Effect of Konjac Gum on the Gel Structure and Rheological Properties of Myofibrillar Protein-Soy Protein Isolate Composite

To develop low-salt meat products and achieve the reduction in costs of meat production, the effect of konjac gum on the gel properties of soy protein isolate (SPI)-myofibrillar protein (MP) composite at various salt concentrations was investigated in this study. For the purpose of evaluating the effects of SPI, konjac gum, salt concentration, and other factors on MP gel formation, rheological properties and microstructures of the SPI-MP composite gels were analyzed using a rheometer and scanning electron microscopy. The obtained results indicated that at low salt concentration (0.3 mol/L NaCl), the gel strength of 3% MP-1% SPI composite gel significantly increased (P<0.05) to 97 g relative to 43 g of the 4% MP gel, and the water-holding capacity also increased from 36% to 50%. However, the gel strength and water-holding capacity were decreased when the replacement amount of SPI increased (2% MP-2% SPI composite) compared with 3% MP-1% SPI composite. The gel strength decreased from 177 g of 4% MP to 89 g of 2% MP-2% SPI composite with at 0.6 mol/L NaCl concentration. The gel strength and water holding capacity of the MP-SPI composite gel were increased after adding high amount of konjac gum. At 0.3 mol/L NaCl concentration, the gel strength of 2% MP-2% SPI composite increased from 66 g to 93 g after adding 1% konjac gum, and the water holding capacity also increased from 44% to 65%. Therefore, konjac gum can eliminate the disruption of SPI on the gel formation of MP. The results of scanning electron microscopy revealed that the strong water-holding capacity of konjac gum and the filling effect of SPI led to the increase in gel strength. Consequently, at the concentration of 0.3 mol/L salt, 0.5%~1% konjac gum could improve the characteristics of MP protein gel with low SPI substitution (1%).