A Novel High-Resolution Melting Method for Detection of Adulteration on Pistachio (Pistacia vera L.)

The pistachio nut (Pistacia vera L.) is a popular nut which is beneficial for health. As a result of its high price, adulteration of pistachio products with other foods is common. The green pea (Pisum sativum L.) is similar to pistachio in colour and texture when both are in a fine powder form, therefore powdered pistachio products are often adulterated with powdered green pea. In this study, we aimed to develop a novel method based on high resolution melting (HRM) to detect green pea adulteration in powdered pistachio products as low as in ratio. Novel primers that targeted the chloroplastidial sequence atpA, rpoC1 and ycf3 were tested on admixture ratios of 90:10, 99:1, 499:1 and 999:1 of pistachio:green pea. The melting temperatures (Tm) were found to detect the adulteration for the targets rpoC1 and ycf3. Since the atpA amplicons have identical guanine-cytosine content in both pistachio and green pea PCR products, it failed to distinguish the admixtures from the positive control samples. Differential plots and genotyping confidence percentages clearly distinguished the admixtures from positive controls down to a 0.1% ratio of pistachio:green pea. Sequencing of the amplicons supported the use of HRM to distinguish between pistachio and green pea. The use of HRM with novel rpoC1 and ycf3 primer sets was found to be useful for rapid, cost-effective, and reliable detection of green pea adulteration of pistachio down to a ratio of 0.1%.