156 Chapter 6
are added as microencapsulated ingredients,
whereas others are directly incorporated into
milk powders (Augustin, 2003 ).
The well established role of calcium in
bone health has driven interest in the devel-
opment of calcium - fortifi ed milk products
(Augustin and Williams, 2002 ). Insoluble
calcium salts may be dry blended with milk
powders but there are potential problems
with separation during powder storage and
settling of these salts when used in reconsti-
tuted milk applications. Soluble calcium salts
may be added, but their addition must be
carefully managed to avoid protein precipita-
tion of milk during heating because the direct
addition of soluble calcium salts increases
calcium activity and reduces the pH of the
milk, making it more susceptible to coagula-
tion. A strategy based on the addition of
soluble calcium salts in combination with
orthophosphates for management of calcium
activity and pH control has been applied to
produce calcium - fortifi ed milk powders with
up to 8 g additional calcium/kg powder. This
approach involves fortifi cation of milk fol-
lowed by a low - or high - heat treatment of
milk prior to concentration and drying
(Williams et al., 2005 ).
Probiotics have a role in gut health and
have been added to a range of foods. They
are generally supplied as freeze - dried cul-
tures for addition to foods. It is possible to
produce a probiotic milk powder by spray
drying reconstituted skim milk containing L.
paracases NFBC 338 with a probiotic sur-
vival of 85%. It was further demonstrated
that the probiotic powder could be added to
cheese milk for production of probiotic
cheddar cheese (Gardiner et al., 2002 ).
The incorporation into foods of omega - 3
fatty acids has been increasing due to their
link with improved heart, eye, and brain
function. Spray - dried milk powder enriched
with omega - 3 oils may be produced from
full - cream milk supplemented with a range
of omega - 3 oils (e.g., fi sh oil) prior to spray
drying. Special care must be taken in produc-et al., 2002 ) can lead to an increase in free
fat of spray - dried milk powders.
Signifi cant increases in free fat in powder
also may be achieved by modifying the
method used for manufacture. Higher free fat
powders were obtained by (a) increasing the
temperature of the concentrate fed into the
spray dryer or decreasing the inlet air tem-
perature and increasing the outlet air tem-
perature of the spray dryer (Vilder de et al.,
1976, 1979 ), (b) combining skim concentrate
with cool cream or cream homogenized at a
high temperature prior to drying (Clarke and
Augustin, 2005 ), or (c) exposing full - cream
milk powder to high shear and a high tem-
perature in a twin - screw co - rotating proces-
sor (Koc et al., 2003 ).
Comparisons between the performance of
roller - dried full - cream milk powder, spray -
dried with added butter oil, and spray - dried
full - cream milk powder with a high free fat
content indicated that free fat was a major
infl uence on the rheological properties of
chocolate (Franke et al., 2002 ). Examination
of spray - dried milk powders produced by
mixing milk fat fractions into skim milk prior
to drying, spraying milk fat fractions onto
dried powder, or a combination of these
showed that there was a good correlation
between free fat content of the spray - dried
powders and viscosity of chocolate mass,
although other factors such as the microstruc-
ture and interfacial properties of the powders
also had a role (Attaie et al., 2003 ).
Milk Powders with Health - promoting
Functional Ingredients
The interest in the development of health -
promoting foods has led to research in func-
tional milk powders for health and well - being.
These include milk powders enriched with
well - known nutrients such as minerals (e.g.,
Ca) and vitamins (e.g., vitamins A and D), and
functional ingredients of more recent interest
such as omega - 3 oils, probiotics, and phytos-
terols. Some of these functional ingredients