EFFECT OF FOOD PRESERVATIVES ON FUNGAL INTERACTION AND AFLATOXIN PRODUCTION

The effectiveness of potassium sorbate as a preservative for stored corn at 18, 24, and 30% moisture contents was studied. Growth and aflatoxin production by Aspergillus parasiticus decreased with increasing levels of sorbate treatment. The sorbate was more effective on corn with lower moisture contents and in sealed containers. The effect of potassium sorbate on growth and aflatoxin production by aflatoxin producing molds was studied in the presence of selected competing molds in yeast extract sucrose (YES) broth which were separated by a dialysis membrane (MWCO 12,000). Growth of competing molds reduced growth and aflatoxin production by aflatoxin producing molds. The colonizing ability of aflatoxin producing molds in the presence of competing molds was studied on the surface of corn meal agar or corn kernels. Aspergillus flavus was more competitive on damaged corn kernels with 18% moisture than on undamaged kernels with 26% moisture. Aspergillus niger was the competing mold most effective in reducing growth and aflatoxin production by aflatoxin producing molds in YES broth with or without sorbate treatment. The presence of A. niger and sorbate had an additive effect in reducing aflatoxin production. A. niger was most competitive in YES broth containing 0.25% yeast extract and 20% sucrose. Neither of the aflatoxin producing molds were competitive in glucose ammonium nitrate broth in all compositions studied. Potassium sorbate, calcium propionate, and natamycin were applied to non-sterilized corn kernels containing inoculated spores of A. flavus. All treatments increased the number of corn kernels dominated by A. flavus. Aflatoxin production was reduced by potassium sorbate and calcium propionate at the 0.4% level. When A. flavus and A. niger were inoculated on autoclaved corn, only treatment with potassium sorbate reduced the number of kernels dominated by A. flavus. Aflatoxin production was reduced by 0.2 and 0.4% sorbate, and 0.4% calcium propionate