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

Muscat Bailey A (MBA, hybrid of Muscat Hamburg × Bailey) is native to Japan and the predominant grape for making red wine in Japan. We studied the unique mechanism of phenolics extraction in MBA by comparison to that in Cabernet Sauvignon (CS). Our previous experiments revealed that anthocyanins and skin tannin were extracted during the initial period of maceration. However, their amounts decreased steeply in both CS and MBA. Seed tannin was extracted in late maceration from CS, but was extracted in very small amounts from MBA. We focused on the mechanism of the steep decrease in phenolics, which might be caused by adsorption of phenolics onto insoluble polysaccharides (IPs) in grapes. Anthocyanin, skin tannin, and seed tannin were prepared and adsorption experiments were carried out using skin, pulp, and seed IPs obtained from the same grapes. In CS, skin IPs adsorbed 12% of the anthocyanins and pulp IPs, and seed IPs adsorbed 4% of anthocyanins. In MBA, skin IPs adsorbed 20% of the anthocyanins, and pulp and seed IPs adsorbed 5 and 3% of anthocyanins, respectively. In both CS and MBA, pulp and seed IPs adsorbed less anthocyanins than skin IPs. Skin and pulp IPs adsorbed 30 and 17% of skin tannin in both CS and MBA, respectively. However, seed IPs adsorbed 18% of skin tannin in CS and 45% of skin tannin in MBA. The results suggest that grape IPs, particularly skin IPs, have high affinity to skin tannin. Skin and pulp IPs adsorbed 25% of seed tannin in both CS and MBA, but seed IPs adsorbed more than 40% of seed tannin in MBA. This strong affinity of seed IPs to seed tannin may be the reason why MBA wine has so little seed tannin.

Funding Support: JSPS KAKENHI