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Food Structure

Abstract

Microencapsulation of milkfat may open new fields of application for this milk constituent by transforming it into dry and stable powder. Research has been undertaken to study the microstructure of whey protein based, anhydrous milkfat-containing, spray-dried microcapsules. Whey protein concentrates of 50% and 75% protein and whey protein isolate were evaluated as microencapsulating agents (wall materials). The effects of wall composition, fat load , and drying conditions on the capsule's structure were studied by scanning electron microscopy (SEM). Spherical capsules with smooth , wrinkle-free surfaces were observed in all cases. Whey protein isolate-based microcapsules dried at a temperature higher than 105 °C were free of surface indentation and only a limited extent of indentation was observed when whey protein concentrate served as the wall material. Microcapsules prepared from emulsions containing more than 10% wall solids and dried at I6o•c exhibited no cracks or holes. Comparing the microstructure of spray-dried microcapsules with and without milkfat (prepared under the same conditions) suggested that high milkfat load limits the extent of surface indentation. The milkfat was encapsulated as 50-600 nm particles that were uniformly distributed throughout the interior of the wall matrices . No visible pores or cracks exposing the core material to the environment were detected. Theresults suggest that whey proteins can be considered as microencapsulating agents for anhydrous milkfat.

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