Changes in postharvest fruits quality from a superior line of Ziziphus jujuba‘Tailihong’seedling progeny at different maturity stages

【Objective】Ziziphus jujuba Mill., a hallmark fruit crop in China, holds significant economic and cultural value due to its dual utility for fresh consumption and drying. However, the rapid postharvest quality deterioration of fresh jujube limits its market circulation and storage duration. The physiological changes and nutrient retention in fruits postharvest are profoundly influenced by maturity stages, making the determination of the optimal harvest period a critical issue for balancing fruit quality, storability, and commercial value. Tayou 12, a superior line derived from seedling progeny of the Tailihong jujube, stands out for its stable yield, high productivity, intense sweetness, and large fruit size. Despite its outstanding agronomic traits, systematic studies on the postharvest quality dynamics of its fruit at different maturity stages remain scarce. This research aims to elucidate quality changes during ambient storage of Tayou 12 fruits at varying maturity stages, and to provide reference for precise harvest timing.【Methods】Fruits at three maturity stages, including white- ripe stage (＜5% reddening, greenwhite peel, crisp texture), half- red stage (50%-70% reddening, transitional green- red coloration), and full-red stage (＞95% reddening, physiological maturity with complete sugar accumulation), were studied. For each stage, 20 kg of intact, undamaged, disease- free fruits were stored in ventilated plastic crates at 25±1 ℃ and 75%±5% relative humidity. Daily sampling was conducted to assess water loss (gravimetric method, % ), firmness (TMS- PRO texture analyzer, N), total phenolics (Folin- Ciocalteu method, mg · g- 1 ), flavonoids (aluminum nitrate-sodium nitrite colorimetry, mg · g- 1 ), vitamin C (2,6-dichloroindophenol titration, mg · 100 g- 1 ), malondialdehyde (spectrophotometry, μmol · 100 g- 1 ), respiration rate (closed-system gas chromatography, mg·kg-1 ·h-1 ), decay rate (visual inspection, %), organic acids, and sugar profiles (HPLC, mg·g-1 ).【Results】During storage, the sensory evaluation of fruits at different maturity stages showed significant differences. The total evaluation score of the white-ripe stage was the highest at 25.3 points on the 4th day; the half-red stage (26.4 points) and the full-red stage (28.9 points) both had the highest total scores on the 1st day. After 9 days of storage, fruit at full- red stage showed the best sensory evaluation during the storage period, making it suitable for fresh consumption. After harvest, the white-ripe and half-red stage fruits increased in the red area of the peel with the increase of storage time. The half-red stage fruits turned completely red on the 7th day, indicating that the post- harvest ripening process of immature jujube fruits continued. During storage, the firmness of jujube fruits at different maturity stages decreased. The white-ripe stage fruits had the highest initial firmness (9.35 N) and the greatest degree of decline. The firmness of the full-red fruits decreased to 5.92 N on the 7th day. The firmness of the half- red stage jujube fruits was between those of the white- ripe fruits and full-red fruits. The full-red fruits had the highest initial respiration rate (35.50 mg · kg- 1 · h- 1 ), which was 2.24 times that of the white-ripe fruits (15.89 mg·kg-1 ·h-1 ) and 1.67 times that of the half-red fruits (21.28 mg·kg-1 ·h-1 ), reflecting vigorous metabolic activities. However, during storage, the respiration rate of the full-red fruits showed a significant downward trend, and became lower than that of the half-red fruits from the 5th day. The white-ripe and half-red fruits both showed respiration peaks during storage, and they had no significant difference in initial respiration rate and final respiration rate, indicating that immature fruits could maintain metabolic vitality during post-harvest storage. The water loss rate during storage increased with the increase of maturity: white- ripe stage (2.73% on the 9th day of storage)＜half-red stage (3.57%)＜full-red stage (4.92%), which was related to the stomatal density and cuticle thickness of the peel. The full-red fruits deteriorated rapidly, with a decay rate of 21.9% on the 4th day of storage, mainly due to peel softening and a decrease in the content of antibacterial substances. The white- ripe fruits had significantly higher initial contents of total phenols (7.63 mg · g- 1 ), flavonoids (5.95 mg · g-1 ), and vitamin C (286.59 mg · 100 g-1 ), which might be related to the active synthesis of phenolic substances in the early stage of maturity. The sugar composition in jujube fruits varies with ripeness. In fruits at white- ripe stage, fructose and glucose accounted for a larger proportion, while in the half- red and full- red fruits, sucrose was the dominant sugar component. The total sugar content in the white-ripe fruits showed increased first and then decreased; in the half-red fruits total sugar presented a trend of increasing first, then decreasing and increasing again; and in the full-red fruits displayed a gradual increasing trend. The order of total sugar content among different stages was full- red stage ＞ half-red stage ＞white-ripe stage. Specifically, the total sugar content in the white-ripe fruits reached the maximum on the 3th day (233.04 mg·g-1 ). In the half-red fruits, it increased significantly to 362.78 mg·g-1 on the 9th day. In the full-red fruits, the total sugar content rose significantly to 403.65 mg · g- 1 on the 8th day. The major acids in the fruit included citric acid, tartaric acid and malic acid. During storage, the acid content in the full-red fruits showed constantly increased, and was generally higher than that in the white-ripe and half-red fruits.【Conclusions】This study systematically reveals the postharvest quality changes in“Tayou 12”jujube at maturity stages during storage. The half-red fruits proved to be optimal for harvest, balancing nutrient retention (high antioxidants, balanced sugars), acceptable firmness (6.78 N at day 9), and moderate decay resistance (23.33% decay at day 9). White-ripe fruits are suitable for long-distance transportation or long-term storage; however, their low sugar content and rapid loss of nutrients restrict the fresh-eating quality. Full-red stage is ideal for immediate consumption or processing but requires strict logistics due to poor storage performance. These findings provide a scientific framework for precision harvesting tailored to end- use purposes. Future research should explore controlled atmosphere storage technologies to extend the shelf life of fruit at half-red stage, so as to maximize commercial benefits and consumer satisfaction.