Effects Of Different Treatments On Gel Properties Of Mixture Of Myofibrillar Protein And Soy Protein Isolate

Soy protein isolate (SPI) is an inexpensive, yet, nutritious and functional food ingredient. It has been a common functional ingredient in processed meats for many years. However, the final temperature of processed meats could not sufficient to denature the main components of soy protein (7S and 11S), thereby limiting its interaction with muscle proteins. In order to enhance its functionality in meats, we adopted different treatments (thermally modified soy protein, pressure pretreatment mixed proteins) to study the gels properties of mixed proteins, and then get better parameter of mixed gels.Three main parts were involved in this paper: Firstly, we have to choose the best condition for chicken MPI gels(pH, NaCl concentration and MPI concentration ). The orthogonal test L9(3⁴) was used to seek the effects of pH, concentration of NaCl, concentration of MPI on gel texture property (hardnesss, springiness and water holding capacity). Results indicated, for MPI gel, concentration of NaCl was the most obvious effect on hardness and springiness, followed by concentration of proteins, and the effect of pH on hardness and springiness was smallest. While Concentration of NaCl was the most obvious effect on WHC, followed by pH, and the effect of concentration of proteins on WHC was the smallest. Comprehensively considering, pH 6.0, NaCl 0.6 M, concentration of proteins 20 mg·mL^-1 is the optimal combination for heat-induced gelation of MPI.Secondly, effects of modified SPI by the methods of heating on gel of mixed proteins (MPI/SPI) were mainly investigated, and then the optimal concentration of Ca²⁺, Mg²⁺ for gel of modified SPI and MPI were studied. The modified condition is heating at 90℃for 4min. Results indicated, in the processing of gel, modified soybean protein improved gelation properties, promoted the interaction with MPI, and CaCl₂ (0.01 M) could improve the hardness of gel of MPI and S90, and MgCl₂(0.01 M) could improve gel springiness, WHC, however, high concentration of divalent ion possessed negative effect.At last, the heat-induced gelation of mixed MPI and SPI pretreated with high pressure were investigated. The mixed proteins of 100 MPa had better dynamic rheological behavior than unpressurized proteins. SDS-PAGE patterns indicated that no modification of primary structure of single proteins by high pressure, but have changes in the mixed system. When mixed pressurized proteins was heated at 55℃for 20min, the structures and characteristics of gels were better than the traditional heat-induced gels. The results suggest that high pressure is potentially useful for improvement in the gel-forming ability of mixed proteins, but the higher pressure was not good for that.