Nutritive and Health Attributes of Dairy Ingredients 401product of attack by the natural proteolytic
enzyme plasmin. The N - terminal residue is
the proteose - peptone fraction. These hydro-
lysis products of β - casein occur at a range of
3% to 10% of the total casein content of milk.
The stage of lactation and health status of the
cow affect their concentration.Biologically Active Peptides Derived
from Casein
Peptides derived from caseins are biologi-
cally active and display signifi cant extra
nutritional attributes for maintaining nor-
malcy of physiological functions in human
subjects.
Table 16.14 lists bio - active peptides origi-
nating from caseins.caseins, which impacts their nutritional defi -
ciency. In contrast, the content of the essen-
tial amino acid lysine is high. In the human
diet, the high lysine content is helpful in
complementing and balancing the low - lysine
plant proteins. The ε - amino group of lysine
present in caseins interacts with the aldehyde
group of lactose at elevated temperatures,
leading to the formation of brown pigments.
This also explains browning of heat - sterilized
milk and nonfat dry milk during extended
storage. The high proline content of caseins
results in low α - helix and β - sheet in their
secondary structure, giving them the ability
for more proteolytic degradation and
enhanced digestion (Otter, 2003 ).
Among the minor milk caseins, γ - casein
is the C - terminal fragment of β - casein, a
Table 16.13. Bioactivity of milk proteins.
Protein Physiological effect
Caseins Precursors of bioactive peptides; calcium and phosphorus carrier.
Bioactive peptides of caseins such as casomorphins lower gut motility
and gastric emptying rate, enhance uptake of amino acids by intestinal
epithelial cells, and enhance immune response and phagocytic activity
Casokinins (ACE - I) enhance blood fl ow to intestinal epithelium
Isracidin, casecidins, and kappacin exhibit bactericidal activity against
pathogenic organisms. κ - casein enhances the growth of bifi dobacteria
in the gastrointestinal tract
Whey proteins Confer passive immunity for disease prevention, reduce risk of heart
disease and lower blood pressure, anti - viral and anti - cancer activity,
control of gut microfl ora, control of cellular glutathione level
β - lactoglobulin Binds zinc, calcium, and fat - soluble vitamins
The branched chain amino acids enhance the immune system
α - lactalbumin Lactose synthesis in mammary gland, anti - carcinogenic and immune
enhancing effects
May be associated with stress reduction, increase serotonin production in
brain, improve mood, and decrease cortisol level
Immunoglobulins A, M, G^1 , G^2 Antibodies against diarrhea and GI tract disturbances
Support passive immune function
Bovine serum albumin Antioxidant and anti - mutagenic
Binds free fatty acids and pro - oxidant transition metals
Lactoferrin Bacterial anti - toxin binding, antibacterial, anti - viral, immune modulating,
anti - infl ammatory, anti - thrombic activity, anti - carcinogenic, antioxidant,
iron absorption
Enhances proliferation of intestinal epithelial cells, humoral immune
response, and growth of bifi dobacteria in gastrointestinal tract
Lactoperoxidase Antimicrobial, antioxidant, immune enhancing properties
Lysozyme Antimicrobial, synergistic with immunoglobulins and lactoferrinAdapted from Chandan (1999) , Gobbetti, et al. (2007) , Harper (2000) , Hoolihan (2004)