Sorption properties, glass transition and state diagrams for pumpkin powders containing maltodextrins

The state diagrams of freeze-dried pumpkin powders with different maltodextrin additions were developed using glass transition line, freezing curve and maximal-freeze-concentrations conditions. The freezing curve was plotted employing Clausius – Clapeyron equation and glass transition lines were developed using Gordon – Taylor model. The ultimate maximum-freeze-concentration conditions of the powders were observed in range from 0.685 to 0.745 g solids/g sample. Characteristic glass transition temperature of maximum-freeze-concentration (Tg’) of the pumpkin was equal to - 83.7 °C and was increase with increasing maltodextrin addition. Adsorption isotherms of pumpkin – maltodextrin powders were determined at 25 °C by static - gravimetric method and the experimental data was modelled with BET and GAB equations. Monolayer moisture content of the pumpkin powder decreased with increasing maltodextrin additions. The state diagram and water adsorption isotherms of the pumpkin – maltodextrin powders are useful for predicting suitable storage and processing conditions.