Milk lactose – main roles in human body

Milk is an emulsion produced by mammary glands which characterise with white colour, mild taste and flavour.

The major constituent of milk is water, but milk contains varying levels of lipids, proteins, and carbohydrates which are synthesized within with mammal gland. Their composition is influenced by animal species, environmental conditions, nutrition of animals, their lactation state and others.

Lactose is the principal carbohydrate found in milk. It is virtually unique to milk, having been found elsewhere only in fruits of certain members of the Sapotaceae. Lactose is consumed through milk and other unfermented dairy products, such as ice cream.

Disaccharides lactose in milk imparts sweet profile and human milk has a major concentration of lactose (7.4%) compared to milk of other species. The main role of lactose includes:
*It provides galactose for the synthesis of the nerve structures of the growing infant
*In the intestine, it gets metabolized to lactic acid which eliminates harmful bacteria.

Lactase is a membrane-bound enzyme located in the brush border epithelial cells of the small intestine. Once lactose reaching the small intestine, where the hydrolytic enzyme lactase (β-galactosidase) is located, lactase catalyzes the hydrolysis of lactose into its constituent monosaccharides (glucose and galactose). Only monosaccharides among the carbohydrates are absorbed from the intestines.

Lactose accounts for ~30% of the caloric value of whole milk. Lactose is an important energy source and sometimes it is referred to simply as milk sugar, as it is present in high percentages in milk. Lactose-intolerance individuals have a lactase deficiency; therefore, lactose is not completely catabolized.
Milk lactose – main roles in human body

Lactose (milk sugar)

Lactose (milk sugar)
The characteristics carbohydrate of milk is lactose, a disaccharides composed of one molecule of D-glucose and one of D-galactose, which is synthesized in the mammary gland.

The lactose content of cow’s milk is fairly constant, ranging from 4 to 5%. In contrast, milk from cows with mastitis have lactose contents as low as 2.7%.

The more lactose a milk contains, the sweeter its taste. Cow’s milk, with a mean lactose content of 4.6%, tastes faintly sweet.

It is interesting to note that although sweet (nonacid), whey has about the same concentration of lactose as the milk from which it is made, it is much sweeter than milk, due to undoubtedly to the removal of casein.

Lactose in milk is readily fermented by a number of bacteria to yield lactic acid. The changes that accompany the conversion of lactose into lactic acid is associated with the souring of milk. The odor of sour milk is not due to lactic acid but to other volatile products formed during fermentation.

Lactose, in common with other disaccharides, must be hydrolyzed by specific enzymes in the digestive tract into monosaccharide before absorption and utilization by the body.

Lactase the enzyme responsible for the hydrolysis of lactose to D-glucose and D-galactose occurs in the intestinal mucosa of mammals. When lactose intake exceeds the amount that lactose can hydrolyze, symptoms of lactose intolerance (flatulence, cramps, and diarrhea) may ensue.
Lactose (milk sugar)