Characterization of glycated lysozyme with galactose, galactooligosaccharides and galactan: Effect of glycation on structural and functional properties of conjugates

Glycated lysozyme (LZM) with galactose, galactooligosaccharides (GOSs) and galactan, through the Maillard reaction, were produced and characterized structurally and functionally. The extent of glycation of LZM was evaluated by the measurement of the blocked lysine and the formed furosine. The results indicated a high initial reactivity of galactose as compared to GOSs and galactan. In the presence of GOSs, the oxidative and cross-linking side reactions competed with the initial formation of Amadori product. The longer chain carbohydrate galactan exhibited the lowest initial rate of glycation with no significant cross-linking side reaction. Electrospray ionization mass spectrometry revealed the formation of glycated LZM containing up to eight galactose moieties; while only mono- to tetra-glycated LZM with GOSs were detected. 2-3 mol of galactan were conjugated to 1 mol of LZM. Galactan:LZM conjugates exhibited higher solubility, thermal stability and emulsion stability as compared to the unmodified LZM and LZM:galactose conjugates. LZM:GOS conjugates demonstrated the most improvement in the emulsion stability than the other conjugates. Furthermore, the glycation of LZM with galactose/GOSs/galactan decreased its immunoreactivity. (C) 2013 Elsevier Ltd. All rights reserved.