Reduction of NaCl in oxidized myofi brillar protein by substitution with chloride salts: underlining the gel changes and gastric digestive properties

The changes and gastric digestive properties of gel were investigated for oxidized myofibrillar protein (MP) (0 – 1 mmol/L H₂O₂) treated by 30% substitution of NaCl with KCl, MgCl₂, and KCl/MgCl₂. Mild oxidation level (0.3 mmol/L H₂O₂) facilitated the protein unfolding, and MgCl₂ obviously intervened the protein self-assembly by forming the salt bridge and more disulfide bonds. At the same oxidation concentration, the sodium-reduced MP substituted with KCl formed dense network structure with better gel strength (increased by 6% – 18%) and water retention in comparision to the gel without sodium reduction. The KCl-substituted gel chewing work was also relatively higher among the low-sodium samples at the first chewing cycle. Reversely, the relatively soft structure and lower gel viscosity in simulated oral chewing were found in MgCl₂-substituted gel. These changes decreased the contact limit between pepsin and protein for better gastric disintegration or pepsin diffusivity, and increased the proportion of small molecular weight peptides (25.83%, < 5 kDa). Therefore, partial substitution of NaCl with other salt replacers could influence the physicochemical properties of low-sodium MP suspension or gel under different oxidation degree and the subsequent gastric digestion characteristics.