Powdered preparations of fat are the most commonly spray-dried emulsions of the oil-in-water type. Effective spray drying of emulsions stabilised by milk proteins consists in the formation of a solid matrix which guarantees the lowest share of free fat. Such an effective wall matrix is the amorphous structure of sugars. A glassy matrix well protects fat from oxygen and allows for easy reconstitution of the powder in water, but it determines high hygroscopicity and susceptibility of material to caking, which is associated with deterioration in quality, lower solubility and loss of fluidity. The aim of this study was to assay the hygroscopicity and susceptibility to caking of spray dried emulsions containing 5% of sodium caseinate or whey protein isolate, 59 and 39% of maltodextrin and trehalose, and 35 and 55% of rapeseed oil, respectively. The amount of adsorbed water, water activity and the level of caking were determined after 1 and 2 days of storage of powders in an environment with  relative humidity of 43.9% and 64.8%. Water activity in the range of 0.37-0.4 determined the caking of the powders, observed on the second day of storage at relative humidity of 43.9%, and on the first day at humidity of 64.8%, for both the powdered emulsion with the addition of trehalose and in emulsions with the addition of maltodextrin. Powdered emulsions containing trehalose showed higher levels of adsorbed water and higher water activity in comparison with the emulsions with meltodextrin in their composition, regardless of the storage conditions.