2009_Book_FoodChemistry

528 10 Milk and Dairy Products
is consequently preferred. The solubility is poor
due to the denaturation of whey proteins. The
product is clearly brown owing to the Maillard
reaction.
In spray drying, the milk concentrate (30–55%
solids) is finely dispersed in the spray tower by
centrifugal atomization or by nozzle atomization
and dried with hot air (150–220 ◦ C) cocurrently
or countercurrently. The water content drops to
6–7% in 0.5–1 s. A further decrease to 3–4% is
achieved by after drying in a vibration fluid bed
with hot air (130–140 ◦ C).
Particles with a diameter in the range of 5 to
100 µm consist of a continuous mass of amorphous
lactose and other low-molecular components,
which includes fat globules, casein micelles,
whey proteins and usually vacuoles. When
the powder absorbs water, lactose crystallizes at
a w > 0.4, causing agglomeration. During drying,
the temperature of the particles normally does not
rise above 70 ◦ C. Therefore, the whey proteins do
not denature and remain soluble. Many enzymes
are still active. Storage problems are caused by
the Maillard reaction and by fat oxidation in the
case of fat-containing powders. Foam dried products
can have excellent properties (aroma, solubility).
Other dehydrated dairy products, in addition to
whole milk or skim milk powders, are manufactured
by similar processes. Products include dehydrated
malted milk powder, spray- or rollerdried
creams with at least 42% fat content of their
solids and a maximum 4% moisture, and butter
or cream powders with 70–80% milk fat. Dehydrated
buttermilk and lactic acid-soured milk are
utilized as children’s food.
Adaptation of infant milk product formulation to
approximate mothers’ milk can be achieved, for
example, by addition of whey proteins, sucrose,
whey or lactose, vegetable oil, vitamins and trace
Table 10.27. Composition of dried milk products (%)
1 2 3 4
Water 2.7 3 4.6 3.3
Protein 26.5 38.2 13 91.4
Fat 27.4 0.9 1.1 0.9
Lactose 37.7 49.6 73 0.2
Minerals 5.7 8.2 8.2 4.1
1: whole milk powder; 2: skim milk powder; 3: whey
powder; 4: caseinate
elements and by reduction of minerals, i. e., by
a shift of the Na/K ratio.
The compositions of some dehydrated dairy products
are illustrated in Table 10.27.
10.2.6 Coffee Whitener
Coffee whiteners are products that are available in
liquid, but more often in dried instant form. They
are used like coffee cream or condensed milk.
A formulation typical of these products is shown
in Table 10.28. In contrast to milk products, plant
fats are used in the production of coffee whiteners.
Caseinates are usually the protein component.
The most important process steps in the production
are: preemulsification of the constituents
at temperatures of up to 90 ◦ C, high-pressure homogenization
(cf. 10.1.3.4), spray drying, and instantization
(cf. 10.2.5).
10.2.7 Ice Cream
Ice cream is a frozen mass which can contain
whole milk, skim milk products, cream or
butter, sugar, vegetable oil, egg products, fruit
and fruit ingredients, coffee, cocoa, aroma
substances and approved food colors. A typical
formulation is 10% milk fat, 11% fat-free milk
solids, 14% saccharose, 2% glucose syrupsolids,
0.3% emulsifiers, 0.3% thickener, and
62% water. The thickeners, mostly polysaccharides
(cf. Table 4.15), increase the viscosity
and the emulsifiers destabilize the fat globules,
favoring their aggregation during the freezing
process.
Table 10.28. Typical formulation of coffee whiteners
Constituent Amount (%)
Glucose syrup 52.6
Fat 30.0
Sodium caseinate 12.0
Water 3.15
Emulsifiers 1.6
K 2 HPO 4 0.6
Carrageenan 0.05
Color and aroma substances