Stabilization of water-in-oil (W/O) emulsions using food grade materials

Considering the global uprise of obesity and food-linked cardiovascular diseases, the addition of water into fat-based products, in the form of water-in-oil (W/O) emulsions, seems the most promising way to reduce the fat and calorific content of these products. Although this appears to be the most promising approach in theory, lack of stability of these emulsion systems presents one of the key challenges because they are thermodynamically unstable and prone to phase separation over time. Traditionally, chemically-synthesized surfactants (e.g., polyglycerol polyriconeate (PGPR)) and/or chemically modified particles (e.g., silica particles), that contain E-numbers, have widely used as stabilizers for W/O emulsions. However, owing to the growing interests for ‘clean label’ products by consumers, such products tend to be less appealing. Consequently, there is a huge driving force from food industries to replace these chemically-synthesized materials with natural and biodegradable ingredients that will give a ‘clean label’ on the final product. This thesis addresses this research challenge of providing longer term stability to water droplets dispersed in an oil continuous matrix using biocompatible materials. The design of novel W/O emulsion droplets stabilized by an interfacial complex formation produced by a combination of nature-derived polyphenol crystals (curcumin or quercetin particles), present in the oil phase, and protein (WPI) or protein-based particles (WPM particles), in the aqueous phase, is shown in this work. The stability of these water droplets depends on the concentration of WPI or WPM particles present in the aqueous phase, as well as, the pH of the aqueous phase. An improvement of the stability was observed at an acidic pH (~ 3.0) due to hydrogen bonding and electrostatic attraction between the oppositely charged WPI or WPM particles (positive) and polyphenol crystals (negative). In addition, the effect of different processing conditions such as shear rates and temperatures on the stability of these emulsions, is shown in this thesis. It was concluded that the emulsions stabilized by interfacial complexes provided longer term stability, compared to those stabilized only by curcumin or quercetin crystals, and were stable under shear and temperatures without any coalescence or phase separation.