Professor Toronto Metropolitan University Toronto, Canada
Abstract: The global rise of obesity and cardiovascular diseases associated with high consumption of saturated fat has encouraged the food industry to develop healthier products. Water-in-oil (W/O) high internal phase emulsions (HIPEs) represent one approach to the replacement of fat in processed foods.
Objectives: This research aimed to: i) develop W/O HIPEs stabilized by fat crystals, and ii) study the effect of the addition of fat on the properties of the HIPEs.
Methods: The W/O HIPEs consisted of 76 wt% water, with the continuous oil phase composed of soybean oil (19.7 to 22.1 wt%), fully hydrogenated soybean oil (HSO) (0 to 2.4 wt%), and PGPR (1.9 wt%). Microstructure (light microscopy), droplet size distribution (pulsed NMR), and viscoelasticity (strain-controlled rheology) were evaluated for 28 days at 5 °C.
Results: Addition of HSO did not alter initial average droplet size, but presence of more fat caused a broader droplet size distribution over time. The formation of clustered fat crystals and closer droplet-droplet contact may have contributed to physical instability. The rigidity of the HIPEs with 1.2 wt% or 2.4 wt% HSO was greatest, and these also showed the highest brittleness and lower recovery in thixotropy.
Significance: This research showed that the consistency of W/O HIPEs can be significantly modulated by addition of small amounts of solid fat; however, physical stability was also affected.