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Lactose Formula

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  • Last Updated : 18 Nov, 2022
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Lactose is a type of carbohydrate that is also called milk sugar and lactobiose. It is a disaccharide that is synthesized from galactose and glucose subunits. The “lactase” enzyme breaks lactose into glucose and galactose when it is absorbed in the intestine. It is used in the food industry, bacterial identification, and pharmaceutical industry, and is also used as a nutrient, and cutting agent. It is an essential carbohydrate for infants. 

What is Lactose Formula?

The molecular formula of lactose is C12H22O11, i.e., it is composed of 12 carbon atoms, 22 hydrogen atoms, and 11 oxygen atoms. It is a white solid that has a mild sweet taste. It is soluble in water and is a non-hygroscopic solid. Lactose was first discovered by Italian physician Fabrizio Bartoletti. Milk contains around 2-8% lactose (by mass). Lactose is found in the mammary glands of all mammals, and a very small amount of lactose can be found in dairy products like yogurt and cheese. It is less sweet when compared to sucrose. 

Structure Of Lactose

Lactose is a disaccharide sugar that is formed by the β-1→4 glycosidic linkage of β-D-glucose and β-D-galactose.

Structure Of Lactose

 

Preparation of Lactose

  • Lactose can be produced from β-D-glucose and β-D-galactose.
Preparation of Lactose

 

  • Industrially, lactose is prepared from whey permeate, where whey is comprised of 6.5% solids, of which 4.8% is lactose, which is crystallized and purified further. It can also be extracted by diluting whey with ethanol.

Physical Properties of Lactose

Chemical formula  C12H22O11 
Molar mass 342.297 g/mol 
Appearance White solid
Odor Odorless
Taste Sweet
Density 1.525 g/cm3
Melting point 252°C (anhydrous)
202°C (monohydrate) 
Solubility Soluble in water, very slightly soluble in alcohol, insoluble in ether and chloroform
Hydrogen bond donor count  8
Hydrogen bond acceptor count  11
Rotatable bond count 8
Complexity 367
Flash point 357.8 °C

Chemical Properties of Lactose

  • Lactose on hydrolysis with 2% H2SO4 yields 1 mole of D-glucose and 1 mole of D-galactose.

C12H22O11 + H2O → C6H12O6 (glucose) + C6H12O6 (galactose)

  • Polyhydric alcohol named lactitol is produced by the catalytic hydrogenation of lactose. Lactose undergoes hydrogenation in the presence of a Raney-Nickel catalyst, resulting in the formation of lactitol.
  • Lactose is isomerized in an alkaline solution to produce Lactulose.
  • The molar mass of Lactose is 342.297 g/mol.

Uses of Lactose

Lactose has various uses some of which are:

  • Lactose is used as a nutrient in preparing modified milk and is also added to infants’ food to match the composition of human milk.
  • It helps the body to absorb calcium and a variety of other minerals, like magnesium, copper, and zinc.
  • Because of its physical and functional properties, lactose is added as an ingredient in pharmaceutical products like an excipient and diluent for tablets and capsules.
  • It is used in the food industry as a flavoring agent.
  • It is used in baked goods and also in fermentation for the production of cheese, yogurt, and sour milk.
  • It is also used as a chromatographic adsorbent in analytical chemistry.

Side Effects

Side Effects of Lactose are:

  • Lactose cannot be digested by people who are intolerant to lactose. 
  • Intake of lactose-rich milk can lead to breast and ovarian cancer. 
  • Intake of lactose-rich milk can also increase the risk of a heart attack as milk having a high concentration of lactose is rich in fat and cholesterol.

FAQs on Lactose Formula

Question 1: What is lactose?

Answer:

Lactose is a disaccharide that is also called milk sugar or lactobiose. It is a type of carbohydrate whose molecular formula is C12H22O11. It is composed of 12 carbon atoms, 22 hydrogen atoms, and 11 oxygen atoms. It is synthesized from galactose and glucose subunits.

Question 2: Mention some properties of lactose.

Answer:

Lactose is a disaccharide sugar whose molecular formula is C12H22O11. It is a white solid that has a mild sweet taste. It is soluble in water and is a non-hygroscopic solid. The molar mass of lactose is 342.297 g/mol and its density is 1.525 g/cm3. It can be detected with the help of Woehlk and Fearon tests.

Question 3: Calculate the molecular weight of lactose.

Answer:

We know that the chemical formula of lactose is C12H22O11.

The atomic mass of a hydrogen atom = 1.00794
The atomic mass of a carbon atom = 12.0107
The atomic mass of an oxygen atom = 15.9994

Now, 
Molar of Lactose = 12 × 12.0107 + 22 × 1.00794 + 11 × 15.9994
                           = 144.1284 + 22.17468 + 175.9934
                           = 342.29648 g/mol

So, the molar mass of Lactose is 342.29648 g/mol.

Question 4: Write the reaction of the hydrolysis of lactose.

Answer:

Lactose on hydrolysis with 2% H2SO4 yields 1 mole of D-glucose and 1 mole of D-galactose.

C12H22O11 + H2O → C6H12O6 (glucose) + C6H12O6 (galactose)

Question 5: What are the applications of lactose?

Answer:

Lactose is used as a nutrient in preparing modified milk and is also added to infants’ food to match the composition of human milk. It is used in baked goods and also in fermentation for the production of cheese, yogurt, and sour milk. It is also used as a chromatographic adsorbent in analytical chemistry.

Question 6: How is Lactitol prepared from Lactose?

Answer:

Polyhydric alcohol named lactitol is produced by the catalytic hydrogenation of lactose. Lactose undergoes hydrogenation in the presence of a Raney-Nickel catalyst, which results in the formation of lactitol.

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