Separating grape pomace before fermentation and restructuring the skin-to-seed ratio: A new scientific approach

The restriction of poor-quality grapes makes it difficult to obtain high-quality red wine in some regions. To compensate for wine quality deficiencies, this study constructed a new scientific approach via separating grape pomace before fermentation and restructuring the skin-to-seed ratio during maceration. The effects of the skin-to-seed proportion on the phenolic composition, color, and sensory characteristics were evaluated. The results showed that the increase in seed proportion can address deficiencies in flavanol and total phenol contents, whereas the addition of skin is useful when anthocyanins and color parameters are required to be improved. The moderate increase in the skin-to-seed ratio was responsible for the increase in some individual phenols beneficial for wine quality, including resveratrol, chlorogenic, quercetin, and catechin, etc. In general, restructuring the skin-to-seed proportion can regulate the polyphenol composition and color and compensate for wine quality deficiencies. Practical applications This research developed a new scientific approach by separating grape pomace before fermentation and restructuring the ratio of grape skin-to-seed during fermentative maceration. The utilizing of the new technique increased the contact area between the skin, seed, and juice and controlled the extraction of compounds from the solid parts into the wine. The corresponding phenolic profile, color, and sensory characteristics can be regulated. The new winemaking technique is highly suited for addressing deficiencies in anthocyanins and color. Overall, restructuring the proportion of skin and seed in maceration can compensate for wine quality deficiencies and regulate polyphenol composition and color.