Monitoring In Vitro Enzymatic Digestion of Lactose in Milk Using Microdialysis with Pulsed Amperometric Detection

Abstract

In vitro microdialysis is used for monitoring the hydrolysis of lactose toglucose and galactose in milk. The reaction is catalyzed by Lactaid®drops, which contain β-galactosidase. A microdialysis cell designed forin vitro use is described. Use of a low molecular weight cut-off membraneas well as high perfusion rates permits direct injection and analysis of thedialysate without additional sample clean-up or dilution. Separation anddetection of lactose is accomplished by high performance anion exchangechromatography (HPAEC) followed by pulsed amperometric detection(PAD). Observed rate constants for this reaction at 5º C are determinedin skim (fat free) as well as whole milk. This technique is generallyapplicable to the study of exo- and endoglycosidases and other enzymereactions with carbohydrate-based substrates.