Does particle size matter for soy protein nanoparticles in the fabrication and lipolysis of pickering-like emulsions?

Abstract

Enzyme-mediated nanostructures have gained increasing interests and shown promising applications in functional delivery for food and pharmaceuticals. In our previous study, we fabricated three types of spherical soy protein nanoparticles (SPNP) by flavorzyme to different degree of hydrolysis (DH, 3%, 7% and 11%). These SPNPs exhibited similar subunit composition, secondary structure and surface properties, but differ in size, which is 89 nm, 106 nm and 151 nm, respectively. This study further applied them in emulsion systems for functional delivery. We systematically studied the emulsifying activities, interfacial properties including wettability, interfacial packing pattern, interfacial adsorption and dilatational rheological behavior of SPNPs, and their performance in modulating lipolysis of the emulsions under the influence of lipase, bile salts, pepsin and trypsin. All SPNPs behaved as Pickering-like stabilizers with moderate wettability at oil-water interface with three phase contact angle of 92–101°, and the SPNP with the smallest size has better emulsifying activities (D3,2 = 3.22 ± 0.00 μm in SDS solution) than native soy protein isolate (SPI) (D3,2 = 4.04 ± 0.03 μm in SDS solution). These SPNPs formed similar viscoelastic oil-water interfaces (Ed' = 20.2–21.5 mN/m), which were more glassy-like with weak in-plane interactions compared to SPI (Ed' = 28.6 ± 0.5 mN/m). All SPNPs can delay lipolysis of emulsions by lowering the access/replacement of lipase and bile salts and depressing the proteolysis by trypsin at interface in similar ways. Our work elucidated the role of particle size of enzyme-mediated plant protein-based particle in emulsion stabilization and lipolysis control, and is expected to give the theoretical support for the design of functional food emulsions with controllable energy intake.