Extraction and determination of volatile organic acid concentration in pomegranate, sour cherry, and red grape juices by PPy-Ag nanocomposite fiber for authentication

A solid phase microextraction fiber based on nano-sized polypyrrole-Ag (PPy-Ag) was fabricated. The size and morphology of PPy-Ag particles was characterized by scanning electron microscopy (SEM). A method based on PPy-Ag-SPME-gas chromatography (GC) was developed for determination of sour cherry and grape juice adulteration in pomegranate juice samples by determination of volatile organic acids (VOAs) concentration. The VOAs of pomegranate juice (valeric, isovaleric, lactic, and acetic acids) were extracted by fabricated polypyrrole-Ag fiber, and the concentration of VOAs was determined by GC analysis. The effects of pomegranate juice (PJ) percent, sour cherry juice (SCJ) percent, and red grape juice (GJ) percent as three variable factors on the concentration of VOAs were studied. Box Behnken Design (BBD) was applied to design the experiments that study the effect of factors on the VOAs concentration. The results showed that sour cherry and grape juice adulteration in pomegranate juice can affect the VOAs concentration, and there is a good relation between pomegranate, sour cherry, and grape juice percent and VOAs concentration. So the presented analytical method is a suitable and fast method for determination of pomegranate juice authentication.