Selective ultrasound‐assisted aqueous extraction of polyphenols from pomegranate peels and seeds

Abstract

In this study, the optimization of ultrasound-assisted aqueous extraction of polyphenols from pomegranate peels and seeds was conducted. A 10-min sonication (tu) pre-treatment (≈60 W) accelerated the extraction kinetics and intensified the polyphenol recovery from peels and seeds. Ultrasound pre-treatment permitted the selective recovery of polyphenols from peels by maintaining a constant concentration of the total soluble matter (°Brix) before and after sonication. Two different near-linear correlations were found between soluble matter and polyphenol extraction for the peels’ and the seeds’ extracts. Luminescence emission spectra showed significant differences between peels and seeds extracts (tu = 10 min then diffusion for 200 min) below 450 nm and above 600 nm. Ultrasound pre-treatment enhanced the quantity of the extracted molecules from peels and seeds without affecting their diversity. The optimal ultrasound pre-treatment duration was 10 min, since it ameliorated the polyphenol extraction compared to 5 min, and gave the same yield as 20 min. Practical applications Pomegranate fruits are valuable sources of bioactive compounds (vitamins, antioxidants, flavonoids, and tannins). Their processing results in the formation of byproducts containing peels (78%) and seeds (22%), discarded as waste by the food industry. Pomegranate peels and seeds are rich sources of polyphenols that have high antioxidant, anti-inflammatory, anti-allergic, antimutagenic, and anticancer properties. Ultrasound-assisted aqueous extraction of polyphenols from pomegranate peels and seeds can be used as a “green” technique to intensify the extraction of polyphenols from pomegranate byproducts. An optimized sonication time can prevent the degradation of the bioactive compounds and enhance the extraction of selective polyphenols from pomegranate peels and seeds. The extracts will then be spray dried to obtain highly bioactive powder with many industrial applications.