Quality and Physiological Changes of ‘Luli’ Apple during Cold Storage

The quality and physiological changes of ‘Luli’ and ‘Gala’ apples during low-temperature storage were explored to provide a theoretical basis for the storage and preservation of new mid-early ripening apple varieties. The results showed that the hardness, soluble solids content and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity of ‘Gala’ and ‘Luli’ apples showed a downward trend during cold storage and the shelf life period. After 90 days of storage, the hardness of ‘Gala’ apples decreased by 56.3%, while that of ‘Luli’ apples decreased only by 30.7%. Compared with ‘Gala’ apples, ‘Luli’ apples had lower polyphenol oxidase and lipoxygenase activities and higher contents of total phenols, flavonoids and chlorogenic acid during storage. During low temperature storage, the contents of individual phenolics in ‘Luli’ apples decreased, and the contents of chlorogenic acid, epicatechin, hypericin, and ferulic acid decreased most in the first 15 days, but did not significantly change during the shelf life period. The contents of catechins, p-coumaric acid, rutin, and caffeic acid in ‘Gala’ apples increased slightly after 15 days of low temperature storage and then decreased, but decreased gradually during the shelf life period. The contents of all phenolics decreased during the shelf life period. The major aroma components in ‘Gala’ and ‘Luli’ apples were aldehydes, alcohols and esters, among which 3-methyl-2-buten-1-ol, isoamyl benzoate, nonanal, 2-amino-6-methylbenzoic acid, 1-methyldibenzofuran and diisobutyl phthalate were only detected in ‘Luli’ apples. During low-temperature storage, the relative contents of aldehydes in both varieties decreased, while the relative contents of alcohols and esters showed an increasing trend. The relative content of alcohols in ‘Luli’ apples decreased during the shelf life period, while the opposite trend was observed for ‘Gala’ apples. In conclusion, ‘Luli’ apples exhibited higher fruit hardness, antioxidant capacity and phenol content during low-temperature storage and the shelf life period, and the overall storage quality was better than that of ‘Gala’ apples.