Porosity of whey protein-based microcapsules containing anhydrous milkfat measured by gas displacement pycnometry

Porosity characteristics of spray-dried microcapsules consisting of whey proteins and anhydrous milkfat were investigated by gas displacement technique, using helium and nitrogen as displacing gases. Microcapsules exhibited molecular-sieve type porosity. True and apparent densities as well as porosity characteristics were affected by wall solids concentration and by core load. Results indicated that about 10% of capsule volume was not accessible to helium. Pore volume inaccessible to nitrogen penetration was affected by cove load and solid concentration. Results suggested that porosity, and hence gas-permeation into microcapsules, could be tailored by adjusting microcapsules composition.