Use of peanut meal as a model matrix to study the effect of composting on aflatoxin decontamination

Abstract

In developing countries, aflatoxin-contaminated peanut wastes are often used as mulching materials or soil amendments, which introduce aflatoxins and aflatoxin-producing mould into subsequent farming seasons. This research evaluated the effectiveness of composting as a means of aflatoxin decontamination using highly-contaminated peanut meal as a model matrix at 40 °C for 6 w. The composting methods caused 72.2-154.9 (41.9-75.1%), 7.4-17.6 (37.9-72.0%), 1.2-6.9 (77.1-100.0%), or 0.0-2.1 (0.0-100.0%) μg/kg reduction in the levels of aflatoxin B1, B2, G1 and G2 in peanut meal, respectively.Aspergillus flavus andAspergillus parasiticus counts and total mould counts decreased from 103-105 to <10 colony forming units/g. Composting time and the type of starters used significantly influenced aflatoxin content, while the presence of accelerator did not affect aflatoxin levels. The highest level of toxin decontamination occurred in the first week when compost temperature and ammonia concentration were high. Micronutrient contents of resulting composts were within the accepted range for fertilisers, except for calcium. Heavy metal content was below the maximum allowable levels except nickel in one of the samples. Aflatoxin reduction was also observed in an up-scale experiment using contaminated agriculture waste as raw materials. Results suggest that composting could be employed to decontaminate aflatoxin-containing agricultural waste in developing countries.