4. Conclusions
In this work, 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 into the aqueous phase to investigate the
stability of the liquid W/CO and W/MO emulsions with a small molecule
emulsifier, GMO. W/CO emulsion without additives destabilized instantly,
whereas W/MO emulsion stayed partially stable due to extensive hydrogen
bonds between GMO and CO TAG glycerol polar heads, leading to the
desorption of interfacial GMO towards the CO phase. In MO, GMO favoured
interfacial adsorption due to the lack of polar groups, leading to
emulsion stability. The addition of hydrogen bond-forming agents and
salts in the aqueous phase significantly improved both the CO- and
MO-emulsion stability. LMP, with a large number of 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. However, the
presence of Ca with LMP led to gelation in the aqueous phase which
prevented interfacial interaction of LMP with GMO leading to a lowering
of emulsion stability. Emulsions with both oils formed weak gels due to
the formation of an extensive network of water droplet aggregates. Water
droplets were smaller in MO-emulsions than CO-emulsions, leading to a
more extensive droplet network in the former which provided higher
stability against phase separation and preservation of viscosity after 7
days storage. Interestingly, the droplet network in MO-emulsions broke
down at a lower crossover stain than the CO-emulsions, indicating weaker
links between the droplets. Overall, the aqueous phase hydrogen
bond-forming agents interacted with GMO at the interface allowing
improved stability of GMO-stabilized liquid W/CO emulsions. This
important finding could facilitate the development of highly stable
food-grade low-saturated fat tablespreads. The knowledge developed could
also improve our understanding of stability mechanisms in W/O emulsions
for other industrial and cosmetics applications.