Phenolic composition of grape pomace from ‘Hasansky Sladky’ and ‘Zilga’ as affected by winemaking technology

The aim of this study was to evaluate the effect of different winemaking technologies on the phenolic composition of grape pomace from the dark-skinned hybrid cultivars ‘Zilga’ and ‘Hasansky Sladky’, grown under cool-climate conditions in Estonia. Wines were produced using white, rosé, and red winemaking technologies with varying degrees of skin contact, including short-term cold maceration, whole-cluster processing, and increased skin proportion during fermentation. Total phenolic, total anthocyanin, and total tannin content were determined in the resulting pomace. Winemaking technology significantly influenced the phenolic composition of pomace in both cultivars. In ‘Hasansky Sladky’, rosé winemaking from whole-cluster increased total phenolic content in pomace, while anthocyanins and tannins were preferentially extracted into wine. In ‘Zilga’, increased skin proportion during red winemaking enhanced the retention of total phenolics and tannins in pomace, whereas anthocyanin content was highest in pomace from white winemaking technology. These results indicate that winemaking practices primarily affect the partitioning of phenolic fractions in pomace rather than their overall presence, underscoring a strong link between production technology and the phenolic composition of grape pomace in cool-climate hybrid grape winemaking. It is decisive when evaluating pomace for by-product valorisation and product development.