*3.3.2 Isomerization*

The temperature used during hydrogenation may trigger the isomerization of lactose via enolization of the glucose molecule, scheme (4). Hypothetically, galactose, and glucose may undergo isomerization to form D-Tagatose and fructose, respectively. The yield corresponding to derives from isomerization is rather low. This is because the isomeric form of a reducing carbohydrate is prone to hydrogenation. Scheme (9) and (10) illustrate the hydrogenation of glucose and galactose, respectively.
