Novel high internal phase emulsions with gelled oil phase: Preparation, characterization and stability evaluation

Novel high internal phase emulsions (HIPEs, O/W) with gelled oil phase were fabricated via a facile approach using all-natural ingredients. Oil phase of HIPEs was oleogelated with beeswax (BW), and the effects of BW concentration (0–6%) on structural properties of the emulsions and stability of β-carotene were highlighted. Microstructural observation indicated that the oil droplets (3–4 μm) of the emulsions were tightly packed with protein bridges at the interfaces and BW crystals inside the droplets. BW crystals were also confirmed by XRD analysis, and the increase in BW concentration led to higher crystallinity in HIPEs. Oleogelation of the oil phase offered the emulsions with improved stability against centrifugation, heating and freeze-thawing, and the HIPE with 3% BW presented the best stability. Small amplitude oscillatory shearing tests revealed that storage modulus of the samples was dependent on BW concentration, and creep-recovery evaluation indicated that the HIPEs with BW had higher resistance over deformation. Large amplitude oscillatory shearing tests showed that the HIPEs with higher content of BW (4.5, 6%) had stain thinning behavior, while those with lower content of BW (0, 1.5, 3%) presented weak strain overshoot characteristics. When β-carotene (up to 2.25%) was incorporated in the oil phase of the emulsions, its stability against light and thermal treatment was significantly improved with the presence of BW, and the emulsion with 3% offered the highest protection. These information suggested that oleogelation of the oil phase facilitated the formation of stable HIPEs and can better behave as carriers for liable bioactives.