Eri Inoue, Haruka Kobayashi, Fumie Saito, Masashi Hisamoto, 
and Tohru Okuda*  
*University of Yamanashi, 13-1, Kitashin 1-chome, Kofu, Yamanashi, 4000005, Japan (okuda@yamanashi.ac.jp)

Tannins and anthocyanins are important components of red wine and their extraction mechanisms have been studied intensively. In general, red wines with a deep reddish color are considered better than those with light color. There are two types of grape tannin, originating from skin or from seed. Skin tannin has a more positive effect on wine taste than seed tannin, but the skin tannin concentra-tion decreases during fermentation. Polyphenol from red grape skin can adsorb to insoluble polysaccharides and we hypothesize that this is one cause of polyphenol reduction during fermentation. We investigated the conditions under which tannin adsorbs to grape insoluble polysaccharides. Sample grape polysaccharides were separated and purified from skin, seed, and pulp and were subjected to model experiments with grape tannin. Grape tannin adsorbed to all parts of grape polysaccharide under the same conditions, but the adsorption rates were different. For example, in Muscat Bailey A, the adsorption rate was 5% in pulp, 30% in skin, and 45% in seed. Seed insoluble polysaccharide showed the highest affinity with grape tannin. The results indicate the importance of the conditions under which they react with each other.

Funding Support: JSPS KAKENHI