two‐fold drop in the levels of the cyclodepsipeptides. CONCLUSION: The results of a discriminant analysis for all identified toxins indicate that einkorn, emmer and spelt differ significantly with regard to the mycotoxin profiles of their grain. Copyright © 2009 Society of Chemical Industry     

Simultaneous Determination of Deoxynivalenol,Deoxynivalenol-3-Glucoside and Nivalenol in Wheat Grains by HPLC-PDA with Immunoaffinity Column Cleanup

Deoxynivalenol-3-glucoside (D3G) is a modified mycotoxin formed by the metabolism of plants through the conjugation of deoxynivalenol (DON) with glucose. Toxicology studies of D3G for human and animal health are still under investigation, and the development of practical and reliable methods for its direct determination, especially in cereal matrices, is of great importance. In the present study, a methodology for simultaneous determination of D3G, DON, and nivalenol (NIV) in wheat grains, using immunoaffinity column (IAC) cleanup, separation by C18 column and detection by ultraviolet (UV) absorption, was optimized and in-house validated. The results demonstrated adequate values of D3G recovery from IAC and spiked samples. Intraday precision, linearity, limit of detection and limit of quantification (LOQ) were also adequate for the determination of these mycotoxins. Range of applicability varied from 47.1 to 1000 μg/kg for D3G and from 31.3 to 1000 μg/kg for DON and NIV, with recovery ranging from 84.7?±?7.2 % to 112.3?±?8.1 %. A high incidence of D3G (41.2 %, all samples <LOQ) was verified in commercial samples of wheat grains and whole wheat-flour (n?=?17). Also, the presence of D3G occurred simultaneously with DON in 100 % of the D3G-positive samples. DON levels varied from <LOQ to 325.8 μg/kg, and NIV was detected in only 29.5 % (from <LOQ to 140.6 μg/kg). To the best of our knowledge, this is the first method of simultaneous determination of NIV, D3G, and DON by high-performance liquid chromatography with photodiode array detector (HPLC-PDA) reported until now.     

Effect of relative humidity on germination of ascospores and macroconidia of Gibberella zeae and deoxynivalenol production

Cereals are frequently infested by mycotoxin-producing fungi such as Gibberella zeae. G. zeae produces sexual spores (ascospores, dispersed by wind) and asexual spores (macroconidia, dispersed by rain droplets) to infect host plants. The production of the mycotoxin deoxynivalenol (DON) and the germination of ascospores and macroconidia of G. zeae were studied at 20 degrees C in relation to relative humidity (RH). The DON contents of wheat heads and autoclaved rice grain samples, artificially inoculated with ascospore or macroconidia suspensions of equal spore density, were determined at 35 days after inoculation by high-performance liquid chromatography (HPLC). The average DON production 35 days after inoculation was much lower on rice (3.95+/-1.34 mg kg(-1)) than on wheat heads (302.30+/-57.46 mg kg(-1)). Macroconidia inoculi produced more DON than ascospore inoculi at relative humidities >90%, but less DON between 53% and 80% RH. At RH < or = 53%, no significant differences in DON production were observed between macroconidia and ascospore inoculi. DON production increased with RH irrespective of spore type. Germination of ascospores and macroconidia was monitored during incubation above six constant humidity solutions ranging from 30% to 93% RH. Ascospores only required a RH > or = 53%, whereas macroconidia required RH of > or = 80% for germination. The different humidity requirements of the two spore types for germination are discussed as a potential reason for the differential DON production of ascospore and macroconidia inoculi in relation to humidity. The results indicate that DON contamination levels partly dependent upon the interaction of spore type and RH and may confer an ecological advantage to G. zeae over other Fusarium head blight pathogens.     

Stable isotope dilution analysis of the Fusarium mycotoxins deoxynivalenol and 3-acetyldeoxynivalenol

Trichothecenes are secondary metabolites produced by several fungi of the Fusarium genus during their growth period. They inhibit protein biosynthesis in eukaryotic cells resulting in numerous toxic effects such as diarrhea, vomiting, and gastro-intestinal inflammation. Considering its occurrence in food and feedstuff, deoxynivalenol (DON) is one of the most important trichothecenes. We report the synthesis of stable isotope labeled 15-d(1)-deoxynivalenol (15-d(1)-DON) from its natural precursor 3-acetyldeoxynivalenol (3-AcDON) as starting material. Furthermore, a method for the analysis of DON and 3-AcDON using HPLC-MS/MS with stable isotope labeled 15-d(1)-DON and 3-d(3)-AcDON as internal standards has been developed. In total, 18 cereal product samples were analyzed with contamination levels ranging from 10-301 microg/kg for DON and 5-14 microg/kg for 3-AcDON. This is the first report of an isotope dilution MS method for the analysis of type B-trichothecenes.     

Molecular survey of trichothecene genotypes of Fusarium graminearum species complex from barley in southern Brazil

Fusarium head blight is a disease of primary concern to small-grain cereals of Brazil, including barley. Its main causal agent, Fusarium graminearum species complex (Fg complex)¸ is able to produce mycotoxins, especially deoxynivalenol (DON) and nivalenol (NIV), that usually contaminate grain. Strains that produce DON may also produce its acetylated derivatives: 3-acetyl-DON (3-ADON) and 15-acetyl-DON (15-ADON). Ninety two isolates were obtained from samplings of barley grain during three years (2007, 2008 and 2009) from several fields in both southern and northern production regions of Rio Grande do Sul state, Brazil. These isolates were examined for polymerase chain-reaction-based (PCR) trichothecene genotype based on the amplification of portions of Tri3 and Tri12. There was no effect of year or region on the proportion of trichothecene genotypes. Overall, 66% of the strains (61/92) were 15-ADON, 4.4% (4/92) were 3-ADON and 29.3% (27/92) were NIV. The overall NIV/DON ratio estimated (0.41) was five times higher than that found in previous studies with strains from wheat grown in the same region. Species identification of nine strains representing the trichothecene genotypes, based on comparisons of DNA sequences of portions of the PHO, RED and URA genes with sequences from curated reference isolates of Fusarium from GenBank, revealed that they belong to F. graminearum sensu stricto (four 15-ADON and one 3-ADON strain), F. meridionale (three NIV strains) and F. austroamericanum (one 3-ADON strain). These results add to the current regional knowledge of trichothecene genotypes and species within the Fg complex affecting barley in the region.     

Transfer of Fusarium mycotoxins and 'masked' deoxynivalenol (deoxynivalenol-3-glucoside) from field barley through malt to beer

The fate of five Fusarium toxins--deoxynivalenol (DON), sum of 15- and 3-acetyl-deoxynivalenol (ADONs), HT-2 toxin (HT-2) representing the main trichothecenes and zearalenone (ZON) during the malting and brewing processes--was investigated. In addition to these 'free' mycotoxins, the occurrence of deoxynivalenol-3-glucoside (DON-3-Glc) was monitored for the first time in a beer production chain (currently, only DON and ZON are regulated). Two batches of barley, naturally infected and artificially inoculated with Fusarium spp. during the time of flowering, were used as a raw material for processing experiments. A highly sensitive procedure employing high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was validated for the analysis of 'free' Fusarium mycotoxins and DON-conjugate in all types of matrices. The method was also able to detect nivalenol (NIV), fusarenon-X (FUS-X) and T-2 toxin (T-2); nevertheless, none of these toxins was found in any of the samples. While steeping of barley grains (the first step in the malting process) apparently reduced Fusarium mycotoxin levels to below their quantification limits (5-10 microg kg(-1)), their successive accumulation occurred during germination. In malt, the content of monitored mycotoxins was higher compared with the original barley. The most significant increase was found for DON-3-Glc. During the brewing process, significant further increases in levels occurred. Concentrations of this 'masked' DON in final beers exceeded 'free' DON, while in malt grists this trichothecene was the most abundant, with the DON/DON-3-Glc ratio being approximately 5:1 in both sample series. When calculating mass balance, no significant changes were observed during brewing for ADONs. The content of DON and ZON slightly decreased by a maximum of 30%. Only traces of HT-2 were detected in some processing intermediates (wort after trub removal and green beer).