Effects of Low-Sodium Salt Mixture Combined with L-Lysine or L-Arginine on the Structure and Gel Properties of Myofibrillar Protein

This study investigated the effects of a low-sodium salt mixture (0.4 mmol/L, concentration ratio of NaCl to KCl = 2:1) added with L-lysine (L-Lys) or L-arginine (L-Arg) at concentrations of 1, 3, and 5 mmol/L on the structure and gel properties of myofibrillar protein (MP) using the salt mixture added with 1 mmol/L pyrophosphate (PP) as the control. The results indicated that compared with conventional salt treatment (0.4 mol/L NaCl + 1 mmol/L PP), the low-sodium salt + PP treatment slightly but not significantly improved the water-holding capacity, texture, and rheology of MP gels. Compared with its combination with PP, the low-sodium salt mixture combined with basic amino acids (L-Lys and L-Arg) promoted the transformation of α-helix into other secondary structures and induced alterations in the surface properties of MP. Furthermore, the addition of L-Arg significantly reduced the average particle size and increased the solubility of MP. The addition of 5 mmol/L L-Arg decreased the average particle size by 22.1% and elevated the solubility by 330.9% (P < 0.05). The incorporation of basic amino acids enhanced the storage modulus (G′), reduced the cooking loss, and improved the water-holding capacity of MP gels. Low-field nuclear magnetic resonance (LF-NMR) analysis revealed that the addition of basic amino acids resulted in an overall shortening of the relaxation time of immobilized water in MP gels, which signifies a reduction in the mobility of water molecules within the gel matrix. Scanning electron microscopy (SEM) showed that the addition of basic amino acids promoted the formation of a more fine, uniform and compact microstructure during the heatinduced gelation of MP. In conclusion, basic amino acids (especially L-Arg) can significantly improve the solubility and gel properties of MP under the condition of “low sodium and no phosphorus”, which provides a theoretical basis and reference for the development of healthy meat products.