Pollination-constant Non-astringent Research Articles

甘ガキと渋ガキのタンニン物質の化学的特性, 特に超遠心分離における挙動の差異について

Schlieren pattern in analytical ultracentrifugation and reactivity to acetaldehyde of tannins of Japanese persimmon fruit (Diospros kaki) were investigated using cvs. ‘Fuyu’, pollination constant non-astringent (PCNA) type, and‘Hiratanenashi’, pollination variant astringent (PVA) type.1) To study the schlieren pattern, tannins extracted from both cultivars with aqueous acetone were separated into two fractions (F-I and F-II) by size exclusion chromatography on CPG-10 2000A. After the tannin concentrations were equalised, these fractions were incubated at 40°C and subjected to ultracentrifugation at pre-incubation (0 day), 1 and 3 days of incubation. The schlieren patterns revealed that F-I and F-II fractions from both cultivars contained three or four tannin components, and that the sedimentation coefficient of each component from‘Hiratanenashi’ was larger than the corresponding component from‘Fuyu’. Moreover, the components of the F-I fraction from‘Hiratanenashi’changed or shifted remarkably during incubation; two faster components (26S and 23S) disappeared and one slower component (6S) appeared. Conversely, the components of both fractions (F-I and F-II) from‘Fuyu’and F-II fraction from‘Hiratanenashi’were stable.2) To characterize the reactivity of tannins to acetaldehyde, coagulation times of the fruit juice bathed in acetaldehyde vapor were compared between‘Fuyu’and ‘Hiratanenashi’at different tannin concentrations and pHs. A longer time was needed for coagulation as the tannin concentration became lower and when the pH value was between 3.0 and 5.0. The fruit juice from‘Fuyu’coagulated more slowly than that from‘Hiratanenashi’.The present results suggest that tannin substances from‘Fuyu’distribute mainly in a lower molecular weight range and have a milder chemical property compared with those from‘Hiratanenashi’.

Relationships of Ethanol Production by Seeds of Different Types of Japanese Persimmons and Their Tannin Content

Abstract Ethanol production in the seeds and its accumulation in the flesh were compared among 47 Japanese persimmon cultivars (Diospyros kaki L.) in relation to their degree of astringency. Those which produce relatively high amounts of ethanol and accumulate it in the flesh, i.e. pollination-variant/nonastringent (PVNA) cultivars, lose astringency on the tree, while those producing less ethanol, i.e. pollination-variant/astringent (PVA) ones, remain astringent. Pollination-constant/nonastringent (PCNA) and pollination-constant/astringent (PCA) cultivars generally produced little ethanol in the seeds and accumulated small amounts or none in the flesh. Thus, 2 different mechanisms exist that are involved in the loss of astringency. One is associated with PVNA, PVA, and PCA types and is dependent upon the production and accumulation of ethanol and presumably acetaldehyde. The second is associated with PCNA types which apparently do not produce these volatile substances.