Extraction of polyphenols from grape seeds by unconventional methods and extract concentration through polymeric membrane

The aim of this work was to apply unconventional extraction methods including ultrasonication (US), high voltage electrical discharge (HVED) and pulsed electric field (PEF) to extract polyphenols from grape seeds and concentrate the extracts by ultrafiltration. A comparative evaluation of the three extraction methods for release of polyphenols from grape seeds was investigated. The results show that the three methods, acting through different extraction mechanisms, have a significant effect on the size of the fragments generated and extraction efficiency. By measurements of the quantity of polyphenols released and total energy supplied, extraction efficiency was evaluated. It was shown that with the increase of energy supplied, the amounts of polyphenols released increases for all the three extraction methods. At the same energy consumption, HVED permitted higher polyphenol extraction than the other two methods. Aqueous extracts from grape seeds were processed using ultrafiltration (50 kDa) membrane to obtain fractions enriched in phenolic compounds. During clarification, extracts obtained by HVED showed the highest specific cake resistance followed by US and PEF. According to Ruth–Carman’s model, the filtration processes were governed by cake formation mechanism. The physico-chemical properties of the permeate and retentate after membrane processing were also evaluated. High retention of polyphenols in the retentate was observed.