Effect of cultivation conditions and electrolyzed hydrogen water treatment on black staining in ‘Taishu’ persimmon fruit

The ‘Taishu’ persimmon is a PCNA cultivar bred at the Institute of Fruit Tree and Tea Science, National Agriculture and Food Research Organization, Japan. It is a good cultivar with large fruit and high sugar content and is characterized by a crispy texture. However, when exposed to rain in autumn, the fruit surface is oxidized and turns black, resulting in soiled fruits. To reduce black staining, we examined the effect of irrigation of the trees with electrolyzed hydrogen water (EHW; dissolved hydrogen 220 ppb), which has a reducing effect, as well as other cultivating factors, namely fruit bagging. Black staining was significantly suppressed when fruits were bagged to reduce the fruit surface from being wet by the rain. Young trees showed significantly less black staining on fruit peels than mature trees. Black staining was further significantly reduced by irrigating young trees with EHW. The expression of the PLDα (phospholipase) and Lox3 (lipoxygenase) genes are related to membrane deterioration and were suppressed by 37 and 33% following EHW treatment, respectively. These findings suggest that EHW treatment could reduce the deterioration of biological membranes by enhancing the reducing properties of fruits, thereby reducing black stains on fruit peels, and could be effective against physiological disorders of fruit trees.