Relationships between Surface Blushing and Qualitative Components of Japanese Apricot (Prunus mume Sieb. et Zucc.) ‘Nanko’ Fruit

The relationships between surface blushing and the content of qualitative components of the Japanese apricot ‘Nanko’ fruit were investigated. Brightly blushed fruit covering over 25% of its surface had higher levels of citric acid, phenolics, and antioxidant activity in its flesh than non-blushed fruit. Shading apricot fruit from ultraviolet (UV) light for about 3 weeks before harvest produced a clear decrease in surface blushing, phenolic content, and antioxidant activity. UV-B irradiation for 12 h to the inner canopy fruit 10 days before harvest resulted in blushing and increased the antioxidant activity. These results showed that brightly blushed fruit was rich in phenolics and antioxidant activity and that UV light played an important role in blushing, phenolic content, and antioxidant activity in the Japanese apricot ‘Nanko’ fruit. When fruit shaded from sunlight was exposed to sunlight for about 3 weeks before harvest by cutting off the shoot with leaves around the fruit to increase UV irradiation, surface blushing was caused, and the phenolic content and antioxidant activity in flesh were increased. On the other hand, placing reflecting films under the outer canopy for 40 days had no effect on the development of the bright red color.