Effect of Different Postharvest Drying Temperatures on Aspergillus flavus Survival and Aflatoxin Content in Five Maize Hybrids

Abstract

After harvest, maize is dried artificially to halt fungal growth and mycotoxin production while in postharvest storage. The process often limits harvest capacity and has been a frequent cause of seed injury. Higher drying temperatures could lead to shorter drying periods and faster turnover; however, there is often a deterioration of the physical grain quality, including increased breakage susceptibility and loss of viability. The goals of this study were to determine the effect of different postharvest drying temperatures on Aspergillus flavus and Fusarium verticillioides survival and aflatoxin content in maize and to determine the viability of the seed. Five corn hybrids varying in resistance to A. flavus were side needle–inoculated with A. flavus, harvested at physiological maturity, and dried at temperatures ranging from 40 to 70°C. Kernels were evaluated for aflatoxin, stress cracks, germination, and kernel infection by A. flavus and a natural infestation of F. verticillioides. Drying temperature had no effects on aflatoxin concentration given the heat stability of the toxin. With increased temperatures from 40 to 70°C, germination decreased significantly, from 96 to 27%, and stress cracks increased significantly (1.4 up to 18.7). At temperatures above 60°C, F. verticillioides kernel infection was significantly reduced to less than 18%. At 70°C, there was a significant reduction in A. flavus kernel infection, from 11 to 3%. This information is useful in determining a range of temperatures that can be used for drying seed when fungal infection, stress cracks, and seed viability are of interest.