The Sanitizing Effect of Peracetic Acid on Microbial Contamination of Pistachio (Pistacia vera L.)

The economic importance along with the high nutritional value of pistachio has necessitated further research on this agricultural product. Its contamination with various microorganisms causes several problems for the production, consumption and export of pistachio every year. Pistachio as a fatty nut is very susceptible to fungal and bacterial contamination and thereby, its shelf life would be reduced. Peracetic acid is a strong oxidizer which can rapidly remove a wide range of microorganisms and is also environmentally safe. In this research, pistachio seeds were firstly treated with different concentrations (0, 1, 2 and 2.5%) of peracetic acid for 0.5, 1, 1.5, 2 and 5 min. Then the growth of fungi and bacteria were evaluated. The results indicated that 2% peracetic acid for 0.5 min led to 99% reduction in contaminating microflora . In the next step, the most common microflora contaminating pistachio seeds were detected and exposed to different concentrations of peracetic acid for 0.5, 1, 1.5, 2 and 5 min. The results showed that 1% peracetic acid for 0.5 min inhibited the growth of the dominant microflora more than 99%. Peracetic acid treatment in the tested range had no significant effect on lipid content but reduced peroxide value. Therefore, disinfection of pistachio product with a concentration of 1-2% peracetic acid in the washing basins of pistachio processing terminals may be  an applicable approach to inhibit their microbial (bacteria and fungi) contamination up to 99% and improve their quality before introducing to the market. However, this idea requires further field research.