Lactose is a sugar present in milk. It is one of the important classes of biomolecules is carbohydrates. These biomolecules have a major role in daily life by providing three requirements. These requirements are food (starch), shelter (cellulose) and cloth (cellulose).


Introduction of Lactose

Lactose is basically a disaccharide.  Lactose crystals have water of crystallization, because of which molecular mass of lactose becomes 360.3 g/mol compared to 342.3 g/mol of anhydrous lactose. It is slightly soluble in ethanol but quite soluble in water. When lactose monohydrate is heated up to 418 K, this results in the removal of one molecule of water, this removal is from lactose anhydrous.

Lactose is a sugar that is composed of galactose and glucose subunits. The molecular formula of lactose is \(C_{12}H_{22}O_{11}\). Lactose makes up around 2 per cent to 8 per cent of milk by weight. The name comes from the word lac means milk and the suffix -ose used to name sugars. It is white and water-soluble. Lactose is a non-hygroscopic solid with a mild sweet taste. It is in use in many of the food industries.

Biological Properties of Lactose

  • The sweetness of lactose is 0.2 to 0.4. This value is relative to 1.0 for sucrose. For comparison, the sweetness of glucose is 0.6 to 0.7, fructose is 1.3, galactose is 0.5 to 0.7, maltose is 0.4 to 0.5, sorbose is 0.4, and xylose is 0.6 to 0.7.
  • When lactose is digested in the small intestine, the caloric value of lactose is 4 kcal/g. Thou lactose is not always fully digested in the small intestine. Depending on the ingested dose, combination with meals and lactase activity in the intestines, the caloric value of lactose ranges from 2 to 4 kcal/g. Undigested lactose acts as dietary fibre. It has positive effects on the absorption of minerals like calcium and magnesium.
  • The glycemic index of lactose is 46 to 65.
  • Lactose has relatively low cariogenicity among sugars. This is because lactose is not a substrate for dental plaque formation and is not rapidly fermented by oral bacteria. The buffering capacity of milk reduces the cariogenicity of lactose.

FAQs on Lactose

Question 1: What are the applications of lactose?

Answer: The mild flavour of lactose and easy handling properties of lactose have led to its use as a carrier and stabiliser of aromas products in pharmacy. Lactose is not directly added to many foods as its solubility is less than that of other sugars that are commonly used in food. Infant formula is a notable exception, where the addition of lactose is important to match the composition of human milk.

Lactose is not fermented by most yeast during brewing, so it is an advantage. For example, lactose can be used to sweeten the stout beer. The resulting beer is usually a milk stout or a cream stout.

Yeast belonging to the genus Kluyveromyces have an industrial application because they are capable of fermenting lactose for ethanol production. Surplus lactose from the whey by-product of dairy operations is a source of alternative energy.

The significant and important use of lactose is in the pharmaceutical industry. Lactose is added to tablet and capsule drug products as an ingredient due to its physical and functional properties. For similar reasons, lactose can also be used to dilute illicit drugs like cocaine or heroin.

Question 2: What do you mean by lactose intolerance?

Answer: Lactose intolerance relates to a body that cannot digest lactose that is found in milk and other dairy products. When lactose travels through the colon i.e., large intestine without being properly digested, it creates uncomfortable symptoms like belly pain, bloat, and gas. People with lactose intolerance cannot digest milk or any other dairy products. Lactose intolerance is usually found in adults. It is a big challenge for people who are lactose-intolerant is to learn what to eat to avoid discomfort and also to get enough calcium for healthy bones.

Lactose intolerance is when the small intestine does not make enzymes that are lactose so the body itself requires lactose to break down or digest lactose. Some premature babies have temporary lactose intolerance as they are not yet capable of producing lactose. After a baby starts to produce lactose, the condition goes away automatically.

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