A study on gelation of soybean globulin solutions. Part 4. Effect of gelation conditions on the visco-elastic properties and structure of thermotropic gels of soybean globulin fraction.
To the study of the structure and properties of the thermotropic soybean globulin fraction (SGF) gels the stress relaxation and electron microscopy techniques has been applied. The value of slope of normalized relaxation function was used as a characteristic of relaxation properties of SGF gels. This value characterizes the velocity of the gels relaxation processes. It has been found that this characteristic is determined only by the gels' heating temperatures. Using the differential scanning microcalorimetric technique it was shown that the changes of the slope of normalized relaxation function of SGF gels are controlled only by heating temperature. The reason for this lies in the changes of the composition of the denaturation product of SGF gels. The increase is shown of the shear moduli of gels prepared at other than optimum temperatures by additional heating under optimal gelation conditions. That is a result of existence of a sol-fraction. The most significant increase of shear moduli is found for the SGF gels, sol-fraction of which is native 11S globulin. A correlation has been established between the changes of SGF gels' structure obtained from the dates of rheological measurements and electron microscopy technique.