oligosacharides are formed when 3 to 10 monosaccharide units combine with each other by the loss of water molecules, resulting in the formation of a glycosidic linkage. conversely hydrolysis of an oligosaccharide in water in the presence of an acid or enzyme yields 3 to 10 monosaccharide units. oligosaccharides which consist of two monosaccharides units are called as disaccharide. oligosaccharides containing 3 monosaccharides are called trisaccharides.