Using herbal extract as a natural anti-fungal substance is an effective alternative method for application of chemical synthetic controllers in food industries due to having some certain compounds is used in food industries as a natural antimicrobial substance to decrease the microbial load and enhance taste. The main objective of this research is the application of essential oil from thyme as a natural antimicrobial substance in processing of pistachio in washing stage to decrease the microbial load and destroy aflatoxin. typical trend, various inhibitions of thyme in concentrations of 50, 100, 200, 500 and 1000 ppm in washing stage have been used. The witness group in this level was pistachios that where washed by uninhibited water. Witness and inhibited samples were analyzed to determine their mould contamination, aflatoxin generating moulds, and aflatoxin in storage. A sensory test was used to compare the color, taste, flavor, smell, and acceptance between thyme oil washed group and the witness group. According to the results, there was a significant difference between the witness sample and other samples in their fungal and aflatoxin load whereby the more the concentration of the oil was, the lower the amount of both become. In aflatoxin test, the 1000 ppm inhibition more than other inhibitions decreased the aflatoxin. Thyme oil inhibited samples in comparison to the witness sample had a more pleasant taste (thyme aftertaste) and in general featured a better acceptance; but no meaningful difference in their color and taste was observed. Also the 500 ppm inhibition was chosen as the best one, because its fungal load declined with less amount of essential oil from thyme. Based on the results, it is applicable to use the essential oil from thyme as a source of a natural antifungal substance to decrease the microbial load and specially aspergillus flavus in the washing stage of pistachio.
