Microbial proteolysis and glycolysis coordinate gel structure, water mobility and antioxidant potential in cooked fermented meat-pea protein hybrid sausages.

This study investigated the effects of partial meat replacement (0%, 25%, and 50%) with plant-derived components (pea protein isolate and pea flour) on proteolysis, protein network structure, and water mobility in reduced-salt (0.3 M NaCl) cooked fermented hybrid sausages. Fermentation with a mixed culture of Lactobacillus sakei and Staphylococcus carnosus resulted in pH reduction to 4.5-4.6 and titratable acidity increases to 2.04-2.33%, establishing an acidic matrix governing hybrid protein reorganization. Fermented sausages showed a reduced extractable protein content (P < 0.05), increased free amine groups (P < 0.05), and pronounced changes of polypeptide profiles, indicating concurrent occurrences of protein network formation and peptide-level hydrolysis. Total free amino acids content rose markedly in pea-substituted sausages after fermentation (from 2.6 to 2.7 to 4.2-5.5 mg/g, P < 0.05), whereas only minor changes occurred in all-meat control. These proteolytic changes corresponded to significantly elevated radical-scavenging (ABTS) and Trolox-equivalent antioxidant capacity (up to 1.3 and 1.5-fold, respectively), most notably for pea-containing formulations. Fermentation strengthened the sausage matrix, as evidenced by increased hardness and breaking force (P < 0.05), and pea substitution modulated the specific rigidity and deformability. Meanwhile, pea substitution reduced cooking loss and shifted retained water toward more tightly bound states within a more homogeneous spatial distribution, as supported by 1H-LF-NMR and MRI, consistent with microstructural observations. These findings elucidate the coupling roles of fermentation-induced acidic gelation and proteolysis in regulating protein network organization, water mobility, and functional performance, supporting the development of sustainable reduced-salt cooked fermented hybrid meat products.