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Dry processing is ineffective in preserving fresh jujubes (Zizyphus jujuba Mill.), contributing largely to the delayed jujube harvest in Xinjiang. However, no studies have evaluated the impact of delayed harvest periods on processing quality. Therefore, the present study investigated the effects of different delayed harvest periods on the characteristics of the quality of jujubes in Xinjiang after hot air drying. Six batches (S1–S6) were sampled over a 7-d period. Various indicators of jujubes changed significantly during the extended harvest period (P < 0.05). The water content of the fruit decreased progressively. While the percentages of soluble solids, total sugars, and reducing sugars increased continuously, the total weight of these parameters in a single jujube fruit decreased continuously. The proportion of ascorbic acid, total weight, and drying time decreased steadily. The fruit had the highest ascorbic acid content at the S4 stage after hot air drying (87.14 mg 100 g−1). Fewer color differences were recorded in hot air-dried fruits as compared with fresh jujubes; the cracking rate decreased after hot air drying, but the fruit could be rehydrated more effectively. A comprehensive evaluation revealed that jujubes harvested in the S4 stage were better suited for dry processing. [ABSTRACT FROM AUTHOR]

Jujube is a crop highly resistant to drought and salinity, making it one of the main fruit trees in Xinjiang. The present study evaluated the changes in the physicochemical and antioxidant activities of jujube fruit of eight different cultivars from Xinjiang, China. The developmental stages were selected according to the days after full bloom and fruit peel colour during ripening; these stages included young (S1), fruit core-hardening (S2), green ripening (S3), half-red maturity (S4) and complete red. In present study, different cultivars of jujube fruit showed similar chemical profiles, but their amounts showed great variation. HZ had the highest content of sugars, and JY had the highest content of cAMP and cGMP, while relatively higher levels of ascorbic acid, catechin, epicatechin, rutin, proanthocyanidin and antioxidant activity were found in 'FS' than in other cultivars, indicating that 'FS' could be used as a potential natural antioxidant. Regarding the development stages of jujube fruit, the moisture, ascorbic acid, total polyphenol, catechin, epicatechin, proanthocyanidin and rutin contents decreased during the development of all jujube cultivars, while the fructose, glucose, sucrose, cAMP, and cGMP contents greatly increased. The antioxidant activity determined by DPPH and ABTS radical scavenging decreased as the fruits matured. Therefore, the results suggest that green jujube (S1) could be used for natural antioxidants (catechin, epicatechin, proanthocyanidin) and that the advanced ripening stage(S5) is the proper picking period for fresh fruit and commercial processing. [ABSTRACT FROM AUTHOR]