Integrated untargeted metabolomics and lipidomics to reveal molecular mechanisms underlying flavor development in hot-air-dried oysters.

During the drying process of oysters, volatile flavor compounds such as aldehydes, ketones, alcohols, and esters are produced. Previous studies have shown that lipids are important precursors of these volatile flavor compounds. However, the mechanism of flavor formation in dried oysters remains unclear. This study aims to investigate the changes and potential relationships between volatile flavor substances and their precursors during hot-air drying (HAD) of oysters (at 0, 4, 8, and 12 days). Using GC-MS and UPLC-MS/MS, 68 volatile flavor compounds, 842 lipid components, and 641 metabolites were identified. The results revealed that the content of volatile flavor substances increased with drying time, primarily forming in the later stages of drying. Mechanistically, lipid oxidation-induced fatty aldehydes constitute the main structural components of volatile flavor compounds in dried oysters. KEGG analysis indicated that the primary metabolic pathways during oyster drying were amino acid metabolism and biosynthesis. Lipid oxidation supplies precursor molecules that form the basic flavor framework, such as aldehydes and ketones; the Maillard reaction constructs heterocyclic backbones, thereby imparting characteristic heterocyclic aromas; and amino acid metabolism fills in three-dimensional cascades containing sulfur or nitrogen groups. These processes contribute to the formation of the complex flavor network in dried oysters.