Skip to Content


« Back to Glossary Index

**1. Chemical Properties and Structure of Lactose:**
– Lactose is a disaccharide composed of glucose and galactose.
– Its systematic name is β-galactopyranosyl-(1→4)-glucose.
– Lactose is less sweet than sucrose and is soluble in water.
– It undergoes hydrolysis to break down into its monosaccharide components.
– The enzyme lactase is required to break down lactose in the digestive system.

**2. Occurrence, Isolation, and Industrial Uses of Lactose:**
– Lactose makes up about 2–8% of milk by weight.
– Several million tons of lactose are produced annually as a by-product of the dairy industry.
– Whey, containing 4.8% lactose, is purified by crystallisation.
– Lactose is used in the pharmaceutical industry as a filler in tablets.
– It is also utilized in the food industry for its sweetening properties and in the production of certain cheeses.

**3. Metabolism and Health Effects of Lactose:**
– Infant mammals produce lactase to digest lactose in milk.
– Lactase production decreases with maturity due to weaning.
– Over 70% of western Europeans can digest lactose as adults.
– Lactose intolerance can lead to gastrointestinal symptoms like bloating and diarrhea.
– Lactose-free products are available for those with lactose intolerance.

**4. Biological Properties and Applications of Lactose:**
– Lactose has a sweetness index of 0.2 to 0.4 and a caloric value of 4 kcal/g when fully digested.
– Undigested lactose acts as dietary fiber and aids in mineral absorption.
– Lactose is used as a carrier and stabilizer for aromas and pharmaceutical products.
– It is essential in infant formula to match human milk composition.
– Lactose is used in tablet and capsule drug products for its properties.

**5. Sources, Historical Significance, and Detection Reactions of Lactose:**
– Sources of lactose include dairy products, processed foods, medications, and supplements.
– Lactose was first isolated from milk in the 18th century.
– Scientists like Carl Wilhelm Scheele and Emil Fischer made significant contributions to understanding lactose.
– The configuration of glucose and galactose was determined by Fischer.
– Detection reactions for lactose include the Woehlk and Fearons test.

Lactose (Wikipedia)

Lactose, or milk sugar, is a disaccharide sugar composed of galactose and glucose subunits and has the molecular formula C12H22O11. Lactose makes up around 2–8% of milk (by mass). The name comes from lact (gen. lactis), the Latin word for milk, plus the suffix -ose used to name sugars. The compound is a white, water-soluble, non-hygroscopic solid with a mildly sweet taste. It is used in the food industry.

IUPAC name
Systematic IUPAC name
Other names
Milk sugar
3D model (JSmol)
ECHA InfoCard 100.000.509 Edit this at Wikidata
EC Number
  • 200-559-2
  • InChI=1S/C12H22O11/c13-1-3-5(15)6(16)9(19)12(22-3)23-10-4(2-14)21-11(20)8(18)7(10)17/h3-20H,1-2H2/t3-,4-,5+,6+,7-,8-,9-,10-,11-,12+/m1/s1 checkY
  • InChI=1/C12H22O11/c13-1-3-5(15)6(16)9(19)12(22-3)23-10-4(2-14)21-11(20)8(18)7(10)17/h3-20H,1-2H2/t3-,4-,5+,6+,7-,8-,9-,10-,11-,12+/m1/s1
  • C([C@@H]1[C@@H]([C@@H]([C@H]([C@@H](O1)O[C@@H]2[C@H](O[C@H]([C@@H]([C@H]2O)O)O)CO)O)O)O)O
Molar mass 342.297 g·mol−1
Appearance White solid
Density 1.525 g/cm3
Melting point 252 °C (anhydrous)
202 °C (monohydrate)
195 g/L
+55.4° (anhydrous)
+52.3° (monohydrate)
5652 kJ/mol, 1351 kcal/mol, 16.5 kJ/g, 3.94 kcal/g
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g. sodium chlorideFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
Flash point 357.8 °C (676.0 °F; 631.0 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
« Back to Glossary Index