State diagram of freeze-dried garlic powder by differential scanning calorimetry and cooling curve methods

The state diagram of freeze-dried garlic powder was developed using freezing curve, glass transition line, and maximal-freeze-concentration condition. Freezing points of garlic powder were measured by differential scanning calorimetry (DSC) and the cooling curve method, whereas glass transitions were measured by DSC. The freezing curve and glass transition line were modeled using the Clausius-Clapeyron equation, adjusted with unfreezable water, and the Gordon-Taylor model, respectively. Maximal-freeze-concentrated condition was found as X_w′ (characteristic water content) = 0.82 [X_s′ (characteristic solids content) = 0.18] with the characteristic temperature of glass formation being T_g′ (characteristic glass transition) = -38.6°C and T_m′ (characteristic end point of freezing) = -26.0°C. Other characteristic glass transitions T_g″ and T_g‴ equal to -29.3°C and -48.6°C, respectively.