MEASUREMENT OF TEMPERATURE-DEPENDENT ICE FRACTION IN FROZEN FOODS

Ice fraction was measured for solutions containing glucose, sucrose, gelatin, and egg albumin at various concentrations at temperatures from 0 to -20-degrees-C. For glucose and sucrose solutions, the ice fraction was accurately measured from phase diagram, which could be interpreted by solution thermodynamics with two parameters. The ice fractions of these sample solutions increased with decreases in both temperature and concentration. Because of the limited applicability of the phase diagram method only to systems with low molecular weight materials, the DSC method was also used for ice fraction measurement. The DSC method, corrected for temperature-dependent latent heat of ice and corrected with Pham's equation, provided a good approximation for ice fractions with general applicability. The DSC method was used to measure the ice fractions of gelatin and egg albumin gels as a function of solute concentration. The freezing point and bound water of gelatin and egg albumin gels were described as a function of concentration. Effects of the differences in molecular structure on ice fraction were analyzed for various carbohydrate solutions at the same concentration. The ice fraction proved to be strongly dependent on the colligative properties of the solution with nonideal behavior.