2009_Book_FoodChemistry

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