THE EFFECTS OF MILLING AND PROCESSING ON WHEAT CONTAMINATED WITH OCHRATOXIN-A

Samples of sound home-grown wheat (one hard and one soft milling) were obtained, cleaned, and gamma-irradiation used to reduce numbers of vi able naturally-occurring fungi. Each sample was inoculated with a toxi genic strain of Penicillium verrucosum and monitored for ochratoxin A formation. When ochratoxin A had reached a level of 60 mu g/kg, the sa mples were milled into ten fractions which were analysed for ochratoxi n A by an HPLC method with immunoaffinity column clean-up. Each straig ht-run white flour was baked into bread which was analysed in the same way. Relationships between ochratoxin A levels in naturally-contamina ted 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 wh ite or wholemeal flour into bread. Recoveries in the straight-run whit e flours, however, were only approximately one-third for the hard whea t and two-thirds for the soft wheat of the ochratoxin A in the unclean ed 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 whea t than from soft. Conversely, a much higher proportion of the ochratox in 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 s couring reduced the ochratoxin A level in white and wholemeal flour th ree-fold for both the hard and soft wheat.