Influence of Different Moisture Contents and Temperature on Growth and Production of Aflatoxin B1 by a Toxigenic Aspergillus flavus Isolate in Wheat Flour

Experimental short time population and production of aflatoxin B1 by Aspergillus flavus in wheat flour at 20, 25, 30, 35 and 40oC, as related to different moisture contents 5%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22% and 25%, was studied. Spore suspension of a toxigenic A. flavus containing ~ 3×10 spore/ml was inoculated in each flask containing 50 g wheat flour and incubated for 15 days. Spore count was observed slightly in flour with a moisture content 5% at all incubation temperature, then increased gradually by rising the moisture content reaching the maximum at 30oC with moisture content 25%. High performance liquid chromatography analysis of AFB1 showed the lowest quantification (482 ng/kg) at 20oC with 8% moisture content in comparison to uninoculated control. The higher quantity of AFB1 (637835.4 ng/kg) was produced at 25oC with 25% moisture content. Accumulation of high amounts of AFB1 was noticed at 20, 30 and 35oC with moisture content 25%. However, at 40oC with moisture contents 22% and 25%, high spore count was recorded, but traces of AFB1 were produced. The significance of this investigation is that, in the event of wheat flour contamination with afltoxigenic species, rise in moisture contents are hazardous in the storage of wheat flour around 25oC.