WATER ACTIVITY and PHYSICAL STATE EFFECTS ON AMORPHOUS FOOD STABILITY

Abstract

Water-adsorption data and glass transition temperatures (Tg) of maltodextrins with dextrose equivalent (DE) values ranging from 4 to 38, horseradish roots, and strawberries were used to establish relationships between water activity (aw), water content (m), and Tg. Critical m values were considered as those depressing Tg to 25C. Corresponding values of critical aw were obtained from GAB isotherms that were used to model water adsorption. the use of BET isotherms was tested, but the model showed poor correlation with experimental data at high aw values, especially for low DE maltodextrins. Critical m and aw values were lowest for strawberries (1.5 g H2O/g solids; 0.07 aw). the values increased with decreasing DE, ranging from 7.2 (0.44 aw) to 11.2 g H2O/g solids (0,70 aw). Understanding of water-sorption properties and Tg is valuable in controlling processability and stability, and for determining of food-packaging requirements.