Whey Protein-based Microcapsules Prepared by Double Emulsification and Heat Gelation

Whey protein-based microcapsules containing a model apolar core, anhydrous milkfat, were prepared using a process consisting of double emulsification and subsequent heat gelation. Wall solids concentration and core load ranged from 15 to 30 g/100 g and from 25 to 50 g/100 g (on dry basis), respectively. In all cases, spherical microcapsules, 10-100 µ m in diameter, were obtained and their outer topography and inner structure was affected by the pH of the core-in-wall emulsion. Microcapsules prepared from pH 7.2 core-in-wall emulsions exhibited smooth, dentfree surfaces. Surface porosity of microcapsules prepared from pH 4.5, 5.5 and 5.5 core-in-wall emulsions was inversely related to pH. Core retention during microencapsulation was higher than 90% and core losses could be attributed mainly to removal of core droplets from the outer surface and to some core extraction from inner parts of microcapsules by the solvents used to wash the microcapsules. Water solubility of microcapsules prepared from pH 4.5 or pH 7.2 corein-wall emulsions was very limited and ranged from 0.2 to 6.3%, was inversely related to the pH of core-in-wall emulsion and was affected by incubation conditions. Results suggested that the microencapsulation process might be used to prepare whey protein-based microcapsules for controlled core-release applications in food systems.