MICROSTRUCTURE AND FAT EXTRACTABILITY IN MICROCAPSULES BASED ON WHEY PROTEINS OR MIXTURES OF WHEY PROTEINS AND LACTOSE

Research was undertaken to determine the microstructure of whey protei n/lactose-based, anhydrous milkfat-containing, spray-dried microcapsul es and to study the relationship between core extractability and the s tate of lactose in these microcapsules. Spherical microcapsules nearly free of surface dents were obtained in all cases. The milkfat was fou nd to be organized in the form of small droplets (0.2-0.8 mum) embedde d in the capsule wall. The surface topography of the capsules exhibite d features that may be linked to removal of milkfat droplets from the outer surfaces at early stages of the drying. Lactose crystallization was observed after incubation at water activity of 0.53 and progressed at higher relative humidity which also resulted in significant change s in the original capsule's structure. Lactose crystallization was evi dent on both the outer surfaces of the capsules and on the surface of inner voids. Larger proportions of encapsulated milkfat could be extra cted by petroleum ether from whey protein-based capsules than from whe y protein/lactose-based ones. Lactose crystallization led to an increa se in the amount of milkfat that could be extracted from the capsules from 19 mg/g solids before incubation up to 260 mg/g solids after incu bation at water activity of 0.9. The results indicated that lactose in its amorphous state limits the extractability of milkfat from the cap sules.