Aflatoxins: Environmental Factors Governing Occurrence in Spanish Peanuts

Abstract

Aflatoxins are absent from freshly harvested peanuts although Aspergillus flavus infest most of the kernels from pods having visible openings. Microbial competition, governed by kernel moisture, limits aflatoxin content of kernels. The toxins are subject to microbial breakdown but the amount broken down is governed by initial aflatoxin concentration.

Colonization and Biochemical Changes in Peanut Seeds Infected with Aspergillus flavus1

“…Studies conducted by Cherry et al (4,6,7,8,9,10) on the effect of Aspergilli (A flavus, A. parasiticus, and A. oryzae) and other fungi (Neurospora sitophila and Rhizopus oligosporus) have shown the following changes that were distinguishable from "standard" profiles of uninoculated peanuts: Decomposition of the major storage proteins to small molecular weight components and quantitative depletion of the small protein components (4,6,7); changes in enzyme activity (10); changes in total amino acids (8); and changes in quantity of ether-soluble oil (9). Other reports (2,5,12) have shown the production of aflatoxin when peanuts are invaded by fungi. However, varying degrees of resistance to A. flavus invasion of peanut seeds has been reported.…”

Fungus Toxins Affecting Mammals

“…Factors contributing to kernel invasion by A. flavus, and production of aflatoxins, are damage suffered at harvest and afterwards, together with favorable temperature and moisture conditions during drying and storage. Ashworth, Schroeder, & Langley (15) found that at 30° C kernel moisture content of 23 to 34 per cent was optimum for growth and aflatoxin production of A. flavus in competition with other microorganisms. The precise safe upper limit of moisture to which kernels need be dried and held for storage has to be determined, but evi dence puts it somewhere within the range of 9.3 per cent (17) to 15 per cent (15) .…”

“…Aflatoxins were formed prior to harvest in kernels of pods suffering growth cracks (110). The evidence is that significant amounts of aflatoxins can be present in peanut kernels from broken or damaged pods at harvest (87), and that toxicity also develops after harvest (15). Factors contributing to kernel invasion by A. flavus, and production of aflatoxins, are damage suffered at harvest and afterwards, together with favorable temperature and moisture conditions during drying and storage.…”

Un problème d’actualité: les mycotoxicoses

“…Ash worth et ni. [4] dans leur étude sur l'influence de la teneur en eau des graines d'arachides sur la microflore contaminante, nous apprennent qu'en dessous de 12% on n'observe pas de crois sance de moisissure, qu'entre 12-35% nous obtenons une pré dominance des espèces Aspergillus (A. glaucus, A. flavus, A. niger) et Pénicillium, alors que de 35-43% on observe une flore hétérogène. Dans la prévention de la contamination fongique, on s'efforcera donc de maintenir les graines à un degré de teneur en eau suffisament bas pour éviter toute contamination.…”