STUDIES ON ASTRINGENCY MECHANISMS IN PERSIMMON FRUITS AND ITS APPLICATION

1998 Fiscal Year Final Research Report Summary

• Project/Area Number: 08456015
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 園芸・造園学
• Research Institution: YAMAGATA UNIVERSITY
• Principal Investigator: FUKUSHIMA Tadaaki YAMAGATA UNIVERSITY,FACULTY OF AGRICULTURE,PROFESSOR, 農学部, 教授 (90026609)
• Co-Investigator(Kenkyū-buntansha): MURAYAMA Tetuya YAMAGATA UNIVERSITY,FACULTY OF AGRICULTURE,ASSISTANT PROFESSOR, 農学部, 助教授 (20230013) ; IKEDA Mitimasa YAMAGATA UNIVERSITY,FACULTY OF AGRICULTURE,PROFESSOR, 農学部, 教授 (20007074)
• Project Period (FY): 1996 – 1998
• Keywords: persimmon / astringency / tannin / turgor / dehydration / ethanol / CO2 / acetaldehyde

Research Abstract

Firstly, we tried to isolate kaki-tannin preparation by Matuo-method, but it contained much impurity. So we isolated tannin by dialyzing methanol extract of immature persimmon fruit. The tannin so obtained, showed almost the same molecular weight as that of the original solution. Our tannin preparation almost disappeared an astringent taste by dehydration. Next, thiol-promoted degradation of the tannin polymers with sulfanylethanol was tried after artificial removal of the astringency by treatment with acetaldehyde, CO_2, or ethanol. As a result, the compounds which showed the result of the condensation of tannins with acetaldehyde was little in tannins from CO_2 and ethanol treatments, compared with that of acetaldehyde treatment. Lastly, we found water movement from tannin cells to flesh cells during artificial removal of the astringency with CO_2 or ethanol, by determination of turgor pressure in the flesh cells. These results suggest that an astringent removal with CO_2 and ethanol may come from solidification of tannins by dehydration.