Water adsorption isotherms of texturized soy protein

Texturized soy proteins (TSP) have been used for many years as a substitute of animal protein. In recent times, TSP was used as a functional ingredient in several food applications; its process involves a drying step. The water adsorption isotherms of TSP were determined using the static method of saturated salt solutions at 10, 20, 30 and 40 °C. The experimental data were fitted to Oswin, Halsey, BET, GAB, Peleg and Darcy Watt models. The equilibrium moisture content at water activities up to 0.9 decreased as the temperature was increased from 20 to 40 °C. At higher water activities, the moisture content showed an inverse behavior, resulting a crossover of the isotherms. The GAB and Peleg equation showed the best fit for the experimental curves. The total heat of sorption of TSP increased with decreased moisture content.