Chemistry Reference
In-Depth Information
Fig. 10.9
A photomicrograph of a w/o/w duplex emulsion stabilised with PGPR. The
inner droplets are approximately 10
µ
m and the secondary emulsion has droplets of
approximately 100
µ
m.
As the emulsifier moves between interfaces, they become identical and
the structure collapses. The most common way of stopping this from
happening is to have a large emulsifier which aggregates at one of the
interfaces to give gel-like structures, hence the reason that PGPR is used
in studies on duplex emulsions for foods. The second problem that exists
is that the primary emulsion is damaged in the second emulsification
process. This results in various levels of release of the contents of the
primary emulsion contents during the process. Again, it has been shown
that PGPR is a good emulsifier to use, as it is very stable in the process.
So duplex emulsions can be made, but the use of PGPR is not ideal
as it is not generally allowed in foods, although its use is allowed in
chocolate. Even if PGPR was more widely allowed in foods, duplex
emulsions produced with this emulsifier are not stable for the shelf life
of a product. On storage, droplets tend to change size as a consequence
of osmotic pressure differences between different phases.
10
.
3
.
2
.
1
Fat replacement
For fat replacement, the use of duplex emulsions has some inherent
advantages. The most significant one is that if the primary emulsion
is constructed to remain stable throughout the lifetime of the product,
at least until it is within the human stomach, then the product will be
perceived to have a much higher fat content than is actually present.
However, if this dream is to be realised, then a duplex emulsion has to
be made that is stable throughout the shelf life and usage of the product
and only using food-allowed materials.
