Comparison of aqueous extraction efficiency and biological activities of polyphenols from pomegranate peels assisted by infrared, ultrasound, pulsed electric fields and high-voltage electrical discharges

Abstract

The effects of aqueous extraction of bioactive compounds from pomegranate peels using conventional extraction (CE) and extraction assisted by infrared irradiation (IR), ultrasound (US), pulsed electric fields (PEF), and high-voltage electrical discharges (HVED) have been compared. For the extractions assisted by US, PEF and HVED, the saturation in extraction was observed approximately at the same specific energy input in the order of W ≈ 90–100 kJ/kg. HVED assisted extraction enhanced the recovery of polyphenols by ≈3 and ≈1.3 times as compared to US and PEF assisted extractions, respectively. Scanning electron microscopy (SEM) data evidenced that the highest yield of total polyphenols after the HVED treatment can reflect the presence of a strong damage of the microstructure of pomegranate skins. The obtained data on inhibition of growth of A. flavus and biosynthesis of aflatoxin B1 were explained accounting for the presence of different synergetic effects of phenolic compounds on inhibition of different bioactivities. All the studied extracts (0.2 mg/mL) demonstrated the higher inhibition efficiency for S. aureus (up to ≈80%) as compared to E. coli (up to ≈33%). PEF selectively extracted and enhanced the recovery of ellagic acid (≈740 μg/g DM), whereas HVED (≈345 μg/g DM) intensified gallic acid extraction compared to US, IR, HVED and WB.