Heteroprotein complex formation of ovotransferrin and lysozyme: Fabrication of food-grade particles to stabilize Pickering emulsions

The present work aimed to fabricate food-grade Pickering emulsions stabilized by heteroprotein complexes formed by ovotransferrin (OVT) and lysozyme (LYS) as lipid-based nutraceutical delivery vehicles. The heteroprotein complexation, as confirmed by turbidity titrations, was proved to be an effective means to prepare food-grade particles. Multiple parameters such as particle size, zeta potential and dispersion stability were characterized in screening for proper OVT–LYS particles as Pickering stabilizers. OVT–LYS particles with OVT/LYS ratio of 8:1 at pH 9.3 met all requirements of eligible Pickering stabilizers such as intermediate wettability. Titrations in the presence of sodium chloride demonstrated that primary driving force of OVT–LYS particle formation was electrostatic attraction. Afterwards, food-grade Pickering emulsions were fabricated using OVT–LYS particles. Visual observation indicated that Pickering emulsions stabilized by OVT–LYS particles at various particle concentrations and oil fractions were stable during one-month storage at room temperature, and OVT–LYS particles could stabilize high internal phase Pickering emulsions at oil fraction of 0.75. Rheological measurements revealed that viscosity and gel-like structures of Pickering emulsions were dependent on particle concentration and oil fraction. When compared with the extent of lipolysis (32.1%) in bulk oil, the extent of lipolysis (71.5%) in OVT–LYS particle-stabilized Pickering emulsion was increased by 39.4%. Curcumin bioaccessibility was increased from 16.1% to 38.3% after encapsulation of curcumin into OVT–LYS particle-stabilized Pickering emulsion. Such improved bioaccessibility demonstrated that OVT–LYS particle-stabilized Pickering emulsion was an effective delivery vehicle for curcumin.