ABSTRACT
Non-astringent persimmon (Diospyros kaki Thunb.) paste is typically produced by treating astringent persimmon fruit with alcohol or dry ice (to remove tannins) followed by abrasion. However, considering the large yield of astringent persimmons harvested in a short time, this long, laborious method has hindered the use of persimmon paste in food processing. Herein, the addition of polysaccharides was used to produce a non-astringent persimmon paste while maintaining its quality. Among the nine evaluated polysaccharides, high- (HM) and low-methoxyl (LM) pectins, carrageenan, xanthan gum, and sodium alginate exhibited high astringency removal efficiencies. No astringency recurrence was observed after freezing when HM or LM pectin, guar gum, carrageenan, or sodium alginate were added. Moreover, the addition of HM pectin, or LM pectin, or sodium alginate prevented astringency upon heating. Additionally, guar, xanthan, tara gum, or carrageenan effectively inhibited syneresis. Thus, high-quality pastes could be easily and efficiently produced using a combination of polysaccharides.
ABSTRACT
The soluble tannins in Japanese persimmon gives it an unpleasant astringent taste, which can be removed using certain conventional methods. However, these methods are not very efficient and lead to the recurrence of astringency upon heating. Thus, the use of persimmon in processed food is severely limited. Although the effects of heating time and temperature on astringency recurrence have been explored in detail, the effect of the heating method used has not yet been clarified. Considering this, we subjected an astringency-removed paste to various heat treatments, namely, stir frying, boiling, and pressurization, and examined their effect on astringency recurrence. Soluble tannin contents were also determined, and sensory evaluation was conducted. It was observed that stir frying, which is accompanied by moisture evaporation, is superior with respect to the suppression of astringency recurrence and the prevention of syneresis compared with the other two methods. Moreover, the bright orange color and the gummy texture obtained upon stir frying are favorable for commercial purposes. Therefore, it is expected that these findings will lead to the significant improvement of astringent persimmon processing.
