Instant Emulsions - Food Colloids: Self-Assembly and Material Science - page 415

Therefore the issue of how such competing processes affect overall system
morphology and properties will be considered here.
Generally, the production of an emulsion requires a high energy input
(e.g., using high-pressure homogenization), which adds significantly to
production costs. The minimum energy requirement for emulsification can be
defined at the simplest level by the thermodynamic equation

DG ¼ g DA, (1)

where g is the interfacial tension, and DA the change in surface area of the
dispersed phase from a phase-separated system to an emulsion system of
specific dispersed phase surface area.
Processing routes such as high-pressure homogenization, which are usually
required to achieve effective droplet break-up, are surprisingly inefficient. They
typically require an energy input greatly in excess of that given by Equation (1),
so that most of the energy supplied is dissipated in the form of heat. Therefore,
the ability to develop and design emulsion systems for which the energy input
requirement is minimized is of significant scientific and commercial interest.

28.2 Emulsification
Several authors 1-9 have investigated instant or 'spontaneous' emulsions, but
not in the field of food science, and not typically utilizing dry powders to aid the
structuring and emulsification processes. Water-continuous emulsions from
water-in-oil (W/O) microemulsions have been described, 1 as has the spontane-
ous formation of highly concentrated W/O emulsions, 2,3 and the use of
optimized water/oil/surfactant ratios 4 as concentrates to form mini-emulsions
upon the addition of a large amount of water. 5 The formulation of spontaneous
emulsions has also been suggested 6,7 as an alternative to the use of ultrasonic
and high shear devices, and the dynamics of spontaneous emulsification for the
fabrication of O/W emulsions has been discussed. Furthermore, some new
methodologies 8 and mechanisms 9 have been described to explain the process of
spontaneous emulsification.
The work reported here probes the effectiveness of using food emulsifiers to
create instant emulsions. Powders for structuring, emulsification, taste and
microbiological stability are delivered as a slurry in oil. The cold O/W emul-
sions can then be formed rapidly with minimal mechanical agitation. The
dispersion of hydratable polymers and added solids in the oil serves the same
function as mixing a polymer with a non-solvent prior to dissolution in a true
solvent: the particles hydrate rapidly and independently in the presence of
water on agitation. The conjunction of these two processes results in simulta-
neous emulsification of the oil and hydration/dissolution of the solids, which
thicken and structure the aqueous phase, as well as kinetically trap the
dispersed oil phase. Only moderate shear, as can be produced by hand stirring,
is required to develop the final 'structured' emulsion. The result is a paste-like
O/W emulsion whose properties depend upon thickener levels, oil phase