Glycoprofiling of Oligosaccharides of Regular and Lactose-Free Milk by Mass Spectrometry

Abstract

Oligosaccharides from regular milk and lactose-free milk were analyzed by Electrospray Ionization interface coupled with Ion Trap Mass Spectrometry (IT-MS). The negative mode mass spectrometry of sugar compositions was obtained either by direct infusion and mass spectrometry with Liquid Chromatography (LC). Hexose (Hex) and the other oligomeric sugar components were observed in both regular and lactose-free milk. While lactose derivatives (deprotonated lactose dimer, chloride adducts, chloride dimer) in regular milk have seen to be dominated, monosaccharide derivatives (Hex-H2O, Hex, Hex-Cl) in the lactose-free milk were observed as abundant which was lytic product of lactose. Phosphate/sulfate ester substitution on lactose and sialyllactose in both regular and lactose-free milk samples were observed with similar intensity thus it has been understood that these important milk components are not digested during lactose removing process.