 The degree of polymerization of GOS can vary quite markedly, ranging from 2 to 8 monomeric units, depending mainly on the type of the enzyme used and the conversion degree of lactose.Because of the configuration of their glycosidic bonds, galacto-oligosaccharides (GOS) largely resist hydrolysis by salivary and intestinal digestive enzymes.Galacto-oligosaccharides are classified as prebiotics, defined as non-digestible food ingredients that beneficially affect the host by stimulating the growth and/or activity of beneficial bacteria in the colon.