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.
Keywords: water-in-oil emulsion; glycerol monooleate; hydrogen
bond-forming agents; emulsion stability; interfacial interaction