Lactose

Lactose is a disaccharide sugar derived from galactose and glucose that is found in milk. Lactose makes up around 2–8% of milk (by weight), although the amount varies among species and individuals, and milk with a reduced amount of lactose also exists. It is extracted from sweet or sour whey. The name comes from lac or lactis, the Latin word for milk, plus the -ose ending used to name sugars. It has a formula of C₁₂H₂₂O₁₁ and the hydrate formula C₁₂·11H₂O, making it an isomer of sucrose.

History

The first crude isolation of lactose by Italian physician Fabrizio Bartoletti (1576–1630) was published in 1633. In 1700, the Venetian pharmacist Lodovico Testi (1640–1707) published a booklet of testimonials to the power of milk sugar (saccharum lactis) to relieve, among other ailments, the symptoms of arthritis. In 1715, Testi's procedure for making milk sugar was published by Antonio Vallisneri. Lactose was identified as a sugar in 1780 by Carl Wilhelm Scheele.

In 1812, Heinrich Vogel (1778-1867) recognized that glucose was a product of hydrolyzing lactose. In 1856, Louis Pasteur crystallized the other component of lactose, galactose. By 1894, Emil Fischer had established the configurations of the component sugars.