Dairy Ingredients for Food Processing

120 Chapter 4

trated to a maximum of 48% to 52% solids

or an approximately four - fold concentration.

General schematics for dual - and triple - effect

evaporators are shown in Figure 4.17.

Three different types of concentrated dairy

products are commonly used as ingredient:

concentrated, evaporated, and sweetened con-

densed milk. The three types of non - fat con-

centrated forms are also available as nonfat

concentrate, evaporated, and nonfat sweet-

ened condensed milks. Details of these prod-

ucts are discussed elsewhere (Chapter 5 ).

Drying

Many dairy ingredients are sold as a dry

powder with a moisture content of approxi-

mately 3%. If moisture content is above 5%

the shelf life of dairy powders is drastically

reduced; Maillard browning reaction occurs

and caking and lumping is increased. Maillard

browning not only affects color but also is

responsible for off fl avor development.

Drying is the fi nal step in ingredient manu-

facture. Removal of moisture is an expensive

fi lm evaporators are linked in a series they
are referred to in terms of effects. For
example, if three shell - in - tube evaporators
are linked in series, they are referred to as a
triple - effect evaporator. The temperature at
which milk boils is a function of the extent
of vacuum applied. In multiple - effect evapo-
rators, each successive evaporator has a
greater vacuum than the preceding unit.
Vapor released from the concentration
process is compressed and used as a heating
medium. Such units are called evaporators
with thermocompression.
Removal of water is an energy - intensive
process, and thermocompression can mini-
mize the energy used in the concentration
process. A two - effect falling fi lm evaporator
with thermocompression requires about
0.25 kg steam to evaporate 1 kg of water. In
a fi ve - effect evaporator with thermocom-
pression, 0.20 kg of steam is required for
each kilogram of water evaporated. Without
thermocompression, 0.6 and 0.4 kg steam,
respectively, would be needed for the removal
of one kilogram of water. Milk is concen-

Figure 4.17. General schematic for a double effect evaporator with thermo - mechanical vapor recompression.

3 3 33

2

(^19)
5 5
4
7
6
10
8 8
1 Balance tank
2 Plate heat exchanger
3 Tubular heat exchanger
4 Calandria, first effect
5 Collector
6 Calandria, second effect
7 Thermal recompressor
8 Circulation pumps
9 Vacuum pumps
10 Discharge pump
Milk
Steam
Cold water
Vacuum
Condensate
Vapour