Pickering emulsions stabilized by hemp protein nanoparticles: Tuning the emulsion characteristics by adjusting anti-solvent precipitation

Abstract

Hemp protein is an important dietary source rich in cannabinoid (CBD) and comprehensive amino acids, but its application in food is limited due to its poor emulsibility and solubility. In this study, hemp seed proteins were used to produce hemp protein nanoparticles (HPNs) by anti-solvent precipitation for the first time using formic acid as solvent. During anti-solvent precipitation, the supersaturation can control the number and size of the nanoparticles produced. Three important factors, including the solvent-antisolvent ratio, the dropping rate and the stirring rate were used to adjust the supersaturation. At moderate supersaturation, such as 1:10 (v/v) solvent-antisolvent ratio, a dropping rate of 15 mL min−1 or a stirring rate of 1000 rpm, HPNs exhibited smaller particle size (∼130 nm), greater ζ-potential (∼50 mV) and stronger wettability to water compared to HPNs prepared under high or low supersaturation. HPNs prepared under moderate supersaturation exhibited more random coil (24.83%) and β-sheet (61.75%), exposing more hydrophobic amino acid residues. All O/W Pickering emulsions were able to remain stable during 3 weeks storage at 20 °C. In the presence of HPNs prepared under moderate supersaturation, the emulsions exhibited larger droplet size than HPNs prepared under low or high supersaturation, increasing from ∼300 nm to ∼450 nm. Because many HPNs were separated from the interface, Pickering emulsions prepared with these HPNs exhibited higher apparent viscosity than HPNs prepared under low or high supersaturation. This research will expand the way of hemp proteins utilization, and also broaden the preparation method and regulation means of protein-based Pickering emulsions.