Phenolic compounds of grape stems and their capacity to precipitate proteins from model wine

Reintegration of grape stem, a by-product from wine production, into the food chain is of high interest from an economic and environmental perspective. Therefore, an investigation of stems was undertaken and is described here. It is known that quality of stems is of high variability. In this study the stems from four grapevine varieties (Syrah, Cabernet Sauvignon, Merlot and Chasselas) cultivated in Switzerland were treated in following ways: drying, cutting and separation into fractions based on particle size. All fractions were then characterised for their phenolic compounds content. It was found that Chasselas fractions contained most phenolic compounds. The addition of grape stems of the four different varieties allowed reduction of the protein content of a model wine. The extent of protein precipitation was highly correlated with the amount of phenolic compounds in stems added. Among the examined varieties, Chasselas brought most promising results, with the high reduction of the protein at low level of stem addition.