Chemical and Functional Properties of Food Saccharides

© 2004 by CRC Press LLC
GAGs also influence functional properties of collagen. For instance, the presence
of 30% chondroitin sulfates shifts the shrinkage temperature of collagen by 10°C.
The type and number of associated PGs is essential for resistance of collagen to
enzymatic degradation, which results in an increase in collagen solubility. An
increase in beef tenderness on cold ageing is accompanied by increase in the activity
of glucuoronidase. Structure of PGs and their ability of holding water is critical for
the resistance of cartilage to deformation on stretching and compression.
Transformations of GAGs in animal organisms are influenced by the pituitary
gland, thyroid, and testes hormones. Growth hormones induce the synthesis of
GAGs, increase the number of mast cells in connective tissue, and stimulate the
activity of hyaluronidase. Testosterone and estrogens stimulate synthesis of HA and
chondroitin sulfates. Thyroxine and triiodothyronine, as well as glucocorticoids,
inhibit GAG metabolism.
16.3.3 UTILIZATION OF GLUCOSYLAMINOGLYCANS
Ability of GAGs to hold water and salts and their interactions with protein can be
useful in modifications of rheology of foodstuffs and in cosmetics. Effect of acidic
GAGs on the viscosity and emulsifying properties can be applied in stabilization of
meat batter.
GAGs can be helpful in reconstitution of collagen in vitro. In the presence of
GAGs (DS, HA) in aqueous solution, collagen fibrils are formed even from fractions
of soluble collagen that normally do not exhibit any tendency for reconstitution.
The pharmaceutical industry utilizes HA sodium salt in manufacturing medicine
for ophtalmological surgery of cataract, cornea transplantation, therapy of glaucoma,
and damage of bulbus oculi. HA is injected to joints in case of arthritis.
16.4 GLYCOPROTEINS
Most plasma proteins, particularly blood-group specific substances, many milk and
egg proteins, mucins, connective tissue components, some hormones, and many
enzymes are glycoproteins (GPs). GPs are found in all extracellular biological fluids.
Several integral proteins of cells and intracellular plasma membranes contain an
oligosaccharide component. The saccharide portion is 5 to 10% of the mass of GPs.
Polysaccharide chains with GPs have up to 15 monosaccharide units.
GPs contain various sugar residues linked to one another by various glycosidic
bonds. Usually, the carbohydrate component of GPs, an oligosaccharide, is attached
to the oxygen atom of the side chain of either serine or threonine, and optionally
forms an N-glycosidic linkage with the nitrogen atom of the side chain of aspartic
acid residues.
GP oligosacharides linked through the N-glycosidic bond contain a common
pentasaccharide core composed of three molecules of mannose (Man) and two Nacetyloglucosylamine
(GlcNAc) molecules. Subsequent saccharides are variously
bound to this core, which is responsible for a wide variety of GPs oligosacharides.
In oligosaccharides rich in Man, the Man residues are attached to the oligosaccharide
core. In complex oligosaccharides, various combinations of GlcNAc, galactose (Gal),