Fungal flora and mycotoxins of six kinds of nut seeds for human consumption in Saudi Arabia

Abstract

A wide range of moulds representing several genera and species, was recorded in this study from 5 seed samples of each almond, cashew nut, chestnut, hazelnut, pistachio nut and walnut collected from different markets in Ar' Ar, Saudi Arabia. The total counts of fungi were widely fluctuated between 1960-7704 and 1948-7434 colonies/g dry seeds on glucose-Czapek's and glycerol agar media at 28 degrees C, respectively, and represented twenty genera, 53 species and 2 varieties of fungi. The prevalent fungi on the 2 agar media were Aspergillus flavus, A. niger and Penicillium chrysogenum. On glucose-Czapek's agar, Rhizopus stolonifer and Aspergillus flavus var. columnaris were isolated from all 6 kinds of nut, A. parasiticus from 5 kinds and A. fumigatus from 4 kinds with high frequencies. Eurotium species were completely absent on glucose-Czapek's agar but they were isolated in high frequency from all kinds of nut on glycerol agar medium. The different nut samples were analyzed by thin layer chromatography for the presence of aflatoxins B1, B2, G1 & G2, citrinin, ochratoxins, patulin, sterigmatocystin, diacetoxyscirpenol, T-2 toxin and zearalenone. Aflatoxins B1 & G1 were detected in 3 out of the 5 samples tested of chestnut at concentrations ranging between 20 to 60 micrograms/kg. All other samples of almond, cashew nut, hazelnut, pistachio nut, and walnut that were analyzed were mycotoxin free.