Comprehensive Comparison of the Nutrient and Phytochemical Compositions and Antioxidant Activities of Different Kiwifruit Cultivars in Korea

Kiwifruit is widely recognized for its rich nutritional composition and potential health benefits, yet comparative studies on different cultivars remain limited. In this study, we investigated the physicochemical properties, free sugar and organic acid content, and bioactive compounds in four kiwifruit cultivars: Hayward (HW), Halla Gold (HG), Jecy Gold (JG), and Sweet Gold (SG). This study aimed to determine variations in the composition of these cultivars and assess their antioxidant potential. The pH did not significantly differ among the kiwifruit cultivars. Sweetness and acidity are key sensory attributes in fruit, and SG exhibited the highest acidity, soluble solid content, and reducing sugar content. Accordingly, SG had the highest free sugar (11.25 g/100 mL) and organic acid (13.08 g/100 mL) levels. Phenolic acid (473.01 μg/mL) and flavonol (96.43 μg/mL) contents were most abundant in SG. In this cultivar, chlorogenic acid and epigallocatechin levels were the highest, while epicatechin and naringenin were detected only in SG. Finally, antioxidant activities (i.e., DPPH, ABTS, and hydroxyl radical scavenging activities and FRAP) were highest in SG, followed by HG, JG, and HW. The SG cultivar used in this study exhibits strong antioxidant activity, disease-suppressing effects, skin protection properties, and the potential to reduce the risk of chronic diseases due to its high phenolic compound content. These findings suggest that SG, which possesses excellent taste and functional properties, may serve as a promising candidate for the development of high-quality kiwifruit-based products.