Chemistry Reference
In-Depth Information
Fig. 10.8
Electron microscope picture of a cocoa butter emulsion with 30% included
water, showing the microstructure of a continuous fat phase incorporating oil and triglyce-
ride crystals and water droplets which have a fat crystal shell around them (scale bar is
10
ยต
m). Reproduced from Norton et al. (2009). Copyright 2009, with permission from
Elsevier.
One of the advantages of shells is that they cause scattering of the
cracks when the structure is broken. Thus, they can be used to hide
material from the rest of the structure, i.e. water which is not seen by
the materials in the continuous phase of the chocolate matrix, but also
salt in sauces soups, etc. This is discussed in a later section of this
chapter.
10.3.2
Duplex emulsions
So what is a duplex (or double) emulsion? An example is given in
Fig. 10.9, in which a primary emulsion of water in oil was produced
using PGPR as the emulsifier. This particular emulsifier is often used for
oil-continuous emulsions, as it is polymeric in nature and gives a very
stable elastic interface. Once formed, the primary emulsion is then used
as the included phase in the production of an oil-in-water emulsion. This
is achieved by using a second emulsifier (often a low molecular weight
material). By doing this, a duplex (or double) emulsion is produced.
One of the problems with duplex emulsions that has limited their
application in real foods is that they are inherently unstable. This is be-
cause there are two oil/water interfaces, which have different curvatures.
