The objectives of research were to investigate the moisture sorption behavior of twelve spray-dried fat powders using dynamic vapor sorption (DVS) adsorption isotherms at twenty-three values of water activity (a(w)) within the range of 0.005-0.95 and at 25, 30 and 35 degrees C. The model fat powders were formulated with high vegetable oil content (solid below 28-30 palm/rape blend oils, or rape oil), and a constant carbohydrate-to-protein-component ratio. The DVS isotherms showed good consistency in determination of the moisture-induced phase transitions of amorphous carbohydrate components in fat powders. Powders made with Nutriose demonstrated a constant moisture adsorption rate up to the aw value of -0.7, without phase transition upon humidification. Powders with trehalose, inulin and poly dextrose in the range of aw 03-0.7 went through a glass transition and most likely crystallized. It seemed that with more solid fat in powders, there was higher water activity and moisture content to induce phase transitions. (C) 2017 Elsevier Ltd. All rights reserved.