Supercritical technology as an alternative to fractionate prebiotic galactooligosaccharides

In the present work, supercritical technology based on carbon dioxide has been used as an alternative to fractionate galactooligosaccharides (GOS) in a dairy-based prebiotic ingredient. The main challenge of the fractionation of the commercial mixture is the combination of GOS with monosaccharides and disaccharides. Considering that the beneficial health effects of the commercial mixture, such as the improvement of the immune system, have been associated to its GOS content, therefore, a purification and/or removal of other sugars can be of great importance.The goal of this study was focused in the fractionation of the complex carbohydrate mixture according to the degree of polymerization of the different carbohydrates. Supercritical carbon dioxide (SC-CO2) with different ethanol/water mixtures as co-solvents has been tested for the selective recovery of the prebiotic carbohydrates. The appropriate selection of the co-solvent employed, together with the most suitable extraction conditions (including temperature, pressure and co-solvent flow rate) allowed the almost complete removal of monosaccharides and disaccharides from the mixture and lead to a residue in the extraction cell where mainly tri- and tetra-saccharides were present with ca. 75 wt% of purity and 94% recovery.