Abstract
Glassy state is thermodynamically non-equilibrium state, and thus the various properties of glassy foods are affected more or less by thermal history such as manufacturing process and subsequent storage. Although the effect of isothermal storage on the non-equilibrium state of glassy foods has been evaluated through enthalpy relaxation measurement by using differential scanning calorimetry (DSC), there is no analytical approach for non-equilibrium state affected by its manufacturing process. To overcome this problem, the previous enthalpy relaxation measurement was extended theoretically, and an analytical approach to evaluate effect of manufacturing process on the non-equilibrium state of glassy materials was proposed. The approach involves that the value of relaxed enthalpy reflecting the thermal history of glassy materials can be evaluated from the difference between first-scanned DSC thermogram and second-scanned one. In addition, this approach was employed for freeze-dried trehalose powder, and the utility of the proposed approach was demonstrated.
