MEASUREMENT OF TEMPERATURE-DEPENDENT ICE FRACTION IN FROZEN FOODS

Ice fraction was measured for solutions containing glucose, sucrose, g elatin, and egg albumin at various concentrations at temperatures from 0 to -20-degrees-C. For glucose and sucrose solutions, the ice fracti on was accurately measured from phase diagram, which could be interpre ted 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, th e DSC method was also used for ice fraction measurement. The DSC metho d, corrected for temperature-dependent latent heat of ice and correcte d with Pham's equation, provided a good approximation for ice fraction s with general applicability. The DSC method was used to measure the i ce fractions of gelatin and egg albumin gels as a function of solute c oncentration. The freezing point and bound water of gelatin and egg al bumin gels were described as a function of concentration. Effects of t he differences in molecular structure on ice fraction were analyzed fo r various carbohydrate solutions at the same concentration. The ice fr action proved to be strongly dependent on the colligative properties o f the solution with nonideal behavior.