Tailoring yield stress and viscosity of concentrated microgel suspensions by means of adding immiscible liquids

Adding a small amount of secondary immiscible liquid (<1 g/100 g) to a suspension significantly alters rheological properties by creating a network of fluid bridges between particles or reinforcing an existing space-spanning network; these additional forces are termed capillary forces. Rheological properties of concentrated microgel suspensions are tunable by compositional and processing measures including solid content or particle size distribution; however, these approaches may lead to technical difficulties and further processing steps. This study aimed to test the effect of adding a small amount of oil on the rheological properties of fat-free fresh cheese, a water-continous concentrated suspension of dairy microgel particles. A significant increase of the low-shear viscosity (<1/s) and yield stress was observed by blending food-grade canola oil. Confocal scanning laser microscopy showed oil distribution between microgel particles and no apparent microstructural changes.