Chromatographic purification and characterization of whey protein-dextran glycation products

A process for the food-grade preparative-scale production and chromatographic purification of whey protein isolate (WPI)-dextran glycates was developed in this work. The Maillard reaction was used to produce the glycates in aqueous solution. A 5 mL cation exchange column and salt step gradients were utilized to elute the glycated protein at low salt and unreacted protein at high salt. The process was scaled-up 160-fold to an 800 mL column. Glycated products were analyzed by SDS-PAGE, BCA protein assay and glycoprotein carbohydrate estimation kit, MALDI-TOF and static and dynamic light scattering. Glycated protein was relatively pure, containing only traces of beta-lactoglobulin, and it was heterogeneous due to oligo-glycation. It had a molecular mass of 26-35 kDa by static light scattering, and 22-67 kDa by MALDI-TOF. Mono-glycated protein would have been 23.8 kDa from beta-lactoglobulin (18.6 kDa) and dextran (5.2 kDa). This work demonstrated the utility of cation exchange chromatography for the large-scale purification of glycated proteins using food-grade chemicals and procedures.