Tailoring microstructures of oleogel-based HIPEs to modulate oral processing properties: Rheology, tribology and mastication effects

High internal phase emulsions (HIPEs, 80 wt%) with different structures were developed by using different oleogelators (beeswax and ethyl cellulose) and emulsifiers (whey protein isolate and OSA starch) via a facile shearing approach. The effects of the oleogelators and emulsifiers on the stability and oral processing properties were investigated. The addition of oleogelator resulted in smaller particle sizes and higher accelerated centrifugal stability. Microstructural observations indicated the droplets were tightly packed to form oil-in-water HIPEs. Rheology tests showed that the addition of the oleogelators resulted in strain-thinning behavior and weak strain overshoot for OSA and WPI stabilized HIPEs, respectively. Tribology tests suggested that emulsifiers dominated the lubrication properties of the mixing regime, whereas oleogelators were crucial to the lubricating effects of the hydrodynamic regime. Instrumental mastication assays revealed that the WPI-HIPEs required stronger chewing force, and the addition of oleogelator weakened the normal force. After being masticated by the bionic chewing robot, droplet coalescence and phase separation occurred in the HIPEs, which was attenuated by the addition of oleogelators. These findings will assist in designing the structures of desirable textural attributes and support the creation of functional foods.