Particle structures of encapsulated milkfat powders

Abstract

Emulsions of milkfat (cream or anhydrous butteroil), carbohydrate (sucrose, modified starch or all-purpose flour), nonfat dry milk and mono-and diglycerides as emulsifying agents were prepared and spray-dried, yielding free-flowing powders containing 400, 500 or 600 g/kg milkfat. Structural features of the powders were evaluated by optical and scanning electron microscopy. Powder particles were generally spherical in shape, with particle size distributions ranging from 20 to 120 μm; surface morphology of the particles could be related to the encapsulant used. Butteroil was more readily encapsulated than cream in all cases; butteroil-containing powders contained less extractable fat than did those made with heavy cream. Milkfat was distributed in the walls of the powder particles when modified starch was the encapsulant; these particles contained occluded air in their cores, which could be detrimental to long-term storage. Powders with all-purpose flour as the encapsulant showed loose matrices enclosing large fat droplets, demonstrating structural weakness. Fat droplets were enclosed without central voids within the capsules when sucrose was the encapsulant; with less than 6 g/100g extractable fat, sucrose encapsulated milkfat powders were structurally stable, suggesting good resistance to air/oxygen diffusion during storage. ©1996 Academic Press Limited.