Dissecting the Roles of Muscle and Bone Matrix in the Quality and Flavor Profiles of Liquid-Fermented Large Yellow Croaker By-Products

To valorize actual industrial by-products and elucidate how specific substrate components shape fermentation outcomes, this study utilized the meat-on-bone frame (MB) of large yellow croaker (Larimichthys crocea) as the core substrate, using pure muscle (M) and bone (B) as controls to dissect the roles of muscle-derived and bone-derived fractions. The three groups underwent liquid-state co-fermentation with Hongqu lees. Physicochemical, fatty acid, taste, and volatile profiles were monitored throughout a 6-day fermentation. In the initial substrates, with increasing bone proportion, crude protein, fat, and long-chain n-3 polyunsaturated fatty acids (EPA and DHA) decreased, while ash, glycine, and bone marrow-derived monounsaturated fatty acids (MUFAs) increased. During fermentation, accumulation of total acids, amino acid nitrogen, and umami amino acids followed the order M > MB > B. The M group showed the strongest umami, while MB retained abundant unsaturated fatty acids and exhibited closely similar volatile flavor profiles to M. While fermentation time drove the overall progression of flavor evolution, the initial substrate composition was the primary factor determining the final characteristic flavor profiles. Ultimately, MB proved to be a feasible and cost-effective substrate for transforming low-value fish processing residuals into high-quality fermented seasonings with a moderate quality trade-off.