Texture, microstructure, and in vitro digestion of hybrid meat gel-type sausages formulated with functionalized pea protein

This study investigated the effects of complex formulations on the textural and microstructural properties of prototype reduced-salt (0.3 M NaCl as opposed to regular 0.6 M NaCl) hybrid meat sausages and compared the in vitro digestion behavior and oxidation stability. Plant-based ingredients, including functionalized (ultrasound) pea protein isolate and pea flour, were incorporated to substitute lean meat at three levels (ratios 100:0, 75:25, and 50:50 w/w). Cooked hybrid emulsion sausages (4.5 % canola oil) exhibited a slightly pink cured color, but the chromatic a∗ value decreased 16–39 % with pea protein substitution. Hardness and breaking force declined with increasing substitution levels, whereas deformability displayed an upward trend. In contrast to regular-salt (0.6 M) sausage, where pea protein substitution decreased texture uniformity, the substitution in reduced-salt (0.3 M) hybrid sausages resulted in a denser protein network. In corroboration, reduced-salt sausage with pea protein substitution demonstrated restricted bulk water mobility, as evidenced by ¹H NMR, leading to significantly less cooking loss (28–31 %, P < 0.05) compared with non-substitution control. During simulated in vitro digestion (1 h pepsin followed by 2 h trypsin), approximately 90–95 % protein in hybrid sausages was hydrolyzed into short peptides and amino acids, leaving a small fraction of oligopeptide remnants (<17 kDa). Nevertheless, hybrid sausages were susceptible to lipid oxidation, with TBARS rising to 2.0–2.7 mg malonaldehyde/kg from all-meat control (0.24 mg/kg), underscoring the necessity for antioxidant protection. These findings contribute to the knowledge base for the development of sustainable hybrid meat alternatives.