Combined non-volatile and volatile metabolite profiles and antioxidant activities reveal the enhancement of traditional "steaming and Sun-drying nine times" on the functional properties of jujube.

Jujube is recognized as a health food, particularly following the traditional "Steaming and Sun-Drying Nine Times" treatment. This study aimed to clarify the scientific rationale of this practice by systematically analyzing changes in metabolite profiles and antioxidant activities. The results demonstrated that repeated steaming and sun-drying significantly increased the levels of phenols, flavonoids and antioxidants in jujube. To comprehensively assess the dynamic changes in metabolites during processing, UPLC-QE-Orbitrap MS and HS-GC-Orbitrap MS were performed to determine the non-volatile and volatile metabolites, respectively. A total of 428 non-volatile and 36 volatile metabolites were identified, revealing substantial compositional differences induced by the treatment. KEGG pathway analysis indicated that the affected metabolites were primarily involved in amino acid and lipid metabolism. Furthermore, correlation analysis demonstrated significant associations between differential metabolites and antioxidant activities. These findings offer comprehensive insights into the biochemical mechanisms underlying the enhancement of jujube quality through traditional steaming and sun-drying.