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 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)
