Abstract
Various preservatives, such as calcium propionate, sorbic acid, potassium sorbate, dehydroacetic acid, sodium dehydroacetate, benzoic acid, sodium benzoate and isobutyl p-hydroxybenzoate, were examined for their inhibitory effects on the growth and aflatoxin B1 production of A. flavus and A. parasiticus in sliced bread coated with peanut butter.
Bread containing each preservative was baked and sliced in our laboratory. The peanut butter containing a preservative and one hundred spores of each fungus was coated on the upper surface of a slice of bread (5.5×6.5×1.0cm), and then the slice was incubated at 28°C in a Petri dish for ten days.
Of the eight preservatives, calcium propionate and sorbic acid showed the most inhibitory effects. When bread containing calcium propionate (2.5g/kg) was coated with peanut butter containing sorbic acid (1.5g/kg), the growth was retarded by 48hr (A. flavus) and 72hr (A. parasiticus), while aflatoxin B1 production was retarded by 72hr (both fungal species) in comparison with the control without any preservative.
Further experiments were performed using nine slices of the bread with ten spores each, in the same manner as described above. Neither growth of the two fungi nor aflatoxin production was observed in these slices, with one exception, in which the fungal growth of the two species and aflatoxin production were retarded by 48hr as compared with the control.
