Interactive Effects of Spore Load and Temperature on Aflatoxin Production1

Abstract

The relationship between initial spore load of an aflatoxigenic mold and subsequent growth and aflatoxin production were studied at 28 and 35°C. The initial spore loads ranges <101 to 107 spores/ml. As the spore level increased, visible growth appeared sooner and was more extensive. Growth, determined by viable plate counts, indicated that maximum growth in all the treatments reached 109 CFU/g, irrespective of the initial spore load. Mycelial growth and sporulation occurred faster at 35°C at all spore levels than at 28°C. At 28°C, unusually high amounts of aflatoxin Bl (380 ug/g) were produced when 103 spores were inoculated into 50 g rice, while the lower and the higher spore levels produced comparatively lower levels of aflatoxin. At 35°C the lowest spore level (<101 spores) produced the highest amount of aflatoxin B1 (62 μg/g). The higher spore levels at 35°C either did not result in any aflatoxin formation, or the amounts produced were negligible. At 35°C many fluorescing compounds other than aflatoxins were detected.