Influence of γ-irradiation and maize lipids on the production of aflatoxin B1 by Aspergillus flavus

The effect of gamma-irradiation and maize lipids on aflatoxin B, production by Aspergillus flavus artificially inoculated into sterilized maize at reduced water activity (a(w) 0.84) was investigated. By increasing the irradiation doses the total viable population of A. flavus decreased and the fungus was completely inhibited at 3.0 kGy. The amounts of aflatoxin B, were enhanced at irradiation dose levels 1.0 and 1.5 kGy in both full-fat maize (FM) and defatted maize (DM) media and no aflatoxin B-1 production at 3.0 kGy gamma-irradiation over 45 days of storage was observed. The level in free lipids of FM decreased gradually, whereas free fatty acid values and fungal lipase activity increased markedly by increasing the storage periods. The free fatty acid values decreased by increasing the irradiation dose levels and there was a significant enhancement of fungal lipase activity at doses of 1.0 and 1.50 kGy. The ability of A. flavus to grow at a(w) 0.84 and produce aflatoxin B-1 is related to the lipid composition of maize. The enhancement of aflatoxin B-1 at low doses was correlated to the enhancement of fungal lipase activity.