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10.2 Dairy Products 525

extent of fluid fat inclusion into the solidified “fat

grains”. Figure 10.23 shows the crystalline shell

of a cut fat grain, from which the liquid fat was

removed during preparation.

A general idea of the most important processing

steps involved in butter making is given in

Fig. 10.24.

10.2.3.1 Cream Separation and Treatment

Fig. 10.23. Crystalline shell of a fat grain, as found in

butter, which was obtained by eliminating the included

oil; (according to Juriaanse and Heertje, 1988)

and air bubbles. A freeze-fracture micrograph

of butter showing the continuous fat phase with

included fat globules and water droplets is shown

in Fig. 10.22. Butter consistency is determined

by the ratio of free fluid fat to that of solidified

fat. Due to seasonal variations in the unsaturated

fatty acid content of milk fat, the solid/fluid fat

ratio fluctuates at 24 ◦ C between 1.0 in summer

and 1.5 in winter. Equalization of these ratios

is achieved by a preliminary cream-tempering

step in a cream-ripening process, then churning

and kneading the cream, which influences the

Cream is separated from whole milk by highefficiency

separators (cf. 10.1.3.2 and 10.2.2).

The cream, depending on the subsequent churning

process, should contain 25–82% milk fat.

The cream is then pasteurized at 90–110 ◦ C.

Cream ripening and souring are the most important

steps in the production of sour cream butter.

The process is performed in a cream ripener or

vat, with suitable mixing and temperature control.

Soon after the cream has filled the ripener,

a “starter culture” is added, followed by incubation

for 12–24 h at 8–19 ◦ C. The pH falls to

4.6–5.0. The “starter culture” consists of various

strains of lactic acid bacteria (primarily Lactococcus

lactis subsp. lactis, Lactococus lactis subsp.

cremoris, Lactococus lactis subsp. diacetylactis

and Lactococcus lactis subsp. cremoris bv. citrovorum).

The subsequent ripening at 8–19 ◦ Cproceeds

for 12 to 24 h.

The formation of fat crystals can be influenced

by suitable temperature control during the cream

ripening process. Consequently, the consistency

of the butter can be influenced and corrected. The

souring step is omitted in the production of sweet

cream butter. The pasteurized cream is cooled for

about 3 h at 4–6 ◦ C to induce the crystallization

of fat in the fat globules. It is then stored for

about 5 h at a temperature which is 1–2 ◦ C higher

than the melting range (17–19 ◦ C) of the lowmelting

milk fat fraction. As a result, a mixture

of crystalline higher-melting TG and liquid lowmelting

TG is formed, which is easy to spread.

The cream then ripens for at least 10 h at 10–

14 ◦ C.

10.2.3.2 Churning

Fig. 10.24. Production of butter

Churning is essentially strong mechanical cream

shearing which tears the membranes of the

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