142 Chapter 6
rate heat treatment of each of these streams.
The skim milk is given a low - heat treatment
and concentrated by evaporation, whereas
the cream is subjected to a high - heat treat-
ment. The skim concentrate and cream are
then combined back into a full - cream milk
concentrate and spray dried. Full - cream milk
powders produced by the alternative pro-
cesses have similar fl avor and physical
characteristics to powders prepared by the
traditional process. Fouling of the evapora-
tors is expected to be reduced with the use of
the alternative process (Hols and Van Mil,
1991 ).
It is essential that milk powders be made
from good - quality milk and that their com-
positional and technical specifi cations relate
to end - use requirements (Jensen, 1990 ).Standardization of Dairy Streams
The standardization of dairy streams is essen-
tial to ensure that the dry milk products meetMilk Powder Processing
The unit processes in the manufacture of
dry milk products include standardization of
the milk streams, preheating, concentration,
homogenization, and drying. The generalised
processes for the manufacture of a selected
range of dry milk products, starting with full -
cream milk as the raw material, are given in
Figure 6.1. The approximate compositions of
the major traditional milk powder products
are as follows: skim milk powder (36%
protein, less than 1% fat, 51% lactose, 8%
ash, 3% to 4% moisture) and full - cream milk
powder (26% protein, 27% fat, 38% lactose,
6% ash, moisture 3%).
The normal process for the manufacture
of full - cream milk powder involves a preheat
treatment of the full - cream milk, followed
by thermal evaporation, homogenization,
and spray drying. An alternative process
involves the separation of full - cream milk
into skim milk and cream followed by sepa-
Figure 6.1. Flow chart for manufacture of selected dry milk products.