A comparison of physicochemical and ripening characteristics of golden-fleshed ‘Haegeum' and green-fleshed ‘Hayward' kiwifruit during storage at 0 °C and ripening at 25 °C

Abstract

Postharvest storage plays a key role in determining the marketability of kiwifruits. ‘Haegeum’ (Actinidia chinensis var. chinensis cv. ‘Haegeum’), a golden-fleshed kiwifruit, although gained popularity, knowledge of its postharvest qualities is limited. Here, we performed a comparative analysis of the physicochemical characteristics of golden-fleshed ‘Haegeum’ and green-fleshed ‘Hayward’ (A. chinensis var. deliciosa cv. ‘Hayward’) kiwifruit. The fruit were stored for 1, 2, or 3 months at 0 °C after harvest and subsequently transferred to a room at 25 °C for a week to induce ripening. ‘Haegeum’ had lower firmness (∼9 N lower) than ‘Hayward’ during cold storage, which was reversed during ripening, and both cultivars revealed the same firmness after a week of storage at 25 °C. ‘Haegeum’ had higher (>50 %) ascorbic acid content than ‘Hayward,’ which did not reveal significant change during the experimental period. During ripening, a spontaneous increase in respiration rate and ethylene production was observed. ‘Hayward’ had both earlier initiation and higher levels of ethylene production than ‘Haegeum’ after 2 months of storage at 0 °C followed by a week at 25 °C, which c°uld have increased the polygalacturonase expression leading to a faster softening of the fruit. Principal component analysis and heat-map of volatile compounds (VOCs) revealed distinctive changes in individual VOC profiles in both cultivars, suggesting that the VOCs in kiwifruit vary with cultivars. Based on the changes in the expression of genes related to ripening, we proposed a scheme to delineate the ripening process in kiwifruit. In conclusion, the study revealed that both cultivars have different ripening characteristics and can fetch wider marketability owing to better consumer preference. The findings also provided insights into the underlying mechanism of the ripening process in kiwifruit, which will eventually help understand and manage their postharvest qualities.