Analysis of the Maillard reaction products of beta-lactoglobulin and lactose in skimmed milk powder by capillary electrophoresis and electrospray mass spectrometry.

When analysed by capillary electrophoresis, certain skimmed milk powders are seen to exhibit additional peaks migrating after the whey protein beta-lactoglobulin. Using a model reaction between beta-lactoglobulin and lactose, and studying the reaction products using electrospray mass spectrometry, it is demonstrated that these protein peaks are almost certainly due to a Maillard reaction between lactose and the epsilon-amino group of lysine. This results in the formation of a series of lactulose-protein conjugates exhibiting throughout molecular mass increments of 324, which is sufficient to allow their separation by capillary electrophoresis.