Effect of hydrogel particle size embedded into oleogels on the physico-functional properties of hydrogel-in-oleogel (bigels)

Effects of incorporating hydrogel particles with various sizes (35.8–150.2 μm) into monoacylglycerol (MAG)-based oleogels at a constant hydrogel/oleogel ratio of 1:4, on the physical properties of the resultant bigels was examined. Whey protein concentrate (WPC, 3 g/100 g) and κ-carrageenan (0.8 g/100 g) were utilised as the gelling agents of hydrogels. The molten hydrogels and oleogels (8 g/100 g MAG) were prepared by mechanical mixing at different shear rates to form small-, medium-, and large-hydrogel particles dispersed in the oleogel network. The particle size significantly affected microstructural, rheological, and textural properties, and oil binding capacity (OBC) of the formed bigels. Kappa-carrageenan-based bigel with a small particle size (35.8 μm) had a denser MAG crystal network than the larger counterparts (64.4 and 47.6 μm). The presence of WPC particles inhibited the growth of MAG crystals in WPC-based bigel. Regardless of the type of hydrocolloids used, the incorporated hydrogels having small and medium particle sizes acted as active filler in the bigel matrix, increasing viscoelasticity, hardness and OBC of the resultant bigels. These results highlight the importance of particle size in building a higher degree of internal structure in the bigels that can fine-tune desired physical properties or improve delivery of bioactive compounds.