**3.3 Reaction pathways**

Lactitol is the main product formed during the hydrogenation of lactose, followed by a considerable formation of lactulose, lactulitol, lactobionic acid, sorbitol, and galactitol [23]. All these compounds are formed through a combination of hydrogenation, isomerization, hydrolysis, and oxidation. **Figure 3** illustrates the reaction pathways occurring during the hydrogenation of lactose. A number of factors influence the occurrence and extent of a given reaction. Temperature, pressure, pH, agitation, type of catalysts, concentration, and catalyst load are examples of such factors [2].
