An approach for the valorization of pomegranate by-products using ultrasound and enzymatic methods

In this work, a holistic approach for the management of pomegranate wastes towards the recovery of value-adding components, is proposed. Regarding pomegranate peels, free phenolic components were recovered from defatted material with the aid of ultrasound-assisted extraction at the optimum conditions determined in a prior work studying the effect of the used solvent (water, ethanol, methanol, 50% aqueous ethanol, and 50% aqueous methanol) on the total phenolic content, radical scavenging activity, as well as punicalagin and ellagic acid content of the obtained extracts, using various in vitro assays and RP-HPLC-DAD, respectively. In the case of pomegranate seeds, the potential of enzymatic pretreatment to enhance the recovery yield of ultrasound-assisted oil recovery was investigated. This procedure was optimized in terms of pretreatment time (60–240 min), type of enzyme (cellulase:pectinase) (0–100% cellulase), enzyme concentration (2–4% w/w), and water/seeds ratio (2–6 mL/g). The optimum efficiency achieved (27.53 g oil/100 g seeds at 1.8 h or 97.8% oil extraction) was higher to the efficiencies achieved by other recovery techniques, including maceration, ultrasound-assisted extraction, supercritical extraction cold pressing, and superheated fluid extraction at comparable or longer extraction times. Findings of the present work seem promising for the holistic valorization of pomegranate industry byproducts towards the recovery of valuable compounds as well as their future application as natural additives to functional products, minimizing, at the same time, the environmental hazard.