Antioxidant activity and dietary fibre of Prensal Blanc white grape (<i>Vitis vinifera</i>) by‐products

Abstract

Summary Stem and pomace of a white grape ( Vitis vinifera ) variety, Prensal Blanc, were studied for the first time: general composition and dietary fibre components together with the total soluble polyphenol content and antioxidant activity. Both by‐products present high contents of total dietary fibre (TDF), 790 g kg −1 d.m. (stem) and 716 g kg −1 d.m. (pomace). Values of the soluble dietary fibres in relation to TDF differed: 5% (stem) and 14.4% (pomace). Similar values of Klason lignin were found: 229 g kg −1 (stem) and 278 g kg −1 (pomace), however, the pomace exhibited more than twice the content of the condensed tannins (168 g kg −1 ) with regard to the stem (79 g kg −1 ). Notable were the high resistant protein contents of both by‐products. Stem and pomace showed appreciable amounts of total soluble polyphenols (87 g kg −1 against 35 g kg −1 respectively). The free radical scavenging capacity of the former by‐products was determined using the 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH) method, obtaining EC 50 values of 0.79 g d.m. g −1 DPPH (stem) and 1.32 g d.m. g −1 DPPH (pomace). These data shows that both vinification by‐products from the Prensal Blanc variety are a good source of dietary fibre and have antioxidant properties.