Mycotoxin reduction by advanced grain cleaning solutions.

Grain cleaning is the most effective post-harvest measure to reduce high levels of mycotoxins due to the efficient removal of mould-infected grains and contaminated grain fractions on the basis of features such as size, density and optical properties. Several studies were performed during the last years to investigate the reduction of e.g. deoxynivalenol in wheat, ergot in rye, and total aflatoxins in peanuts. In this study, the reduction of total aflatoxins (AFB1, AFB2, AFG1, AFG2) in naturally contaminated maize was tested in three cleaning steps using industrial-scale cleaning Bühler machines. The first step included (i) mechanical size separation and dust removal by aspiration with the "Grain Plus", the second (ii) separation based on density differences with a "Concentrator", and the third (iii) optical sorting with "SORTEX". Four batches of maize (about 3 tons each) with different levels of aflatoxin contamination were used for the trials. Furthermore, different process settings and cleaning intensities were tested. Sampling (3 replicates/batch) was performed according to the Commission Regulation N. 401/2006 and the collected samples were analyzed by HPLC/FLD with photochemical derivatization. In addition, the incoming material was analyzed by the Eurofins' rapidust® system for on-site sampling and analysis of mycotoxins in grains. Firstly, trials once again highlighted the difficulties of sampling for aflatoxins. Samples showed a large variability with respect to aflatoxin level. However, high levels of aflatoxin contamination were observed in the removed product streams, with values up to 250 µg/kg. Consistent results were achieved by calculating the aflatoxin level of the incoming material from the removed products taking into account the mass balance. These values compared well with the analyzed levels from the rapidust® system. Aflatoxin levels were reduced from about 10 and 20 µg/kg to 3-4 µg/kg and 2-3 µg/kg for the low and high contaminated material, respectively. In conclusion, the combination of the tested cleaning machines could allow a total aflatoxin removal of 60-90% in maize.