Exploring the in vitro protein digestive behaviors of pork sausage models based on NaCl level-dependent gel properties

This study investigated the impact of varying NaCl concentrations on the gel properties and <i>in vitro</i> digestive behavior of pork sausage models. Meat batters formulated with pork shoulders were prepared with NaCl concentrations of 1.0% , 1.5%, and 2.0% (w/w). NaCl 2.0% yielded the lowest actomyosin content (33.46%) and highest total protein solubility (0.61 g/g) in the batter (<i>p</i> < 0.05), followed by 1.5% (34.72% and 0.56 g/g, respectively) and 1.0% (42.19% and 0.55 g/g, respectively). Subsequently, pork sausage models were produced by placing the batters in stainless-steel cans, vacuum-packing, and heating. The sausages prepared with NaCl 2.0% exhibited the lowest cooking loss (2.8%, <i>p</i> < 0.05), with corresponding the highest hardness and cohesiveness values of 102.47 N and 0.44, respectively, among the treatments (<i>p</i> < 0.05). <i>In vitro</i> gastric digestion revealed that lower NaCl concentrations (1.0% and 1.5%) led to a higher release of α-amino groups (0.29 and 0.31 mM/g, respectively) than NaCl 2.0% (0.24 mM/g, <i>p</i> < 0.05) with the larger and more aggregated gel particles in the fluorescence microscopic images. However, after the small intestinal digestion, NaCl 1.0% retained the highest release of α-amino groups (2.19 mM/g, <i>p</i> < 0.05), whereas NaCl 1.5% had the lowest value (1.96 mM/g, <i>p</i> < 0.05). These findings illustrate that the variations in the physicochemical and gel properties of pork sausages depending on the NaCl levels result in the different <i>in vitro</i> protein digestive behaviors.