Glass transition and state diagram for freeze-dried Agaricus bisporus

Sorption isotherms and state diagram of freeze-dried Agaricus bisporus were developed to further investigate the connection between the two distinct criteria of food stability. Sorption isotherms of freeze-dried A. bisporus were determined by the gravimetric method and the data were modeled by GAB model. The GAB monolayer moisture content was calculated to be 6.2 g/100 g (d.b.). The glass transition temperature of freeze-dried A. bisporus was determined by differential scanning calorimetry. The state diagram was composed of the freezing curve and glass transition line. which were fitted according to Clausius-Clapeyron model and Gordon-Taylor model, respectively. The state diagram yielded maximally-freeze-concentrated solutes at 0.704 solids with the characteristic temperature of glass formation being -77.9 degrees C. The state diagram and sorption isotherms of freeze-dried A. bisporus are useful in evaluating the storage stability as a function of temperature and moisture content as well as optimizing drying and freezing conditions. (C) 2012 Elsevier Ltd. All rights reserved.