The effects of milling and processing on wheat contaminated with ochratoxin A

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Abstract
Samples of sound home‐grown wheat (one hard and one soft milling) were obtained, cleaned, and y‐irradiation used to reduce numbers of viable naturally‐occurring fungi. Each sample was inoculated with a toxigenic strain of Penicillium verrucosum and monitored for ochratoxin A formation. When ochratoxin A had reached a level of 60 μg/kg, the samples were milled into ten fractions which were analysed for ochratoxin A by an HPLC method with immunoaffinity column clean‐up. Each straight‐run white flour was baked into bread which was analysed in the same way. Relationships between ochratoxin A levels in naturally‐contaminated wheat and the products of milling and baking were established. The recovery of ochratoxin A in wholemeal compared with the cleaned wheat was essentially complete and no significnt loss occurred on baking white or wholemeal flour into bread. Recoveries in the straight‐run white flours, however, were only approximately one‐third for the hard wheat and two‐thirds for the soft wheat of the ochratoxin A in the uncleaned wheat. The reason for this was that a much higher proportion of the ochratoxin A was found in the bran and offal fractions from hard wheat than from soft. Conversely, a much higher proportion of the ochratoxin A was found in the reduction flour from soft wheat than from hard. Scouring was examined as a possible method of decontamination of wheat prior to milling. This process removes a proportion of the pericarp (bran coat) prior to milling. The results of the study confirmed that scouring reduced the ochratoxin A level in white and wholemeal flour three‐fold for both the hard and soft wheat.