PARTICLE STRUCTURES OF ENCAPSULATED MILKFAT POWDERS

Emulsions of milkfat (cream or anhydrous butteroil), carbohydrate (suc rose, 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 scan ning electron microscopy. Powder particles were generally spherical in shape, with particle size distributions ranging from 20 to 120 mu m; surface morphology of the particles could be related to the encapsulan t used. Butteroil was more readily encapsulated than cream in all case s; butteroil-containing powders contained less extractable fat than di d 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 detrim ental to long-term storage. Powders with all-purpose flour as the enca psulant showed loose matrices enclosing large fat droplets, demonstrat ing structural weakness. Fat droplets were enclosed without central vo ids within the capsules when sucrose was the encapsulant; with less th an 6 g/100g extractable fat, sucrose encapsulated milkfat powders were structurally stable, suggesting good resistance to air/oxygen diffusi on during storage.