A two-step biocatalytic process to extract and to acylate anthocyanins: a sustainable approach for red grape pomace biorefining

Grape pomace represents an abundant source of anthocyanins displaying coloring and health-promoting properties for food applications. At the industrial stage, the extraction of anthocyanins from grape pomace consumes solvents and/or sulfites, which are no longer desirable due to environmental issues and consumer demands. Furthermore, anthocyanins extracted from grape pomace are simple (non-acylated) O -glucosides lacking chemical stability. In this study, a two-step biocatalytic approach was developed to extract anthocyanins from grape pomace and esterify their glucosyl moiety. Different enzymes and conditions were compared for anthocyanin extraction. The highest amount of extracted anthocyanins was 1.44 g/kg fresh pomace after three sequential extraction steps with the enzyme Lysis Elite in water - ethanol (4:1). The purified anthocyanin extract was further acylated with N435 lipase in the presence of lauric acid or dihydroferulic acid, reaching acylation yields of 19.8 ± 0.7 % and 8.5 ± 1.7 %, respectively.