Rheological properties and physical stability of o/w emulsions stabilized by OSA starch with trehalose

This study investigated the effect of oil content (10, 16 and 22% of rapeseed oil) and OSA starch content (4, 8 and 12%) as well as homogenization pressure (60/15, 36/12 and 12/4 MPa) on rheological properties, droplet size distributions and stability of o/w emulsions with the addition of trehalose. The composition of emulsions corresponded to that of the systems subjected to spray-drying during production of microencapsulated lipid powders. The majority of the prepared emulsions were shear-thinning non-Newtonian fluids. The factors that determined their rheological properties to the greatest extent were the content of oil phase and concentration of OSA starch which contributed to increased viscosity of emulsions and shear thinning effect. Pressure variants: 60/20 MPa and 36/12 MPa applied in two-stage homogenization enabled achieving satisfactorily small sizes of fat globules (<10 μm) that ensured physical stability of emulsions, especially at the highest applied concentration of OSA starch (12%), regardless of the oil content. Destabilizing processes of creaming occurred in the systems produced upon pressure homogenization at 12/4 MPa. Homogeneity of all emulsions in terms of droplet size distribution did not change significantly during 6 days of storage, and thus there was no coalescence of oil droplets. There were also no changes in the rheological properties of the emulsions during storage.