Effect of temperature, relative humidity and moisture on aflatoxin contamination of stored maize kernels

Moses Okoth Marenya, Tilahun Seyoum Workneh, Francis Collins Muga

Abstract: This study investigated the aflatoxin contamination of maize kernels for selected temperature, relative humidity and moisture content levels. Samples of maize kernels at moisture content levels of 14, 15, 16, 18, and 20% (wb) were inoculated with Aspergillus flavus spores and incubated in a climatic test chamber for ten days at 20°C and 30°C, and relative humidity of 60% and 90%. The results indicated that aflatoxin contamination was significantly (p ≤ 0.05) affected by temperature and relative humidity whereas moisture content had no significant (p > 0.05) effect. Aflatoxin contamination occurred at both 20°C and 30°C. The production of aflatoxin was pronounced at 30°C, ranging between 0.3 μg.kg-1 – 11179.7 μg.kg-1, compared to 20°C that ranged between 0.8 μg.kg-1 – 733.7 μg.kg-1. Relative humidity of 90% had higher levels of aflatoxin contamination of between 3.9 μg.kg-1 – 11179.7 μg.kg-1, while a relative humidity of 60% had levels of aflatoxin contamination of between 0.3 μg.kg-1 – 2.4 μg.kg-1. The interaction between temperature and relative humidity significantly (p ≤ 0.05) influenced aflatoxin contamination of maize. However, the interaction between temperature and moisture content, moisture content and relative humidity, as well as the combined interaction of temperature, moisture content, and relative humidity had no effect on the level of aflatoxin contamination. The results indicate that the level of aflatoxin contamination at a relative humidity of 60% was lower than 5 μg.kg-1. Consequently, maintaining storage conditions at a relative humidity level of less than 60% results in minimal aflatoxin contamination of maize kernels, thus assuring its safety for consumption.

Keywords: aflatoxin; Aspergillus flavus; maize; storage

Date published: 2019-04-02