Controlled drying of protein particles to improve oil dispersibility for oleogelation

Protein oleogels are promising substitutes for solid fats, but the mainstream oleogelation methods are indirect and involve multiple steps to bring protein from an aqueous phase into the oil phase. Depending on the method used, it is also difficult to control the specific properties of the oleogels, as the protein content and structure cannot always be controlled. The aim of this research was therefore to create protein powders that can be directly dispersed in oil to create protein oleogels. This requires a well-flowing protein particle powder, which was produced using a drying method with apolar solvents. Solvents with decreasing polarity, such as mixtures of water, isopropanol, and hexane in different ratios, reduced the attractive forces between protein particles upon drying by decreasing the solvent wettability and accompanying capillary forces. Two proteins were included: whey protein isolate (WPI) and potato protein isolate (PoPI), which were directly dispersed in oil by bead milling, resulting in protein oleogels. Stable protein oleogels were only obtained from solvent mixtures with a minimum apolarity, to ensure the protein particles were small enough for proper oleogelation. For WPI, a mixture of 50% (v/v) water and 50% (v/v) isopropanol was sufficient, whereas a more apolar mixture of 25% (v/v) water and 75% (v/v) isopropanol was required for PoPI. Such a low degree of polarity was required to reduce the protein particle size to less than 1 μm, thereby enabling strong network formation. For solvents with higher polarity, protein agglomeration during drying was not prevented, and the large protein agglomerates were not able to create the needed 3D protein network. In conclusion, we showed that particle agglomeration can be prevented by drying from apolar solvent mixtures, which leads to the formation of protein particles that are sufficiently small to be used for a direct-dispersion method for protein oleogelation. This simplifies the process of oleogelation and provides potential to adjust the properties of protein oleogels.