Stabilization of liquid water-in-oil emulsions by modifying the
interfacial interaction of glycerol monooleate with aqueous phase
ingredients
Abstract
Glycerol monooleate (GMO)-stabilized liquid water-in-vegetable oil
(W/VO) emulsions are difficult to stabilize due to the desorption of GMO
from the W-VO interface towards the oil phase. This work improved the
stability of GMO-stabilized liquid 20 wt% water-in-canola oil (W/CO)
emulsion by modifying the dispersed aqueous phase composition with
hydrogen bond-forming agents. As a control, 20 wt% water-in-mineral oil
(W/MO) emulsion was also utilized. Different concentrations of hydrogen
bond-forming agents (citric acid (CA), ascorbic acid (AA), low methoxyl
pectin (LMP)) with and without salts (sodium chloride (S) or calcium
chloride (Ca)) was added to the aqueous phase before emulsification,
which enhanced emulsifier binding to the water-oil interface. The
emulsions were characterized by phase separation, stability against
accelerated gravitation, microstructure and rheology. W/CO emulsion
without any aqueous phase additive destabilized instantly, whereas W/MO
emulsion stayed stable. The addition of hydrogen bond-forming agents and
salts significantly improved emulsion stability. LMP, with many hydrogen
bond-forming groups, was able to provide the highest emulsion stability
after 7 days in both oils compared to AA, CA and their mixtures with S.
Emulsions with both oils formed weak gels with viscous and elastic
characteristics due to the formation of an extensive network of water
droplet aggregates. Overall, the hydrogen bond-forming agents interacted
with GMO at the interface, thereby improving their presence at the water
droplet surface, allowing significantly improved stability of
GMO-stabilized liquid W/CO emulsions. The knowledge developed in this
research can be useful in applying GMO in stabilizing liquid
water-in-oil emulsion without using any crystal network.