Food Structure

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Research was undertaken to determine the microstructure of whey protein/lactose-based , anhydrous milk fat- containing , spray -dried microcapsules and to study the relationship between core extractability and the state of lactose in these microcapsules. Spherical microcapsules nearly free of surface dents were obtained in a ll cases The milkfat was found to be organized in the form of small droplets (0.2-0.8 um) embedded in the capsule wall. The surface topography of the capsul es ex hibited features that may be li nked to removal of mil kfat drop lets from th e outer surfaces at early stages of the dryin g. Lactose crystallization was observed after incubation at water activity of 0.53 and progressed at higher relative humidity which also resulted in significant changes in the original capsule's structure. Lactose crystallization was evident on both the outer surfaces of the capsules and on the surface of inner voids. Larger proportions of encapsulated milkfat could be extracted by petroleum ether from whey protein-based capsules than from whey protein/lactose-based ones. Lactose crystallization led to an increase 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 incubation at water activity of 0 .9. The results indicated that lactose in its amorphous state limits the extractability of milkfat from the capsules.

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