EFFECT OF SUCROSE CONTENT ON THE MOISTURE SORPTION ISOTHERMS OF OSMODEHYDRATED APPLES AT VARIOUS TEMPERATURE

Desorption isotherms of apples after dehydration-impregnation by soaki ng (DIS) were determined at 20, 40, 60 and 80-degrees-C. The experimen tal procedure was a gravimetric static method. The data were fitted wi th GAB and BET models. Sucrose impregnation decreases the thermal suce ptibility of apple sorption capacity. At 60-degrees-C, isotherms are i dentical. At 80-degrees-C, sucrose impregnation depresses water activi ty, while at 20 and 40-degrees-C the opposite effect is observed. Evol ution of moisture content at the first saturation layer expresses thes e effects of sucrose impregnation and temperature. Interpretation is b ased on the prominent forms of sugars (cristalline-amorphous) at moist ure equilibrium or pseudo-equilibrium. Two main consequences appear wh en drying osmodehydrated apples: the aw depressing effect increases th e final weight of the product and decreases its apparent drying time.