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The occurrence of the mycotoxins deoxynivalenol (DON) and ochratoxin A (OTA) in the winter wheat of 1997 and 1998 grown under organic farming conditions was investigated using ELISAs (R-Biopharm) for quantification. The influence of delayed drying of the grain after harvest on the development of DON and OTA was determined in storage trials (moisture: 17% and 20%; temperature: 20 degrees C; duration: four and six weeks). The Tox5 PCR assay was used both to detect Fusarium species with the potential to produce trichothecenes and as a measure of their relative DNA content during the storage trials. The intensity of the PCR signals was correlated with the DON concentration. Fusarium species were identified microscopically by standard methods. All the freshly harvested grain samples were contaminated with DON and showed further increases in the DON concentration during storage. OTA contamination was found in 14.3% of the 1997 samples and in 24.1% of the 1998 samples. OTA increased during storage trials of the 1997 samples but not in the 1998 samples.

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Sulfur speciation in low molecular weight (LMW) subunits of glutenin after reoxidation with potassium iodate and potassium bromate at different pH values, aged subunits of glutenin as well as gluten, and gliadin have been investigated in situ by S K-edge X-ray absorption near-edge structure (XANES) spectroscopy. XANES spectra were analyzed quantitatively using a least-squares fitting routine to provide relative percentage contribution of different sulfur species occurring in the samples. Using potassium iodate and potassium bromate for reoxidation of reduced LMW subunits of glutenin led not only to disulfide states but also to higher oxidation states (sulfoxide state, sulfonic acid state). Strongest oxidation occurred at low pH values. Higher oxidation states were also predominantly detected in the aged subunits of glutenin, whereas the disulfide state was the main sulfur species in gluten and gliadin samples. The results showed that the oxidation state of sulfur prior to oxidation (thiol, disulfide) strongly influences sulfur speciation after oxidation. The choice of the oxidizing reagent seems to be of minor importance.

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