homogenization for “cleaner”
Emulsions are dispersions of immiscible fluids. Most sauces and
dressings are oil-in-water emulsions (O/W) in which the dispersed
phase, commonly a vegetable oil, is dispersed into an aqueous
phase in the presence of emulsifying molecules. Their production
generally involves the application of mechanical forces (
homogenization) to induce oil droplet size reduction and dispersion into the
continuous water phase.
Emulsions are by nature unstable systems. Due to the lower
density of the oil droplets relative to the aqueous continuous
phase, gravity causes the droplets to move upward and form a
cream layer during storage. For this reason, the development of
long-term, stable, reduced-fat emulsions with adequate textural
properties represents an important industrial challenge. Some of
the most relevant factors influencing emulsion destabilization are
the size of the oil droplets, the viscosity of the continuous phase,
and the volume fraction of the oil.
Decreasing the size of the droplets and increasing the viscosity
of the continuous phase prevent cream layer formation. A reduction in the oil volume fraction diminishes the packaging densities
of the fat droplets, the viscoelastic properties of the continuous
phase, and, consequently, the tendency to cream. Hence, substituting fat with fat replacers and thickening agents is a primary strategy for enhancing emulsion stability. Such replacement ingredients
increase the continuous phase viscosity, which impedes the upward
migration of the oil droplets and increases overall viscoelasticity.
However, some ingredients, such as xanthan gum, guar gum, and
inulin, strongly affect the sensory characteristics of foods at the
concentration needed to obtain suitable structural properties. This,
together with the industrial trend toward cleaner and simpler labels
has prompted the search for new alternatives. One of the most
promising is an emerging technology called ultra-high pressure
Many sauces and dressings are conventionally high in fat. For example, traditional mayonnaise, which
is consumed worldwide, contains 75–80 wt% oil. From a technological perspective, the leading role of
fat in the structure and sensory properties of emulsions makes it very challenging to reduce or replace
fat in such products.