Effect of Dry Ice Removal of Astringency with Individual Packages on Shelf Life of Japanese Persimmon 'Taiten'

Abstract

　Japanese persimmon 'Taiten' is a pollination variant astringent-type cultivar with large fruits and good taste. Although the constant temperature short duration (CTSD) method for the removal of astringency in 'Taiten' has already been reported, the removal of astringency using dry ice (DI) is yet to be established. We studied the method of DI treatment after packaging the 'Taiten' with polyethylene films (individual packaging) and investigated the fruit quality during storage after removal of astringency. The application of DI at a fruit weight ratio of 0.6% was found to remove astringency in 7 days. In addition, black staining of the pericarp during storage was suppressed by individual packaging method. The flesh firmness of the inner (EI₂) and outer (EI₅) portions of the stored fruits was measured and expressed as the elasticity index (EI). The EI (EI₂ and EI₅) of the fruits that were not packaged individually (control) significantly decreased after 30 days of storage compared to the individually packaged fruits. Moreover, we measured the fruit resonance frequency ratio (f₅/f₂) during storage, which indicated the difference between flesh firmness of f₂ and f₅ regions. For the control group, the f₅/f₂ value decreased as the storage period increased. However, the f₅/f₂ value remained constant in the individual packaged fruits throughout the storage period. These results indicate that the combination of DI treatment and individual packaging can be used to store fruit for 30 days, while maintaining fruit quality.