324 Chapter 12
system in newborn infants. Furthermore,
immunopeptides formed during milk fermen-
tation may contribute to the anti - tumor effect
of fermented milk.Casein Hydrolyzates
Hydrolyzed casein is a rich source of pep-
tides, many of which have physiological
effects. The properties of α - casein hydroly-
sates differ, depending upon the enzymes
used to digest them. Trypsin hydrolysis of
α - casein promotes antibody formation and
phagocytosis (the engulfi ng of the cell wall
of external cell material, such as bacteria)
and reduces the severity of infections. Resi-
dues 90 to 96 (Arg - Tyr - Leu - Gly - Tyr - Leu -
Glu) and 90 to 95 (Arg - Tyr - Leu - Gly - Tyr - Leu)
of α - casein have been shown to have opioid
properties, increasing the body ’ s natural
killer cells ’ (lymphocytes) responses and
boosting the number of white blood cells.
Beta - casein is the source of numerous bio-
active peptides. Residues 63 to 68 (Pro - Gly -
Pro - Ile - Pr - Asn) and 191 to 193 (Leu - Leu - Tyr)
of β - casein promote antibody formation and
phagocytosis. Other peptides derived from
β - casein have anti - hypertensive activity, pro-
mote mineral absorption, or have an opiate -
like effect ( β - casomorphins). Furthermore,
these peptides are considered to be immune
suppressive when taken orally. Because
immunosuppresion prevents the body from
rejecting organ and bone marrow transplants,
or is used to treat auto - immune diseases such
as Crohn ’ s disease, work within this fi eld
could open up a new market for β - casein
peptides.
Similar to the other casein peptides, the
digestion of κ - casein results in several pep-
tides, which adjust or change the immuno-
modulatory responses of the body. The
κ - casein peptide Phe - Phe - Ser - Asp - Lys pro-
motes antibody formation and phagocytosis,
while the κ - casein peptide Tyr - Gly increases
the generation of lymphocytes in the human
body.forms phenyl lactate, benzaldehyde, phenyl-
acetate, and phenylethanol. These are a few
examples of fl avor - impact compounds
present in cheese; they refl ect the chemical
complexity of cheese fl avor.
Ingredients Involving Proteolysis
and Lipolysis
Proteolysis
Proteolysis of casein and whey proteins leads
to products called casein hydrolyzate and
whey protein hydrolyzate. For each type of
protein, various degrees of hydrolysis can be
achieved. Casein hydrolyzates are often bitter
due to the preponderance of hydrophobic
amino acids. Whey protein hydrolyzates are
non - bitter but astringent.
Milk and whey peptides are latent until
released and activated, e.g., from digestion or
milk fermentation. Once activated, these pep-
tides have many bioactive functions, all of
which relate to general health conditions or
reducing the risk of certain chronic diseases.
Some examples of the physiological effects
of peptides are given below. These proteins
are subject to considerable research world-
wide. The best data so far indicate that ACE -
inhibitory peptides limit the formation of
angiotensin II, a potent chemical that causes
the muscles surrounding the blood vessels
to contract and thereby increasing blood
pressure.
Recent studies have indicated that dairy
peptides are opioid peptides and may play an
active role in the nervous system. Once
absorbed into blood, these peptides can travel
to the brain and other organs and cause phar-
macological properties similar to opium and
morphine. This may be why newborn infants
generally become calm and sleepy after
drinking milk. It also has been suggested that
these peptides may alleviate allergic reac-
tions in humans and enhance mucosal immu-
nity in the gastrointestinal tract; thus, peptides
may regulate the development of the immune