Effects of Astragalus polysaccharides on the heat-induced gel properties and structural changes of myofibrillar proteins in low-salt concentration and its application in luncheon meat.

Abstract

This study investigated how varying levels (0-2.5%, w/w) of Astragalus polysaccharides (AP) influenced the properties of low-salt (0.3 M NaCl) myofibrillar protein (MP) gels and their application in luncheon meat. The highest gel strength and water-holding capacity were observed at a 2% addition level, reaching 89.94 g and 70.25%, respectively, followed by a slight decline at 2.5%. AP enhanced immobilized water retention and G', reduced water channel development, and promoted the development of an ordered protein structure. Compared to pure MP, AP significantly (P < 0.05) increased the turbidity and particle size of the solution, while simultaneously reducing the solubility and the absolute value of the zeta potential, indicating the formation of larger protein aggregates and enhanced protein-protein interactions. SDS-PAGE analysis validated this observation, showing reduced intensities of myosin heavy chain (MHC) and actin bands after AP treatment, with higher molecular weight polymers above the gel. Tertiary structure analysis indicated that AP gradually unfolded MP, with the exposure of sulfhydryl and hydrophobic groups promoting disulfide bonds and hydrophobic interactions cross-linking. Changes in secondary structure were reflected by the shift from α-helix to β-sheet conformation. In luncheon meat, AP improves physical properties such as hardness, springiness, and cohesiveness while reducing cooking loss. Scanning electron microscopy revealed that the surface of luncheon meat tended to be smoother as AP levels increased. In conclusion, the gelling capabilities of MP gel were improved by AP, and the novel quality enhancement for low-salt meat product processing was provided either.