Microencapsulation of theophylline in whey proteins: effects of core-to-wall ratio

Effects of core-to-wall ratio ranging from 1:1.5 to 5:1.5 on formation, properties and core release from whey protein-based microcapsules containing theophylline were investigated. Microcapsules were cross-linked by glutaraldehyde-saturated toluene (GAST) in an organic phase. Size distribution of microcapsules, core content and core retention were affected by core-to-wall ratio. Proportion of small capsules was inversely related to core-to-wall ratio. Core content in microcapsules ranged from 6.7 to 65.7% (w/w) and core retention ranged from 16.8 to 85.4%. Outer topography and inner structure of microcapsules were influenced by core-to-wall ratio. Core release into simulated intestinal- and gastric-fluids was influenced by a combined effect of type of dissolution medium and core-to-wall ratio, through its influence on size, core content and structure of microcapsules. Results indicated that in order to attain a desired core content and release profile, the ratio of core-to-wall components, in suspensions consisting of whey proteins and theophylline, has to be carefully considered and adjusted.