Glycerol-regulated interfacial adsorption behavior of whey protein isolate for stable high internal phase emulsion gels: Impact on lipid oxidation and curcumin bioaccessibility

High internal phase emulsions (HIPEs) are widely used to encapsulate unsaturated fats and fat-soluble bioactive ingredients in food, nutraceutical, cosmetic, and pharmaceutical applications. This study successfully developed stable emulsion gels by substituting water with glycerol in the whey protein isolate (WPI) aqueous phase, using glycerol mass percentages of 30%, 60%, and 90%. Increasing the glycerol ratio resulted in aggregation and an increase in particle size of whey isolate proteins, as well as enhanced protein hydrophobicity. Notably, the interfacial tension between the WPI/glycerol mixture and fish oil decreased with higher glycerol content. While a higher proportion of glycerol resulted in increased adsorption of interfacial proteins in HIPEs, it also led to a decrease in the concentration of interfacially adsorbed proteins due to the larger surface area. Additionally, higher glycerol ratios improved the thermal, centrifugal, and freeze-thaw stability of the HIPEs. The HIPEs fabricated with the WPI/glycerol aqueous phase exhibited reduced oxidation of unsaturated oils and enhanced gastrointestinal stability and bioaccessibility of loaded curcumin compared to pure fish oil. The study offers a novel approach for the straightforward preparation of stable protein-based HIPEs, providing a new strategy for oxidative protection of unsaturated fats and enhancing the bioaccessibility of fat-soluble bioactive ingredients.