506 Chapter 19
which proteins, fat globules, and air cells are
dispersed (Aguilar and Ziegler, 1993 ). A
modifi cation of typical spray dried WMP that
is available to chocolate manufacturers is the
so - called high free fat whole milk powder.
(Liang and Hartel, 2004 ). To manufacture
this product, the fl uid whole milk is separated
into skim and cream streams, which are co -
spray - dried in a way that the bulk of the milk
fat is on the surface of the milk powder par-
ticles, thereby offering similar functional
benefi ts of roller - dried milk powder.
The major disadvantage of whole milk
powder in chocolate making, regardless of
whether it is roller dried or spray dried, is its
relatively short shelf life. A recent study
showed that WMP lost fresh fl avors and
developed grassy off fl avors by three months
of age (Lloyd, et al., 2009 ). By six months of
age, the same milk powder exhibited painty
off fl avors, which could subsequently be
detected in chocolate made with the milk
powder. The development of painty off -
fl avors can be delayed by packing the WMP
in bags with an oxygen barrier layer and
nitrogen - fl ushing the headspace at the time
of packaging. Nevertheless, sourcing and
maintaining working stocks of good quality
WMP can be a challenge for chocolate
makers, particularly in parts of the world in
which nitrogen - fl ushing and high oxygen -
barrier packaging of WMP are not common
practices.Skim Milk Powder
Spray - dried skim milk powder is generally
thought to produce chocolates with a less
well rounded dairy fl avor profi le when com-
pared to chocolates produced with crumb or
WMP (Campbell and Pavlacek, 1987 ).
Because SMP has a fat content of less than
1%, it is less sensitive to development of off
fl avors than WMP, and therefore has a sub-
stantially longer shelf life. This longer shelf
life, in combination with widespread avail-
ability in most parts of the world and rela-Whole Milk Powder
Historically, roller - dried whole milk powder
has been the preferred milk powder for choc-
olate production. Roller - dried whole milk
powder is traditionally used in milk choco-
late at the level of 12% to 25% by weight of
the chocolate (Hansen and Hansen, 1990 ).
Roller drying is accomplished by the direct
heating of a thin layer of evaporated milk on
a rotating drum, producing a sheet of dry
milk that is subsequently powdered in
hammer mills. The resulting powder consists
of compact particles with very little occluded
air and sharp edges as a result of crushing
(C á ric and Kalab, 1987 ).
The main advantage of roller - dried whole
milk powders is the high content of free fat
which results in favorable rheological prop-
erties during mixing and conching, allowing
reductions in cocoa butter and energy con-
sumption (Attaie, et al., 2003 ). The principal
disadvantage of roller - dried whole milk
powder is that the process is economically
unfavorable compared to spray drying, due
to lower throughput through the drying
process, as well as the requirement for more
specialized equipment. These economic
implications generally have caused the dairy
industry to move toward spray drying as the
preferred method of producing milk powder.
The authors are aware of several companies
in Europe currently supplying roller - dried
milk powder, but in the United States and
most of the rest of the world, roller - dried
milk powder is very diffi cult and costly to
source.
Spray drying is currently the most common
method of producing whole milk powder for
chocolate manufacture. The powder micro-
structure is affected by the method of atomi-
zation and dryer operation conditions (C á ric
and Kalab, 1987 ), with the strongest infl u-
ence on the internal porosity of the resulting
milk powder particles and the amount of free
fat. In spray - dried whole milk powder, amor-
phous lactose forms a continuous matrix in