Quality Improvement of Porcine Bone Broth via Enzyme-Driven Flavor Release and Structural Modification

In this study, post-simmering enzymatic hydrolysis was employed to improve the quality of porcine bone broth by physical structure and rheology modulation. The effect of papain, lipase, and synergistic dual-enzyme hydrolysis on sensory quality and flavor profiling were compared. Results showed that papain-treated broth (PA) exhibited superior sensory characteristics of smoothness, richness, umami, sweetness, and characteristic aroma than samples treated with lipase (PR) or a combination of papain and lipase (AR). Taste-active compound analysis revealed more umami and sweet amino acids, 5'-nucleotides, and succinic acid in PA, yielding an equivalent umami concentration (EUC) of 10.68 g monosodium glutamate (MSG)/100 g. A potent taste base was formed as papain-hydrolyzed proteins into key taste compounds (amino acids, peptides) while releasing succinic acid and 5'-nucleotides. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that PA exhibited a higher concentration of aldehyde with fatty, sweet, fruity, and floral aromas as well as characteristic volatiles (1-octen-3-ol, 2-pentylfuran, and 2,5-dimethylpyrazine) with strong mushroom, fatty, and grilled meat aroma. Physical characterization demonstrated that enzymatically derived emulsifying proteins and peptides established a stable emulsion system with finer particle size, favorable viscosity, and shear force. This not only imparted richness and smoothness to the broth but also promoted the long-lasting release of key volatile components by shortening the diffusion path of lipid-soluble aroma compounds to the oil-water interface. Partial least squares regression analysis further confirmed the critical role of particle size, viscosity, sugar, and amino acids on the sensory quality of porcine bone broth. This study provided a feasible enzymatic strategy and clarified processing-structure-flavor correlations for industrial production.