Determination of green pea and spinach adulteration in pistachio nuts using NIR spectroscopy

Pistachio is often subjected to adulteration due to its high demand and economic value in desserts such as baklava and confectionary products. Green peas and spinach are the most used adulterant instead of pistachios because of their organoleptic properties, color similarity and cheapness. The purpose of the present study was to develop a technique for the determination of green pea and spinach adulteration in pistachio nut by near infrared (NIR) spectroscopy coupled with chemometric analysis. Within this scope, green peas and spinach samples were mixed with pistachio nuts at concentrations between 20% and 80% (w/w) with 20% increments. NIR spectra of pure and mixed samples were acquired between 908 and 1695 nm. Principal component analysis (PCA) model was developed successfully to discriminate pure and adulterated samples. Two partial least squares regression (PLSR) models were developed to predict green pea and spinach adulteration rates with R² and root mean square error of prediction (RMSEP) values which were found as 0.9957 and 7.87 for green pea and 0.9968 and 4.69 for spinach, respectively. The obtained results showed that NIR spectroscopy is a non-destructive, fast and straightforward method for classification and determination of pistachio adulteration with green pea and spinach.