Differences in Storage Quality and Phenolic Composition of Mid-Early Maturing Apple Varieties

Mid-early maturing apples can enrich the fruit market and constitute an important part of the apple industry. It is of great significance to study the quality and storage characteristics of mid-early maturing apples. In this study, ‘Luli’ and ‘Luyan’ apples as well as their parental variety Gala (as a control) were investigated for differences in their storage quality and phenolic composition. The results showed that ‘Luli’ apples had higher soluble solid content (SSC) and skin a* value and better appearance quality compared with ‘Gala’ apples, being suitable for fresh consumption. However, ‘Luyan’ apples possessed high total acid content and low solid/acid ratio, produced a largest amount of ethylene during storage, and had poor storability. Compared with ‘Gala’ and ‘Luyan’ apples, ‘Luli’ apples had higher contents of total phenolics and flavonoids and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity, indicating stronger antioxidant capacity. The main phenolics in apples varied depending on the variety, maturity and fruit part. Chlorogenic acid was the most abundant phenolic compound in ‘Luli’ and ‘Gala’ apples, while epicatechin was the most abundant phenolic compound in ‘Luyan’ apples. The content of phenols in the peel was higher than that in the pulp. Correlation analysis and principal component analysis showed that fruit firmness had a significant negative correlation with a* value (P < 0.001), and SSC had a significant positive correlation with the contents of total phenolics, total flavonoids, chlorogenic acid and DPPH radical scavenging capacity (P < 0.001). Principal component 1 (PC1) is mainly determined by the content of total phenolics, total flavonoids, chlorogenic acid, and epicatechin. Mature ‘Luli’ and ‘Gala’ apples are relatively similar in PC1. This study provides a reference for the preservation and processing of mid-early maturing apples.