Porosity of microcapsules with wall systems consisting of whey proteins and lactose measured by gas displacement pycnometry

Porosity characteristics of anhydrous milkfat-containing, spray-dried microcapsules with wall systems consisting of mixtures of whey proteins and lactose were investigated by gas displacement technique, using helium and nitrogen as displacing gases. Microcapsules exhibited molecular-sieve type porosity. Results indicated that 8-12% of microcapsule volume was inaccessible to helium. Permeation of nitrogen to wall matrices was inversely proportional to lactose content. Pore volume that was inaccessible to nitrogen penetration ranged from 0.128 to 0.263 cm(3)/g for core-free and from 0.121 to 0.214 cm(3)/g for core-containing capsules. It was affected by wall composition and core load. Results suggested that adjusting microcapsule composition could modulate gas penetration into microcapsules.