Core-shell particles formed by β-lactoglobulin microgel coated with xyloglucan.

Core-shell particles were formed by mixing in aqueous solution the neutral polysaccharide xyloglucan (XG) with microgels. The last one was obtained by heating the whey protein β-lactoglobulin (β-LG) in the presence of CaCl2. XG adsorbed spontaneously unto the microgels at pH<5.6. The amount of bound XG per protein was determined using a combination of centrifugation and size exclusion chromatography. It increased linearly with increasing XG concentration. The fraction of XG that adsorbed increased with decreasing pH. The formation of the XG shell inhibited large scale flocculation of the particles, that causes precipitation for naked microgels, close to their isoionic point. The thickness of the XG shell was estimated by measurement of the hydrodynamic radius using dynamic light scattering. The extent of binding depended on the pH history during mixing showing that the protein/XG complex was not in thermodynamic equilibrium.