Science Snippets!

Mycotoxins (e.g. aflatoxin, fumonisin, ochratoxin, vomitoxin, and zearalenone) are potent toxins synthesized by fungi growing in infected cereal crops. Presence of mycotoxins at high concentrations can impede livestock feed intake and can be lead to adverse health effects in humans. Wheat has been milled to flour for centuries, first by hand, then by stone powered by wind or water, and now by rollers powered by electricity. We know from the scientific literature that processing (e.g. extrusion) of cereal grain can lead to a reduction in certain mycotoxins (e.g. vomitoxin).

Palpacelli et al. (2007) performed an interesting study on the effect of two different types of milling (stone or roller) on vomitoxin (DON) and zearalenone (ZEN) content in soft wheat. They hypothesized that milling could affect vomitoxin and zearalenone content since previous literature has shown that these toxins are generally found in the pericarp of the wheat kernels. Milling of course removes the pericarp of wheat kernels. Palpacelli et al. (2007) milled wheat either by stone or by metal roller. In their experiments, stone ground wheat was milled as follows: seed was loaded in a seed box and passed through a grain sieve, then a trimming machine with aspirator, followed by a seed winnower, to then be passed on the milled stones (Palpacelli et al., 2007). In the roller mill, wheat was put in a sieve, tempered, and then milled by a series of roller mills.

Palpacelli et al. (2007) analyzed their wheat flour samples for vomitoxin (DON) or zearalenone (ZEN) by HPLC. The authors found that DON and zearalenone was lower in the stone-mill flour compared to the roller-mill flour. The mean DON content in the stone-mill flours was 170 ppb (parts per billion) compared with 362 ppb for the roller-mill flour (Palpacelli et al., 2007). The zearalenone content was 6.0 ppb for the stone-milled flour and 13.0 ppb for the roller-milled flour. These are interesting results. The authors hypothesize that the lower DON and ZEN concentrations in the stone-milled samples are due to the trimming machine in the stone mill that would partially eliminate the external layer (pericarp) from the wheat kernels. Secondly, Palpacelli et al. (2007) believe the DON and ZEN content to be higher in the roller mill due to the reduction rollers that are designed to extract residual flours from the bran, and this extraction might further extract the mycotoxins. Thus a HPLC analysis of DON and ZEN content of the trimming machine content (pericarp) in the stone mill system, and an analysis of the bran in the roller mill system might show where the mycotoxins end up in the two different milling systems.

Reference:

Palpacelli, V., L. Beco, and M. Giani. 2007. Vomitoxin and zearalenone content of soft wheat flour milled by different methods. Journal of Food Protection. 70:509-513.