502 Chapter 19
ticle agglomerates, and modifi cation of the
melting quality (Beckett, 1999 ). Because the
conching process can sometimes employ
temperatures as high as 70 ° C to 80 ° C and
times as long as several days, fl avor reaction
products, such as Maillard reaction products,
formed during this step contribute to the
fl avor profi le of the fi nished chocolate. The
composition of the dairy solids used in choc-
olate manufacturing has a strong infl uence on
the development of the desired fl avor profi le
during conching.
Emulsifi ers and additional cocoa butter
are often added at the end of conching to
standardize the fi nal product and adjust the
fl ow properties of the fl uid chocolate mass to
the fi nal specifi cations suitable for forming
the desired fi nished product. Lecithin is by
far the most common emulsifi er used in the
chocolate industry (Hoskin and Dimick,
1994 ), although the ammonium phosphatide
known in the trade as YN is also allowed in
some countries. In addition, polyglycerol
polyricinoleate (PGPR) is also widely used
in chocolate products. The amount of emulsi-
fi er employed typically falls within the
range about 0.2% to 0.6% (Minifi e, 1980 ).
Flavoring materials are also added at this
point, with vanillin and natural vanilla the
most commonly added in the United States.
Conching and standardization is followed
by tempering, a mixing and cooling process
using specifi c temperature ranges to cause a
small part of the liquid cocoa butter to be
crystallized in the appropriate polymorphic
form. These crystals act as nucleation sites
when additional cocoa butter crystallizes
during solidifi cation of the chocolate, thereby
preventing subsequent surface discoloration
known in the trade as fat bloom. They also
provide the appropriate texture to the fi nished
product. Failure to produce the correct crys-
talline form not only results in problems for
the manufacturer, but also gives a product
without the gloss, snap, and color normally
expected by the consumer (Bricknell and
Hartel, 1999 ; Aguilar and Ziegler, 1993 ).condense fresh whole milk with sugar and
either dry this mixture to produce milk crumb
or blend the mixture with chocolate liquor
and then dry the resulting mixture, producing
milk chocolate crumb (Bouzas and Brown,
1995 ). Additional aspects of both these so -
called milk - powder - based chocolates and
crumb - based chocolates are discussed in the
next section.
The second stage in chocolate processing
is a particle size reduction process known in
the trade as refi ning, essentially a fi ne grind-
ing operation in which the coarse paste is
passed through a roller mill or media mill to
reduce the particles of crystalline sugar,
fi brous cocoa matter, and milk solids to a
nominal diameter of 15 to 50 μ m. The parti-
cle size of chocolate is extremely important
to the overall quality of chocolate, hence the
refi ning process which controls particle size
is crucial (Beckett, 1999 ). A particle size
greater than about 30 micrometers will result
in a chocolate that is gritty in the mouth,
whereas a particle size of less than around 18
micrometers can result in a chocolate with a
very high viscosity and yield stress that can
be diffi cult to handle during downstream
processing.
The refi ned chocolate paste is then
conched, a step critical to fl avor and texture
development. Conching is a high - shear
mixing process that works chocolate fl ake
and crumb into a fl uid paste, embracing a
wide range of phenomena including fl avor
development, reliquifi cation of the chocolate
paste, gloss development, destruction of par-
Table 19.1. Typical milk - powder - based milk
chocolate formula.
Ingredient % (w/w)
Sucrose 46.60
Cocoa butter 20.00
Whole milk powder 21.00
Cocoa mass 12.00
Lecithin 0.30
PGPR 0.05
Vanillin 0.05