Effect of polydextrose and NaCl on the initial freezing point of chicken, egg and surimi

Initial freezing points (T 1 ) of chicken, egg (mixture of egg yolk and white, egg yolk, egg white) and surimi mixed with different mass fractions of polydextrose (w= 1-10%] and NaCl (w = 1-10%) were determined by using differential thermal analysis (DTA). Relationships between the decrease of T as a function of mass fractions (w) of the added substances were determined by linear regression analysis. The greatest effect on freezing point depression was exhibited by egg yolk mixed with NaCl (from -0.59° to -18.77°C), and the least effect was exhibited by egg mixture with polydextrose (from -0.40° to -0.49°C). Two multivariable regression models based on mass fractions of protein and fat content and the added substances predicted T with coefficients of determination (R 2 of 0.96 and 0.98. There were differences in the T 1 values for samples of chicken, surimi, egg yolk, egg white, egg mixture and water solution of polydextrose, as a function of the mass fraction of polydextrose calculated on the total mass of water. These findings support the assumption that polydextrose interacts with proteins in egg, chicken and surimi, resulting in an increase in the mass fraction of bound water, which depresses T 1 . The negligible interaction of NaCl and protein can be explained by the same argument. The results are compared and discussed with the Pham model for prediction of T.