Influence of inoculum size of Aspergillus flavus link on the production of aflatoxin B 1 in maize medium before and after exposure to combination treatment of heat and gamma radiation

Abstract

Vegetative growth of Aspergillus flavus Link NRRL 5906 was independent of inoculum size. Reduction in inoculum size by serial dilution (3–4 log cycles) resulted in 3–12 fold increase in aflatoxin production. Irradiation with 3.5 kGy reduced inoculum size by 3–5 log cycles and resulted in enhanced aflatoxin B 1 production but this effect was similar to the effect obtained by dilution of unirradiated spores. It is concluded that aflatoxin B 1 formation is inversely related to the inoculum size of A. flavus NRRL 5906. Maximum accumulation of aflatoxin B 1 was generally in 4 days in amended maize meal broth and 8 days in maize meal broth. A combination of moist heat (60°C for 30 min under > 85% R.H.) and 4.0 kGy of gamma irradiation inhibited aflatoxins production in flasks containing either broth.