Effect of carbohydrate type on the DVS isotherm-induced phase transitions in spray-dried fat-filled pea protein-based powders

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 (aw) within the range of 0.005-0.95 and at 25, 30 and 35 °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 polydextrose in the range of aw 0.3-0.7 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.