2009_Book_FoodChemistry

538 10 Milk and Dairy Products
Table 10.36. Protein, lactose and mineral contents of
whey products a
Product DM b Protein Lactose Minerals
(%) (%) (%) (%)
Skim milk 9.0 36 53 7
Whey (from
coagulating
with rennet) 6.0–6.4 13 75 8
Whey (from
coagulating
with acid) 5.8–6.2 12 67 14
Demineralized whey
powder 12–13 85 1–2
Whey protein powder c
I 47 44 9
II 74 20 6
a Average values are expressed as % of dry matter.
b Dry matter.
c After one (I) and two (II) ultrafiltrations.
Fig. 10.31. Principle of electrodialysis of whey. 1 cathode,
2 cation membrane, 3 anion membrane, 4 anode
• Preliminary concentration of the whey to
50–55% dry matter in falling-film evaporating
systems (thermal or mechanical vapor compression),
followed by spray drying (one step
or two step with subsequent vibraton fluid
bed).
• Preliminary concentration of the whey to 21–
25% dry matter by reverse osmosis (hyperfiltration),
followed by concentration to 50–
55% dry matter via falling-film evaporators
and spray drying.
The composition of whey powder is presented in
Tables 10.27 and 10.36.
10.2.10.2 Demineralized Whey Powder
In the applications of whey powder, the minerals
can interfere with the taste. The production
of demineralized whey powder proceeds via ion
exchange or, preferentially, electrodialysis (1.5–
4.5V/cell; current density 5–20 mA/cm 2 membrane
area, Fig. 10.31). The course of demineralization
is shown in Fig. 10.32.
Fig. 10.32. Whey demineralization. Ions of a chloride,
b sodium, c potassium, d calcium, e phosphate, f lactate,
g citrate, and h magnesium
10.2.10.3 Partially Desugared Whey Protein
Concentrates
In the ultrafiltration of whey, protein concentrates
depleted of lactose to various extents are
obtained, depending on the number of stages
and amount of wash water. Another, less gentle
method involves the heating of whey (95 ◦ C,
3–4 min) by direct steam injection, followed
by precipitation of the denatured proteins at
pH 4.5, separation in a sedimentation centrifuge
(2000–4000 min −1 ), and drying.