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Abstract
Ascorbic acid content in kiwi fruit (Actinidia chinensis Planch, cv. Hayward) decreased by 20% when the pulp was boiled for 2 hours. Frozen samples when left to thaw at room temperature also lost ascorbic acid to an equal degree; whereas, homogenization for an hour resulted in complete oxidation of ascorbic acid to dehydroascorbic acid. Reacting polyphenoloxidase prepared from mature kiwi fruit with extracts of the same revealed that the latter contained low amounts of polyphenols. Since ascorbic acid inhibits the oxidation of many polyphenols, our finding may account for the lack of browning reaction in tissues of bruised fruits.
Abstract
‘Hayward’ kiwi fruit (Actinidia chinensis Planch.) samples collected at 20-day intervals after full bloom, May 18, until harvest in late October, were analyzed for carbohydrates, protein, organic acids including ascorbic and dehydroascorbic acids, tannins and polyphenolic substances, and cytokinin-like compounds. Starch is a predominant carbohydrate stored in the carpellary tissue which becomes hydrolyzed as the fruit approach maturity. Quinic acid was the main organic acid in young fruit which disappeared concurrently with the appearance of ascorbic acid. Mature fruit has low concentrations of tannins and polyphenolic substances but many raphides. Types of cytokinins changed as the fruit developed.