# Maize-cob study detects mycotoxins beyond visible mould

> Researchers examining 35 visibly mouldy white maize cobs in Malawi found toxins in neighbouring sections. The authors support separating affected cobs before shelling and identify limits to what the spatial measurements explain.

URL: https://foodradar.org/maize-cob-mycotoxins-visible-mould-and-trimming-limits
Language: en
Author: FoodRadar Editorial
Published: 2026-10-19T06:00:10.000Z
Updated: 2026-10-22T21:35:52.108Z
Source publication date: 2026-08-11
Category: Food safety
Türkçe: https://foodradar.org/tr/maize-cob-mycotoxins-visible-mould-and-trimming-limits
Español: https://foodradar.org/es/maize-cob-mycotoxins-visible-mould-and-trimming-limits
Deutsch: https://foodradar.org/de/maize-cob-mycotoxins-visible-mould-and-trimming-limits
Italiano: https://foodradar.org/it/maize-cob-mycotoxins-visible-mould-and-trimming-limits
Русский: https://foodradar.org/ru/maize-cob-mycotoxins-visible-mould-and-trimming-limits

## Toxins were detected in neighbouring sections

A study in Mycotoxin Research found detectable total fumonisins and deoxynivalenol in at least one section beyond the visible mould margin in each of 35 affected white maize cobs. Bertha Kachala, Limbikani Matumba and Lindy J. Rose examined cobs selected from smallholder fields in Malawi's Lilongwe district; cultivar identity was not recorded.

The researchers analysed kernels from the visible mould margin and from neighbouring positions halfway and three-quarters of the distance from that margin to the cob tip. All 35 cobs contributed the first two positions, and 28 contributed the third, giving 98 section observations. Mycotoxins were measured by liquid chromatography–tandem mass spectrometry.

## The reported shares describe measured concentrations

Neighbouring sections accounted for 15.6% of the summed measured concentrations of total fumonisins, 10.6% of deoxynivalenol, 22.2% of zearalenone and 7.8% of nivalenol. The visible mould margin accounted for the remaining shares. The authors calculated these proportions from concentrations across sampled positions; section masses were not recorded.

Aflatoxin B1 was detected in three of the 98 sections, including one neighbouring section. The main co-occurrence analysis concerned fumonisins, deoxynivalenol, zearalenone and nivalenol. Multiple toxin groups frequently occurred together in neighbouring material, and some neighbouring sections contained higher concentrations than the corresponding visible mould section.

## Spatial patterns differed between toxin groups

Across all sampled positions, the authors found significant negative associations between measured distance and deoxynivalenol, zearalenone and nivalenol concentrations. Total fumonisins showed no significant monotonic decline. In the analysis restricted to neighbouring sections, fumonisins had a significant positive fitted distance association, while nivalenol had no significant association. Concentrations did not differ significantly between the two neighbouring sampling positions.

The authors caution that these positions represented different physical distances on different cobs and that a non-significant difference does not necessarily indicate biological equivalence. The study sampled selected sections rather than a complete three-dimensional map. It could not distinguish toxin movement from hidden colonisation, separate infection points, preformed toxins or kernel-level hotspots. Missing or non-detect analytical values were treated as zero, which may have underestimated low-level contamination.

## The authors favour segregation before shelling

The authors conclude that visible mould is a useful warning signal but does not reliably mark the spatial limit of mycotoxin contamination. They support rejecting or separating visibly mouldy cobs before shelling and mixing their kernels into the grain stream, rather than trimming only the visibly affected portion for food use.

Their discussion places this measure within wider drying, storage, sorting and analytical verification, alongside practical and economic support for households and smallholders. It calls for safe, acceptable routes for rejected material and future field studies measuring toxin reduction, grain loss, economic trade-offs and behavioural acceptability.

## Sources and rights

- [Beyond the visible lesion: mycotoxin attenuation and spatial heterogeneity in maize cobs](https://doi.org/10.1007/s12550-026-00668-8?utm_source=foodradar.org&utm_medium=referral&utm_campaign=editorial&utm_content=maize-cob-mycotoxins-visible-mould-and-trimming-limits-en). Mycotoxin Research. Bertha Kachala, Limbikani Matumba and Lindy J. Rose (2026). Beyond the visible lesion: mycotoxin attenuation and spatial heterogeneity in maize cobs. Mycotoxin Research, 11 August 2026. DOI: 10.1007/s12550-026-00668-8. © The Authors 2026. CC BY 4.0. Editorial adaptation and translation: FoodRadar. [CC-BY-4.0](https://creativecommons.org/licenses/by/4.0/?utm_source=foodradar.org&utm_medium=referral&utm_campaign=editorial&utm_content=maize-cob-mycotoxins-visible-mould-and-trimming-limits-en-license).

Adapted by FoodRadar.

[Editorial standards](https://foodradar.org/editorial-policy)