2003 Fiscal Year Final Research Report Summary
Reduction of Bitterness and Astringency of Wine Tannins by Glycoproteins
| Project/Area Number |
14560094
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
食品科学・栄養科学
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| Research Institution | University of Yamanashi |
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Principal Investigator |
YOKOTSUKA Koki University of Yamanashi, Interdisciplinary Graduate School of medicine and Engineering, Professor, 大学院・医学工学総合研究部, 教授 (60020450)
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| Co-Investigator(Kenkyū-buntansha) |
OKUDA Tohru University of Yamanashi, Interdisciplinary Graduate School of medicine and Engineering, Associate professor, 大学院・医学工学総合研究部, 助教授 (10252008)
TAKAYANAGI Tsutomu University of Yamanashi, Interdisciplinary Graduate School of medicine and Engineering, Associate Professor, 大学院・医学工学総合研究部, 助教授 (00252007)
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| Project Period (FY) |
2002 – 2003
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| Keywords | wine / protein / polyphenol / catechin / procyanidin / bitterness / astringency |
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| Research Abstract |
Although wine soluble proteins originate in juice, seed skin and yeast, most of them originate in juice (approximately 90% of the total protein content). All the soluble proteins are glycoproteins. Our experimental and commercial white and red wines contained 29.8 to 107.1 mg/L soluble proteins, and very stable soluble proteins (13.6 to 36.4 mg/L) were detected in the wines after severe clarification and fining. Polysaccharides or polymeric tannins interacted with the proteins to form complexes or similar entities, thereby stabilizing the soluble proteins in the wines.
Glycoproteins were isolated from Semillon wine by ammonium sulfate precipitation and Sephadex G-100 chromatography. Total phenols in Semillon seeds were subjected to extraction with 50% aqueous ethanol, and four seed phenol fractions (catechin, dimeric phenols, and oligomeric and polymeric tannins) were obtained by diatomaceous earth partition chromatography of the total phenols. The glycoproteins, catechin, and dimeric phenols appeared unchanged during storage in a wine-like model solution (aqueous 10% ethanol solution of pH 3.0) at 20oC for 48 hours. However, the oligomeric and polymeric tannins, as well as the total phenols, gave rise to appreciable turbidity. The possible sensory effects of the added proteins were investigated by paired comparisons of pure compounds (catechin and dimer phenols) with the same compounds mixed with proteins. It was hypothesized that proteins would decrease the taste of the catechin and the dimer phenols by decreasing their availability to interact with the receptors. The results corroborated the hypothesis when low concentrations of phenols and proteins were used. However, a reverse trend was observed at high concentrations. It was hypothesized that the high concentration of proteins increased the total taste intensity by adding their own taste.
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