Freeze-drying resulted in a highly porous product with small pores, which sorbed more water than the other dried materials. Sorption isotherms of freeze dried food powders and model systems had been investigated by several research workers: instant tea, dairy powders; pineapple pulp powder garlic powder and model fruit powders studied desorption isotherm of
milk powders at elevated temperatures and over a wide range of relative humidity using a dynamic method and generated results that can be used in spray drying simulations or spray drier designs for dairy powder production.