Pickering emulsions by regulating the molecular interactions between gelatin and catechin for improving the interfacial and antioxidant properties

Molecular interaction forces regulate the interfacial properties and play a leading role in the distribution of particles on the oil-water interface and the stability of emulsions. In this work, gelatin/catechin nanoparticles (GCNPs) were prepared at different pH and mass ratios. The GCNPs showed excellent interfacial properties when the mass ratio of gelatin to catechin was 8:1 at pH 7. The contents of free thiol and amino groups were 0.36 μmol/g and 0.38 ± 0.03 mmol/mL, respectively, and the oil-water contact angle (θow) was 61.59° at 0 min. GCNPs (1% w/v) were applied as Pickering emulsifiers to stabilize the pecan oil emulsions, the turbiscan stability index (TSI), rheological properties, and lipid peroxidation inhibition capacity were measured. The emulsion at the oil fraction (φ) value of 0.7 (v/v) had a good thixotropic recovery of 74%, lower ROOH value, and the higher inhibition rate of thiobarbituric acid reactive substance (TBARS). It was demonstrated that the φ addition enlarged the viscosity and modulus of Pickering emulsions, led to a gel-like structure and improved the emulsions stability. Our findings on regulating the non-covalent and covalent interactions between gelatin and catechin, provided novel insights about the formation of protein-polyphenol nanoparticles. These nanoparticles might serve as excellent food-grade Pickering emulsifiers for enhancing the interfacial and antioxidant properties of Pickering emulsions with a high φ.