Effect of harvest time on the chemical composition and antioxidant capacity of Gannan navel orange (Citrus sinensis L. Osbeck ‘Newhall’) juice

The present study investigates the chemical composition and antioxidant capacity of juice from the Gannan navel orange, which is harvested at one- to two-week intervals during the ripening period.  The total soluble solid (TSS), total polyphenol content (TPC), total flavonoid content (TFC), sucrose and hesperidin contents gradually increase with the ripening of the fruit, followed by slight declines at the late maturity stage.  Contrary to these observations, the contents of titratable acid (TA), vitamin C (Vc), and limonin trend downward throughout the ripening period.  However, the contents of fructose, glucose, and narirutin fluctuate throughout the harvest time.  Three in vitro antioxidant assays consistently indicate that the harvest time exerts no significant influence (P>0.01) on the antioxidant capacity.  Furthermore, principal component analysis (PCA) and Pearson’s correlation test are performed to provide an overview of the complete dataset. This study provides valuable information for evaluating the fruit quality and determining when to harvest the fruit in order to meet the preferences of consumers.  Meanwhile, our observations suggest that the fruits subjected to juice processing should be harvested at the late maturity stage to alleviate the “delayed bitterness” problem without compromising the antioxidant capacity and the flavonoid content in the juice.