Food Chemistry

10.2 Dairy Products 525

Fig. 10.23.Crystalline shell of a fat grain, as found in
butter, which was obtained by eliminating the included
oil; (according toJuriaanseandHeertje, 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

Fig. 10.24.Production of butter

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 process-

ing steps involved in butter making is given in

Fig. 10.24.

10.2.3.1 Cream Separation and Treatment

Cream is separated from whole milk by high-

efficiency separators (cf. 10.1.3.2 and 10.2.2).

The cream, depending on the subsequent churn-

ing process, should contain 25–82% milk fat.

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

Cream ripening and souring are the most import-

ant steps in the production of sour cream butter.

The process is performed in a cream ripener or

vat, with suitable mixing and temperature con-

trol. Soon after the cream has filled the ripener,

a “starter culture” is added, followed by incu-

bation 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 (primarilyLactococ-

cus lactis subsp. lactis, Lactococus lactis subsp.

cremoris, Lactococus lactis subsp. diacetylactis

andLactococcus lactis subsp. cremoris bv. citro-

vorum). The subsequent ripening at 8–19◦Cpro-

ceeds 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 low-

melting milk fat fraction. As a result, a mixture

of crystalline higher-melting TG and liquid low-

melting 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

Churning is essentially strong mechanical cream

shearing which tears the membranes of the