Effect of citrus fiber on the phosphate-mediated gel properties of myofibrillar protein and partial replacement of phosphate

To evaluate the effect of citrus fiber (CF) on the phosphate-mediated gel properties of myofibrillar protein (MP) and partial replacement of phosphate, gels properties, emulsifying properties, molecular forces and structural characteristics, water distributions, microstructure of MP composite gels with sodium tripolyphosphate (STP) and CF were investigated. The results showed that the addition of STP and CF could enhance the gel properties by unfolding the structure of α-helix, and increasing the hydrophobic interactions and hydrogen bonds, which were the primary molecular forces to stabilize the structure of MP-STP-CF composite gels. The measurement of relaxation time and microstructure further verified that STP and CF could convert more free water into immobile water, forming a more stable three-dimensional network structure. MP gel added with 5% STP and 10% CF exhibited the best gel properties, but excessive CF addition would weaken the intermolecular forces and immobile water content, then destroyed the gel properties. Moreover, MP gel with 3% STP and 10% CF addition had no significant difference on the gel properties and structures compared with MP gel with 5% STP. The results provided basic theoretical support for the application of CF in improving the structure of meat products and the partial substitution of phosphate.