Galacto-oligosaccharides(GOS) occur naturally in human milk. GOS are soluble non-digestible carbohydrates,structured as chains of galactose with a glucose end-piece. GOS are produced through the enzymatic conversion of lactose. During an enzymatic process, lactose is first cut in glucose and galactose. After cutting, the enzyme builds sugar strings of different lengths from galactose with one glucose unit. Comprised of di-, tri-, tetra-, penta-, and hexasaccharides, mainly consisting of galactose units.