Contamination of Stored Pistachios to Aspergillus Section Flavi and Aflatoxins

Contamination of stored pistachio nuts to Aspergillus section Flavi and aflatoxins (AFs) as well as effective parameters on fungal growth and AF production during storage was assayed.

Twenty one pistachio nut samples were taken from some warehouse of Damghan county. Different parameters of storage, including temperature, relative humidity, and pest infestation were recorded. Contamination to aflatoxigenic fungi was investigated by serial dilution method and aspergillus flavus and parasiticus agar (AFPA) medium with three repetitions. Thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) method were used to measure quality and quantity of the produced AFs, respectively.

There was a significant difference in contamination to Aspergillus section Flavi between different samples on the basis of statistical analysis. There was no significant difference between samples contamination to Aspergillus section Flavi and storage parameters. The ability of AF production of isolates was variable. More than 88% of isolates were able to produce one or several types of AFs and less than 12% of isolates produced no AF. HPLC assay showed that out of 21 pistachio nut samples, 3 samples were contaminated with various types of AFs, but were below the allowable levels (P ≤ 0.05).

Despite the population of aflatoxigenic strains in the mycoflora of warehouse, AF contamination of pistachios was estimated to be about 14%, which was also less than the allowable level. The results showed that the environmental parameters required for the production of AF in the warehouse of Semnan province do not exist and the storage conditions in this province are suitable.