Long-term cold storage affects metabolites, antioxidant activities, and ripening and stress-related genes of kiwifruit cultivars

Cold storage is widely used to prolong the storability of kiwifruit by delaying ripening, which would be very beneficial for its even distribution and market availability throughout the year. Maintaining nutritional quality is also equally important to fulfill consumers' preferences during distribution. Hence, this study was carried out to investigate the changes in metabolites content, antioxidant activities, and ripening and stress-related genes of green 'Hayward' and gold 'Haegeum' kiwifruit during long-term cold storage. A total of 37 primary metabolites (21 amino acids, 9 fatty acids, 4 organic acids, and 3 sugars) were identified to be altered significantly during cold storage of both cultivars. Significant changes in secondary metabolites such as total phenolics, flavonoids, and vitamin C were also observed during the cold storage of both cultivars. In addition, antioxidant activity assays showed that cold storage either maintains or increases the antioxidant activity of kiwifruit cultivars. Moreover, selected representative genes related to cell wall metabolism, ethylene biosynthesis, and stress responses were differentially expressed among cultivars and storage durations, implying the importance of inherited genetic makeup for the responsiveness of metabolites to the cold storage condition. These findings could assist in providing information for the fruit industry in developing metabolic markers for indication of storability and ripening quality of kiwifruit, which in turn benefit the postharvest decisions for storage, distribution, and marketing.