Aflatoxin contamination in soybeans: role of proteinase inhibitors, zinc availability, and seed coat integrity.

Soybean trypsin inhibitors are thought to ward off pathogens. Studies with aflatoxigenic strains of Aspergillus flavus and A. parasiticus, frequent soybean contaminants, revealed that trypsin inhibitors do not affect the growth of these fungi and aflatoxin production. Further, the availability of zinc, an essential mineral for aflatoxin synthesis that was thought to explain increased aflatoxin accumulation in cooked compared with raw soybeans, was shown to decrease upon cooking. Seed coat integrity, ensuring limited access and a low moisture content, is responsible for the slow colonization of the seed by A. flavus.