Fractionation of grape anthocyanins through centrifugal partition chromatography (CPC) and evaluation of their sensory properties

Anthocyanins from grapes skins are known for their impact on red wine color whereas their involvement in mouth-feel properties, such as astringency, and bitterness has been considered less relevant in red wine. However, results suggested their involvement in sensory properties, as well as reactivity towards protein such as bovine serum albumin (BSA) and salivary protein. In this study, anthocyanin grape skin extracts from Italian cv Nebbiolo and Barbera were fractionated using Centrifugal Partition Chromatography (CPC) in three fractions, i.e. glucoside (FG), acetylated (FA) and coumaroylated (FC) anthocyanins. Gradient system described by Renault et al. (1997) was slightly modified to scale up to 1L CPC. Investigation of sensory properties was carried out for the extract and fractions throughout chemical analyses as reactivity towards BSA and salivary protein. Tasting sessions with a trained panel were performed in order to characterize anthocyanin extract and the obtained fractions. The modified CPC allowed for the fractionation of 2.5 g of skin extract per run in less than two hours reaching satisfactory level of purity for FG, whereas FA and FC required a further fractionation step on preparative HPLC. The anthocyanin extract concentration in wine-like solution showed a decrease after being treated with salivary protein, especially the glucoside and the coumaroylated anthocyanins were significantly reduced, whereas no significant interaction was found towards BSA. Fractions analysis showed a decrease in anthocyanins when treated with protein, in particular a decrease of FG and FA for salivary protein, and FG for both BSA and salivary protein. Tasting sessions in model wine solution confirmed the involvement of anthocyanins at wine-scale range in mouth-feel sensation especially bitterness.