Physicochemical stability of lycopene-loaded emulsions stabilized by plant or dairy proteins

Abstract

Lycopene is a lipophilic bioactive compound that can be challenging to deliver in vivo. To mediate this, delivery strategies, such as protein-stabilized oil-in-water (O/W) emulsions, have been suggested to improve the physicochemical stability and bioavailability of lycopene. In this research, the effects of plant (soy and pea) and dairy (whey and sodium caseinate) proteins on physical stability (droplet size, charge, interfacial rheology) and lycopene retention in canola O/W emulsions (pH = 7.0, 10% oil) were compared. Particle size distribution for sodium caseinate and pea protein-stabilized emulsions remained unchanged after 14 days of refrigerated storage, while whey and soy protein isolate-stabilized emulsions became unstable. Zeta potential was largely negative (−45 to −60 mV) for all emulsions and the lycopene concentration in plant protein-stabilized emulsions at 14 days of storage was similar to that in sodium caseinate-stabilized emulsions. Sodium caseinate formed relatively viscous films at the oil-water interface, while the other proteins formed more elastic layers. Despite this difference, both the caseinate and pea protein-stabilized emulsions were promising delivery vehicles, indicating that plant-derived proteins can be feasible alternatives to dairy emulsifiers.