Effects of ultrasound treatment and concentration of ethanol on selectivity of phenolic extraction from apple pomace

Abstract

SummaryThe extraction of polyphenols from apple pomace was studied using ultrasound, ethanol/water mixtures and moderate temperatures, 20–37 °C. The extraction kinetics and extraction yields of catechin and total phenolic content (TPC) were evaluated at different times of ultrasound treatment (tu) and concentrations of ethanol (Ce). The highest extraction efficiency of TPC was observed at tu = 30 min, Ce = 50% and total extraction time of te = 60 min. The high selectivity of catechin extraction was demonstrated by analysing the relative content of catechin (R = Cc/TPC) in dependence of applied extraction protocol. The initial portions of extracts at small levels of TPC (≤50 mg per 100 DM) were richer in catechin content (R ≈ 15%–31%), whereas the last portions of extracts with high level of TPS were more exhausted in catechin (R ≈ 2%).