article · Mycotoxin Research
Visible mould is commonly used to sort and discard damaged maize, but the relationship between visible lesions and the true distribution of toxins across an ear has been uncertain. An investigation of visibly mouldy white maize cobs evaluated how toxins attenuate across distance, measuring contamination at the mould boundary and at points further along the cob. The visible mould margin contained the vast majority of the measured toxin burden across all detected compounds. However, visually clear adjacent sections still retained substantial residual mycotoxins, including fractions of total fumonisins, deoxynivalenol, zearalenone, and nivalenol. While several toxins declined significantly with distance, fumonisins did not show consistent attenuation, and multi-toxin co-occurrence persisted into adjacent tissue. Consequently, relying on visible mould lines to trim damaged areas leaves residual toxins, supporting the complete rejection of affected cobs prior to shelling.
Farmers and food handlers frequently cut away visible mould from maize cobs in an attempt to salvage grain. This research demonstrates that invisible, dangerous mycotoxin contamination spreads well beyond the visible mould lesion into seemingly healthy cob tissue. Understanding this spread helps agricultural workers and processors avoid distributing or consuming toxic grain, improving basic food safety and reducing dietary exposure to harmful agricultural toxins.
This work informs post-harvest quality control protocols and grading standards for grain aggregators, food processors, and agricultural extension services. It provides evidence-based guidance to shift sorting practices away from partial trimming to whole-cob rejection prior to shelling. The findings represent applied research that can be directly incorporated into current post-harvest handling manuals, sorting guidelines, and food safety compliance frameworks without requiring new technology development.
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Visible mould is widely used as a practical sorting cue in maize, but it remains unclear whether the visible lesion marks the boundary of mycotoxin contamination within an intact cob. This study examined mycotoxin attenuation, spatial heterogeneity, and co-occurrence in visibly mouldy white maize cobs, using measured distances from the visible mould margin. Cobs with visible mould (n = 35) were sampled for the study. For each cob, the visible mould margin was coded as 0 mm, and adjacent sections were collected at the 50% and 75% points along the measured distance from the lesion boundary to the distal cob tip, resulting in 98 cob-section observations. Mycotoxins, FUMs (FB1, FB2, FB3), deoxynivalenol (DON), zearalenone (ZEA), nivalenol (NIV) and AF (AFB1) were quantified by liquid chromatography tandem mass spectrometry. Samples with no detectable levels of mycotoxins were replaced with zero, and total FUMs were calculated (FB1 + FB2 + FB3). The visible mould margin accounted for the largest share of the measured toxin burden, accounting for 84.4% of total FUM, 89.4% of DON, 77.8% of ZEA, and 92.2% of NIV. Adjacent sections retained measurable residual mycotoxins, including 15.6% of total FUM, 10.6% of DON, 22.2% of ZEA, and 7.8% of NIV. In full-distance models, DON, ZEA, and NIV declined significantly with distance, whereas total FUM did not show significant monotonic attenuation. The AFB1 was detected in only three cob sections; these detections co-occurred with Fusarium-associated toxins. Co-occurrence analysis showed that adjacent sections frequently remained positive for multiple Fusarium-associated toxin groups, with the FUM + DON + ZEA profile persisting across measured-distance bands. These findings show that visible mould is a useful warning signal but not a reliable toxicological boundary. The results support cob-level rejection or segregation of visibly mouldy cobs before shelling, rather than lesion-level trimming, as a more defensible food-safety control measure.
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DOI: 10.1007/s12550-026-00668-8
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