404 Chapter 16
It is an excellent source of essential amino
acids such as tryptophan and cysteine.
Tryptophan regulates appetite, sleep - waking
rhythm, and pain perception, and cysteine is
important in functions of – SH compounds.
Immunoglobulins
There are fi ve major classes of immunolo-
globulins: IgA, IgD, IgE, IgG, and IgM.
Their concentration is very high (100 g/L) in
the fi rst two to three milkings after the birth
of a calf birth, but their concentration falls
to 0.6 to 1 g/L soon after. Immunoglobulins
are antibodies synthesized in response to
stimulation by specifi c antigens. These offer
nonspecifi c humoral response to Gram -
negative enteric and aerobic bacteria.
Accordingly, they provide passive immune
protection to the newly born calf. The basic
structure of all immunoglobulins is similar:
two identical light chains (23,000 Da) and
two identical heavy chains (53,000 Da) joined
by disulfi de bonds. The complete molecule
has a molecular weight of about 180,000 Da.
The antigenic sites are located at the – NH 2
terminal of the respective chain. Of the fi ve
immunoglobulin classes, IgG is the predomi-
nant fraction of milk, comprising about 90%
of the total colostral immunoglobulins.
Relatively smaller concentrations of IgM and
IgA also are present in progressively decreas-
ing amounts.
The immunoglobulins of milk are impor-
tant for imparting immune defense for the
host. IgG1 is a major component. Other frac-
tions are IgG2, IgA, and IgM, all of which
provide passive immunity.
A number of colostrum products are mar-
keted as functional ingredients for foods.
Colostrum contains several functional con-
stituents, including antibodies, lactoferrin,
lactoperoxidase, cytokines, and growth
factors. The antibodies act as antimicrobial
agents against infection from rotavirus
(which causes diarrhea), Escherichia coli
(which causes food poisoning ), Candida
albicans (which causes yeast infections),
Streptococcus mutans (which causes dental
caries), Clostridium diffi cile (which causes
antibiotic - associated diarrhea), Cryptospo-
rium parvum (which causes food poisoning),
and Helicobacter pylori (which causes ulcers
and gastritis). Colostrum stimulates the active
immune system by enhancing the activity of
natural killer cells and phagocytes. Colostrum
powder is manufactured by a special drying
process to ensure activity. Milk protein con-
centrate prepared from the milk of hyper -
immunized cows is said to relieve the joint
pain of arthritis by complementing the body ’ s
natural anti - infl ammatory substances.Bovine Serum Albumin
As the name indicates, bovine serum albumin
originates from blood. It spills into milk
during synthesis in the udder. It is a large
molecule with a binding ability for fatty acids
and metals.Lactoferrin
Lactoferrin, also known as lactotransferrin, is
a glycoprotein that displays a strong ten-
dency to bind ionic iron due to the presence
of two metal binding sites. The average lac-
toferrin content for cow milk is 0.32 mg/ml.
The molecular weight of lactoferrin varies
between 73,700 and 74,000 Da. Lactoferrin
displays a very strong chelating tendency for
ionic iron and forms a salmon - red pigment.
It is a single peptide chain with two lobes,
each of which is capable of binding iron.
The iron - free form of lactoferrin is known
as apolactotransferrin, which is colorless.
Lactoferrin displays activity against several
Gram - positive and Gram - negative bacteria,
yeasts, fungi, and viruses. It shows a particu-
larly strong inhibitory effect toward Gram -
negative enteropathogenic bacteria by virtue
of its ability to bind free ionic iron, which is
essentially required for the growth of entero-
pathogenic microorganisms. Thus, lactofer-
rin plays a role in non - specifi c defense of the