Galactooligosaccharides (GOS) are prebiotic carbohydrates that have been shown to have bifidogenic properties and are often added to infant formula as a supplement to match the composition of human milk. As such, they garner a 10-fold cost in the marketplace and so offer an attractive value addition for the dairy industry. These compounds are usually synthesized via trans-galactosylation of lactose. GOS are typically simple structures and comprise mainly tri- and tetra-saccharides made up of glucose and galactose residues. Typically the trans-galactosylation reaction is incomplete, and so glucose, galactose, and lactose remain at the end . Trans-galactosylation is catalyzed by P-galactosidases as these enzymes possess simultaneous hydrolytic and transgalactolytic activities, and so yield a heterogeneous mixture of carbohydrates having different chain lengths . Cho et al.  compared the GOS formation in both pure lactose solution and whey permeate. GOS concentrations of 41% and 34% of total carbohydrates from lactose and whey permeate were achieved, respectively. Hereby, the degree of polymerization (DP) in cheese whey permeate was primarily three, with some tetrasaccharides and pentasaccharides as well. The results indicate that whey permeate is a suitable inexpensive raw material for the production of simple GOS.
Other Lactose Derivatives
In addition to the aforementioned lactose derivatives, there are several minimally- investigated compounds worth mentioning. These include lactosucrose, lactobionic acid, and lactitol. Current research has focused on the production of those derivatives with pure lactose feedstock with practically no research utilizing whey permeate as feedstock. It is necessary to optimize both upstream and downstream processes if processes are to be adapted for whey permeate as an inexpensive raw material for the production of these derivatives.