Elucidating the interplay between lipases and lipid metabolites during the processing of dry-cured Wuchang fish (Megalobrama amblycephala)

This study systematically investigated lipid metabolic alterations during the dry-curing processing of Wuchang fish (Megalobrama amblycephala) using ultra-performance liquid chromatography-tandem mass spectrometry coupled with an in-house lipidomics database. A total of 1 370 lipid species were identified, classified into six major categories (fatty acids, glycerolipids (GL), glycerophospholipids (GP), prenol lipids, sphingolipids, and sterol lipids) and 41 subclasses. Orthogonal partial least squares-discriminant analysis revealed significant lipidomic divergence among three processing stages (fresh fish (CK), curing for 2 days (Y2), and drying for 2 days (G2)), with GL dominating the lipid profile and GP exhibiting marked depletion during salting. The lipid oxidation index elucidated competing effects of lipid hydrolysis (substrate depletion) and oxidation (metabolite generation), revealing that lipoxygenase-driven conversion of polyunsaturated fatty acids (PUFAs) to volatile aldehydes and alcohols predominated during salting, while reduced water activity in air-drying triggered PUFAs autoxidation and oxylipins accumulation. Post-processing nutritional enhancement was evident, with essential fatty acids (eicosapentaenoic acid, docosahexaenoic acid, linoleic acid, and oleic acid) significantly enriched in air-dried fish, constituting 18.869% of total free fatty acids, a substantial increase from 13.414% in fresh samples. This work provides critical insights into flavor formation mechanisms and quality control strategies for traditional dry-cured fish products.