Carbohydrates and phenolic compounds in peel and pulp of thinned young kiwifruit (Actinidia deliciosa L. Cv. Hayward)

Abstract

Thinning application is especially recommended in kiwifruit to improve the size and quality of fruits due to excessive flowering and fruit set. Carbohydrates are allocated to high-quality fruits. This study aimed to compare the carbohydrate content and bioactive composition in the peel and pulp of young thinning fruits with mature fruits. Defect fruit was thinned at 15, 30, 45 and 60 days after the fruit set (DAFS) and compared with mature fruit as control. The maximum starch was found in young thinned fruits in 60 DAFS; thereafter, it declined to the harvest. In contrast, the highest glucose and sucrose content was found in the mature fruit. Both parts of young kiwifruit, especially 15 DAFS, presented the highest content in ascorbic acid, total polyphenol, total flavonoid and antioxidant activity. The peel exhibited the highest catechin and chlorogenic acid content, but the highest phenolic compounds in the pulp of young fruits were mostly related to gallic acid and rutin. Therefore, young thinned kiwifruits could be a source of natural functionalising ingredients with several benefits for human health. The significant amount of waste resulting from fruit thinning can contribute financially to growers with its rich contents.