Volume 22 • Issue 05 • 2018
the predominant glycolipid in the glycosylation
of complex molecules such as myelin in the Leloir
pathway. As a result Galactose is often referred to
as the “brain sugar”. Galactose is also a component
of the molecules present on blood cells that
determine the ABO blood types.
There is evidence that it may play a role in the
absorption of minerals such as calcium, copper
and zinc. However, the suspicion exists that
osteoporosis in Lactose-intolerant individuals
may be the result of avoidance of dairy products
in their diet, rather than as a lack of Lactose.
If Lactose is not digested in the small intestine
it may be used as a prebiotic by certain large
intestine bacteria. Most notably it promotes the
growth of bifidobacteria which may play a life-
long role in countering the ageing-associated
decline of some immune functions.
LACTOSE HAS MANY USES
Despite its significant commercial value, the
majority of milk processors do not have the ability
to “harvest” Lactose. As a result, dairy farmers are
not paid a premium based on their Lactose levels,
as is the case for protein and butterfat levels.
Lactose plays a crucial role in determining milk
volume and has significant value in its own right.
During the cheese and butter manufacturing
process lactose remains in the whey fraction.
Whey acts as the primary commercial source
of lactose through a process of crystalizing an
oversaturated whey solution.
Lactose has many commercial uses, especially in
the food and pharmaceutical industry:
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It is used when excessive sweetness is
undesirable. Especially in milk formulas
for babies where it reduces the sensation
of appetite and prevents cravings for sweet
foods and overeating. Lactose is also less
cariogenic (causing less tooth decay) than
other sugars.
Reducing the sugar content in foodstuffs can
be problematic since sugar affects the flavour,
colour and texture of several foods. Especially
in the confectionary industry. Lactose is
commonly used as a substitute because of
its low sweetness and excellent bulking
properties.
Because lactose has low sweetness and low
water solubility it is commonly used as an
excipient in the pharmaceutical industry
to coat tablets. Estimates puts its use as
high as 70%. It also has excellent tablet
forming qualities and is used as a bulking
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agent. Lactose in tablets is only present
in milligrams and therefor not present in
sufficient quantities to cause symptoms in
lactose -intolerant individuals.
Lactose is sometimes added to cow’s milk to
simulate the high lactose content of human
breastmilk.
Lactose is sprayed onto silage to increase acid
formation during the fermentation process.
Lactose can also be used to produce ethanol.
LACTOSE SYNTHESIS
Lactose synthesis is initiated in the secretory
vesicles of the Golgi apparatus. Glucose is
converted to UDP- Galactose and through the
action of the enzyme lactose-synthetase a Glucose
and UDP-galactose combine to form a Lactose
molecule. The milk protein, beta-lactalbumin,
must be present for Glucose and UDP-galactose to
combine. As a result, beta-lactalbumin is a major
limiting factor in the production of Lactose and
hence milk volume. As the Lactose is produced,
water flows into the vesicles through osmosis
to try and dilute the lactose and maintain
equilibrium. Lactose accounts for approximately
50% of the osmotic pressure of milk. The
balance is made up by ions, citrate and proteins.
Consequently, the vesicles swell, move to the cell
membrane and break open to release the milk
into the lumen of the milk ducts.
The milk ducts are impermeable to the
constituents of milk. No re-absorption of milk
constituents or water takes place in the milk
ducts. The ducts are merely conduits and storage
vessels for the milk to flow to the teats until such
a time as the milk is extracted.
rBST increases the availability of Glucose to the
alveolar cells by increasing the blood flow to the
udder. As a result, more Lactose is produced and
through the osmotic effect of Lactose more water
is drawn into milk production and increases the
volume of milk produced. The increased volume
of milk is proportional to the levels of Lactose,
therefor there will be no change in the milk
Lactose concentration.
Serotonin is also produced in mammary tissue
and is under partial control of prolactin. Delayed
milking will increase serotonin levels which
down-regulates the synthesis of Lactose, which
in turn will reduce milk production. Milk yield
can thus be increased through more frequent
milking or by increasing the photoperiod. Once
again, the Lactose remains proportional to the
milk production and therefor there is no change
in the lactose concentration in the milk
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