Prevalence of Aflatoxin in Rafsanjan Processed Pistachios During 2011-12, And Its Relation With Time of Harvest

Contamination of pistachio nuts of Aspergillus species and their toxins is the most serious health threat for human and animal. Sorting out contaminated pistachios is critical to reduce the sources and levels of aflatoxins in pistachio nuts. Distribution of aflatoxin in processed pistachios was determined in the fifth and twentieth of September and fifth of October.

Samples were collected from dried sinking (final, small, and yellow shell discoloration pistachios) and floater pistachios. The final and small pistachios were categorized in stained, deformed, and non-stained (healthy) pistachios, while the yellow shell discoloration and floater pistachios were divided into deformed, stained, and yellow shell discoloration. Aflatoxins in the samples were measured using high performance liquid chromatography (HPLC) method.

Overall, there was significant differences (p=0.05) between aflatoxin amounts in evaluated pistachios. The results showed that the presence or frequency of deformity and shell staining in pistachio offered to the markets are critical factors and their aflatoxin B1 content ranged from 0.76 to 251.6 ng/g and 1.46 to 85.3 ng/g, respectively. In small pistachios, aflatoxin levels varied from 1.23 to 241.55 ng/g, depending on the presence or frequency of shell staining and deformity. On the other hand, there was no relation between shell staining and aflatoxin in small pistachios. The highest content of aflatoxins belonged to yellow shell discoloration (5214 ng/g) in floater pistachios. Normally, these pistachios are sorted out by their density in floatation tanks during processing. The levels of aflatoxins increased by the time of sampling and the highest amounts were associated with sampling in October fifth. The amount of aflatoxin increased by 2 to 30 times in delayed harvesting pistachios.

The results could be applied to sort out contaminated pistachio as well as early harvest to reduce the risk of aflatoxin in pistachios.