Changes in metabolites and antioxidant activities of green 'Hayward' and gold 'Haegeum' kiwifruits during ripening with ethylene treatment

Fruit ripening involves changes in physical, physiological, biochemical, and metabolic activities through the actions of enzymes and regulatory genes. In this study, we elucidate primary and secondary metabolites and antioxidant activities of green 'Hayward' and gold 'Haegeum' kiwifruit cultivars during ripening by comparing ethylene-treated fruit to the control. A total of 36 primary metabolites (20 amino acids, 9 fatty acids, 4 organic acids, and 3 sugars) were identified to be altered significantly during the ripening of both cultivars. Significant changes in secondary metabolites such as total phenols, flavonoids, and vitamin C were also observed during the ripening of both cultivars. Moreover, antioxidant activity assays showed that ripening either maintains or increases the antioxidant activity of kiwifruit cultivars. These findings could assist the fruit industry in developing metabolic markers for indication of the optimum kiwifruit ripening quality and postharvest decisions for storage, distribution, and marketing.