Water and Molecular Weight Effects on Glass Transitions in Amorphous Carbohydrates and Carbohydrate Solutions

The effects of water, freeze-concentration and effective molecular weight (M_e) on glass transition (T_g) of maltose and maltodextrins were studied, and methods to predict T_g were used to establish state diagrams. T_g of maximally freeze-concentrated solutes (T′_g) and onset of ice melting (T′_m) increased with M_e, and for high molecular weight polysaccharides T′_g and T′_m were predicted to have the same temperature value. Ice formation at T′_gm was time dependent. Unfrozen water in maximally freeze-concentrated matrices was about 20% independently of M_e. The state diagrams can be used to evaluate physical state of frozen and dehydrated foods.