Enthalpy Changes of Foods in Freezing and Thawing Processes (III)

Enthalpy of solid of foods and hulled rice

Abstract

Using two conduction calorimeters, the authors measured specific heat and enthalpy of solid of several foods and hulled rice in the low temperatures. The following results were obtained.
1) Specific heat of solid of gelatin, market milk and hulled rice increased in direct proportion to temperature increased. The increment which seemed to be caused by melting of fats on specific heat-temperature curve was observed in yolk and bean curd.
2) Average specific heat of solid in many foods was 1.3-1.5 kJ·kg^-1·k^-1 in a range from 273 to 293 K.
3) From the measurements of specific heat of hulled rice, critical water contents of freezing was about 21%wb.
4) Enthalpy-water contents diagram in a range from 0 to 25%wb and from -20 to 20°C was drawn for hulled rice.