TIME OF ASPERGILLUS-FLAVUS INFECTION AND AFLATOXIN FORMATION IN RIPENING OF FIGS

Figs in an orchard were inoculated with an aflatoxigenic Aspergillus f lavus strain in two ways by spore injection or by dusting at three mat uration stages: firm ripe, shrivelled, and dried. Fruits were individu ally examined for fungal development and analyzed for aflatoxin B-1(AF B-1) after 2, 4, 6, 8 and 10 days. Fruit injected at the first stage showed fungal development and AF B-1 contamination within two days. Th e toxin level increased sharply to 1 ppm after 10 days. The mean level of AF B-1 (284.75 ng/g) was significantly higher than those observed in other conditions. Figs dusted at the first stage showed only a tiny fungal growth even after 10 days. AF B-1 appeared after 6 days with a low frequency (35%), mean level (7.6 ng/g) and a great variation amon g figs (0.22-15 ng/g). Among fruits inoculated during the shrivelled f ig and dried fruit stages, no fungal growth was observed and AF B-1 wa s detected with a lower incidence in association with low mean levels (less than 1.25 ng/g). Methods of prevention of aflatoxin contaminatio n at the critical step, the firm ripe stage, are discussed.