Influence of gamma rays and sodium chloride on aflatoxin production by Aspergillus flavus

The rate of Aspergillus flavus growth and production of aflatoxin in yeast extract sucrose medium generally decreased as the concentrations of NaCl increased from 2 to 12%. Maximum production and accumulation of aflatoxin at 28 degrees C occurred after 7 days in the presence of NaCl concentrations. The number of colony forming units of A. flavus after 1.0 or 2.0 kGy irradiation was lower than in the unirradiated controls and the mould was eliminated at 3.0 kGy. Aflatoxin B1 decreased from the control level of 46 micrograms kg(-1) to 10 micrograms kg(-1) at an irradiation dose level of 2.0 kGy. Viable gamma irradiated conidia (2.0 kGy) of A. flavus showed increased sensitivity to NaCl concentrations, indicating gamma-ray injury. The levels of aflatoxin produced by 2.0 kGy irradiated conidia of A. flavus decreased in the presence of 2, 4 or 6% NaCl, and the detoxification rate was 94.1, 100 and 100%, respectively, after 21 days of incubation at 28 degrees C compared with the effect of gamma-rays or sodium chloride alone.