Oil Characterization and Aflatoxin Profile of Peanut Kernel Subjected to Gamma Irradiation

Peanuts are nutritious foods, however, following harvest and storage, these nuts are prone to mycotoxin contamination. Gamma irradiation is an effective technique in postharvest pest control to kill insects and inhibit mycotoxin biosynthesis. Thus, this study aimed to investigate the effect of doses of gamma ray on oil properties and mycotoxin profile of raw peanut seeds. Seeds were exposure to gamma radiation at 10 and 25 kGy and stored at ambient temperature for 6 months compared to non-treated seeds before storage. Color, hardness, oil content, total sugar, total protein content, peroxide value (PV), malonaldehyde (MDA) and aflatoxin analysis were assessed. According to this finding, no significant differences of color, hardness, oil content, PV, MDA were found among treatments. Aflatoxin inhibition and total sugars of treated gamma irradiation peanuts at 10 kGy were higher than treated peanuts at 25 kGy.

Atoxigenic Aspergillus flavus biological control of aflatoxin contamination: what is the mechanism?

The term ‘competitive exclusion’ involving physical blockage of growth or access of the toxigenic strain to the seed target has been used to describe the mechanism of biological control of aflatoxin contamination. However, recent evidence suggests that a form of intraspecific aflatoxin inhibition requiring growth of the competing strains together during the infection process in such a way that hyphae physically interact or touch is the trigger for preventing induction of aflatoxin synthesis. This direct touch-based inhibition of aflatoxin synthesis is posited to be the mechanistic basis of biological control in this system. Evidence for this idea comes from the published observations that co-culture of toxigenic and atoxigenic strains in a suspended disc system, in which the hyphae physically interact, prevents aflatoxin production. However, growth of the same strains in the same medium in the two compartments of a filter insert plate well system, separating the atoxigenic and toxigenic strains with a 0.4 μm or 3.0 μm filter, allows aflatoxin production approaching that of the toxigenic strain alone. When the strains are mixed and placed in both the insert and the well compartments, the intraspecific aflatoxin inhibition occurs as it did in the suspended disc culture system. This further suggests that neither nutrient competition nor soluble signal molecules, which should pass through the filter, are involved in intraspecific aflatoxin inhibition. When the two strains are separated by a 12 μm filter that would allow some passage of conidia or hyphae between the compartments the aflatoxin synthesis is approximately half that of the toxigenic strain alone. This phenomenon could be termed ‘competitive inclusion’ or ‘competitive phenotype conversion’. Work of others that relates to understanding the phenomenon is discussed, as well as an Aspergillus flavus population biology study from the Louisiana maize agro-ecosystem which has biological control implications.