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 in vitro 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 (p < 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%, p < 0.05), with corresponding the highest hardness and cohesiveness values of 102.47 N and 0.44, respectively, among the treatments (p < 0.05). In vitro 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, p < 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, p < 0.05), whereas NaCl 1.5% had the lowest value (1.96 mM/g, p < 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 in vitro protein digestive behaviors.