FRACTURE-STRESS OF FROZEN FOOD ANALYZED BY A 2-COMPONENT MODEL CONSISTING OF PURE WATER ICE AND CONCENTRATED AMORPHOUS SOLUTION

Fracture stress of soybean curd was measured at temperatures between - 20 degrees C and -196 degrees C by compression tests. Fracture stress increased as the temperature decreased until it reaches a characterist ic temperature; below this temperature the fracture stress was constan t. Fracture stress varied with the moisture content of the sample meas ured before freezing; the lower the moisture content, the higher the f racture stress. We attempted to analyze the fracture stress of the fro zen soybean curd using a mathematical model in which frozen soybean cu rd was regarded as a two-component system consisting of pure water ice and concentrated amorphous solution (CAS). Since the volumetric fract ion of pure water ice in the system is required for the analysis, the degree of freezing of soybean curd with varied moisture content was es timated as a function of temperature using a hypothetical phase diagra m for soybean curd. Based on these data, fracture stress of CAS was ca lculated using a series model and a parallel model. The calculated fra cture stress of CAS was found to be a unique function of temperature a nd independent of moisture content before freezing.