Assessment of sugar content, fatty acids, free amino acids, and volatile profiles in jujube fruits at different ripening stages.

Volatile profiles of jujube fruits at different ripening stages were characterized by GC-MS and E-nose. Changes in the possible precursors of volatile components were also investigated. Four ripening stages were established: GM, green maturity; YM, yellow maturity; HRM, half-red maturity; RM, red maturity. Fruit maturity showed significant effect on the volatile components and their precursors. (E)-2-hexenal was the most abundant component which showed rising trend from 169.2 μg/kg (GM) to 733.4 μg/kg (RM). Glucose and fructose showed a decreasing tendency during ripening. As the important precursors of jujube flavor, seven fatty acids were identified, the predominant ones were C16:0, C16:1n7, C18:1n9c and C18:2n6c; twenty-six free amino acids were quantified, in which l-AspNH2 and l-Pro were the abundant components. Owing to the highest content of total aldehydes (59.33%) and the strongest responses of E-nose, jujubes at HRM stage showed superior overall flavor quality among all the samples.