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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.

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