Dairy Chemistry And Biochemistry

34 DAIRY CHEMISTRY AND BIOCHEMISTRY

has a pronounced tendency to cake owing to its very high lactose content
( - 70%).
Problems arising from the crystallization of lactose in milk and whey
powders may also be avoided or controlled by pre-crystallizing the lactose.
Essentially, this involves adding finely divided lactose powder which acts as
nuclei on which the supersaturated lactose crystallizes. Addition of 0.5 kg of
finely ground lactose to the amount of concentrated product (whole milk,
skim milk or whey) containing 1 tonne of lactose will induce the formation
of c. lo6 crystals ml- l, about 95% of which will have dimensions less than
10pm and 100% less than 15 pm, i.e. too small to cause textural defects.
Diagrams of spray dryers with instantizers are shown in Figures 2.10 and
2.11.

Feed-[ I /Hot air

Cyclone separators

(?/

II I1

Crystalization belt

b Vibrofluidizer

Hammer mill

Product out

Figure 2.10 Schematic representation of a low temperature drying plant for whey (modified

from Hynd, 1980).