2009_Book_FoodChemistry

524 10 Milk and Dairy Products
fermentation) and Lactobacillus brevis, L. casei,
Leuconostoc mesenteroides, Streptococcus durans,
Saccharomyces delbrueckii, S. cerevisiae
and Acetobacter aceti. The kefir bacillus causes
a buildup of “kefir grains”, which resemble
cauliflower heads when wet and brownish seeds
when dry, and are particles of clotted milk plus
the kefir organisms. Their addition to fluid milk
produces kefir. Kumiss is made of mare’s or
goat’s milk fermented by the obligatory pure
kumiss culture.
Both dairy beverages are indigenous to the Caucasus
and steppes of Turkestan. Kefir contains
lactic acid (0.5–1.0%), noticeable amounts of alcohol
(0.5–2.0%) and carbon dioxide, and some
products of casein degradation resulting from
proteolytic action of yeast. Normal kumiss contains
1.0–3.0% of alcohol. The production is
similar to that of yoghurt.
10.2.1.4 Taette Milk
Taette (Lapp’s milk) is a specially fermented, sour
cow’s milk product consumed in Sweden, Norway
and Finland. Its thread-like, viscous structure
is due to the formation of slimy substances at the
low fermentation temperatures used. Mesophilic
microorganisms (Lactococcus and Leuconostoc
spp.) are involved in this process.
Fat droplets accumulate during whipping on the
surface of large air bubbles which form the froth.
An increased build-up of smaller bubbles tears
apart the membrane of the droplet and enlarges
the fat interphase area, thus resulting in gel setting
of the lamella separating the individual air
bubbles. Sour cream is the product of progressive
lactic acid fermentation of cream.
10.2.3 Butter
Butter is a water-in-oil emulsion (w/o emulsion)
made from cream by phase inversion occurring
in the butter-making process. According to its
manufacturing process, three types exist:
• Butter from sour cream (cultured-cream butter).
• Butter from nonsoured, sweet cream (sweet
cream butter).
• Butter from sweet cream, which is soured in
a subsequent step (soured butter).
Butter contains 81–85% fat, 14–16% water, 0.5–
4.0% fat-free solids and 1.2% NaCl in the case
of salted butter. The composition generally must
meet legal standards. Butter is an emulsion with
a continuous phase of liquid milk fat in which
are trapped crystallized fat grains, water droplets
10.2.2 Cream
Milk is practically completely defatted (remaining
fat content 0.03–0.06%) in hermetic,
self-cleaning or hermetic/self-cleaning creaming
separators. The cream products are subsequently
standardized by back-mixing. Whipping cream
contains at least 30% milk fat, coffee cream at
least 10% and butter cream 25–82%. Cream is
utilized in many ways, either by direct consumption
or for production of butter and ice creams.
Whippability and stability of the whipped foam
products are necessary whipping cream properties.
For the best quality cream, a volume increase
of at least 80% is expected and a standard
cone with 100 g load must penetrate 3 cm deep in
>10 s. No serum separation should occur at 18 ◦ C
after 1 h.
Fig. 10.22. Freeze-fracture micrograph of butter (F: fat
globule, W: water droplet; according to Juriaanse and
Heertje, 1988)