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(g)' < T < T(m)' 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.