Mycotoxin occurrence in maize milling fractions

29-05-2013 | |
Mycotoxin occurrence in maize milling fractions
Mycotoxin occurrence in maize milling fractions

Researchers in South Africa have investigated the effect of dry milling on the reduction of fumonisins (FB), deoxynivalenol (DON) and zearalenone (ZEA) in maize. A major conclusion is that the occurrence of mycotoxin differs per milling fraction, and milling is an effective way to reduce mycotoxins in maize. The article appears in International Journal of Food Microbiology in July 2013.

Mycotoxin contamination of maize and maize-based food and feed products poses a health risk to humans and animals if not adequately controlled and managed. Five composite samples, constructed to represent different mycotoxin contamination levels, were degermed yielding degermed maize and the germ.

The degermed maize was milled under laboratory conditions and four major milling fractions (‘special’, ‘super’, ‘semolina (SEM)’ and ‘milling hominy feed’) collected. The whole maize, degermed maize and total hominy feed (germ + milling hominy feed) were reconstructed to ensure homogenous samples for mycotoxin analyses.

For comparison, commercial dry milling fractions (whole maize, special, super and total hominy feed), were collected from three South African industrial mills and analysed for the same mycotoxins, hence a more accurate assessment of the distribution between the different milling fractions. The distribution of the mycotoxins during the experimental dry milling of the degermed maize differs, with FB mainly concentrated in the ‘special’, DON in the ‘SEM’ whereas ZEA was equally distributed between the two milling fractions.

Distribution of mycotoxins between the fractions obtained during commercial dry milling generally provided similar results with the total hominy feed containing the highest and the ‘super’ milling fractions the lowest mycotoxin levels although variations existed. Milling is an effective way to reduce mycotoxins in maize, however kernel characteristics and resultant fungal colonisation may impact on the distribution of specific mycotoxins among the different milling fractions. Differences in industrial dry milling practices and problems encountered in sampling bulk maize remain a large problem in assessing mycotoxin contamination in milling fractions intended for human consumption.

Main conclusions derived from the investigations include:
•    Distribution of Fusarium mycotoxins during experimental dry milling differed between the milling fractions.
•    The total hominy feed contained the highest and the SUPER milling fractions the lowest levels of mycotoxins.
•    Distribution of mycotoxins during commercial dry milling corresponded with experimental milling.
•    Milling is an effective way to reduce mycotoxins in maize.

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