Co-fermentation of red grapes and white pomace: A natural and economical process to modulate hybrid wine composition

- Monomeric and oligomeric flavan-3-ols were significantly released from fresh WP.
- Excessive WP/RP ratio tended to decrease wine content in polymeric flavan-3-ols.
- Appropriate WP/RP ratio improved the colour stability of red wine.
- High WP/RP ratio tended to lighten the colour of red wine.
- WP addition modulated the aroma profile of WP-treated wines.

The impact of co-fermenting white grape pomace (WP) and red grape pomace (RP) on the composition of interspecific hybrid wine was studied using the Vitis sp. 'Frontenac' and 'Vidal'. The proanthocyanidin and anthocyanin content of the resulting wines were analysed by HPLC-fluorescence and UPLC-MS/MS, respectively. The CIELAB parameters and volatile compounds were analysed using spectrophotometry-UV and GC-MS-SPME, respectively. The WP addition increased the concentration of monomeric and oligomeric flavan-3-ols, and terpenes in the wines. The manipulation of the WP/RP ratio efficiently modulated the anthocyanin profile of the wines, resulting in faded red colour, a desirable achievement in hybrid red wine, which is usually perceived as too dark. An appropriate ratio (30% RP/6% WP) improved the colour stability of the wines without a significant impact on wine colour. Addition of WP proved to be a suitable tool to modulate the colour, the phenolic and volatile composition of interspecific hybrid wine.