Abstract: Objective: To explore the quality changes of tarocco blood orange No. 3 during on-tree storage, establish a comprehensive evaluation system, and recommend the optimal harvest time based on the system. Methods: Oranges were sprayed with 2,4-dichlorophenoxyacetic acid (2,4-D) sodium salt and evaluated for conventional quality indexes, pesticide residues, volatile aroma components, flavonoids and phenolic acids contents after different periods of on-tree storage. Comprehensive evaluation of the samples with different storage periods was performed using principal component analysis (PCA) and factor analysis. Results: In the 14 samples with different storage times, limonene accounted for the highest proportion of the total volatile aroma components, neohesperidin accounted for the highest proportion of the total flavonoids, and ferulic acid accounted for the highest proportion of the total phenolic acids. There were significant differences in quality indexes, volatile aroma components, flavonoids and phenolic acids contents among these samples. Comprehensive evaluation and pesticide residue analysis showed that blood oranges exhibited the best flavor and palatability as well as the lowest safety risk when kept on the tree for 49 days. Conclusion: This study recommended that the best harvest time for tarocco blood orange No. 3 is the end of March each year, thereby providing data support for prolonging the citrus market period and regulating the flavor, palatability and safety of citrus fruits.

Key words: blood orange No. 3; on-tree storage; comprehensive evaluation; optimal harvest time