WHEY PROTEINS AS MICROENCAPSULATING AGENTS - MICROENCAPSULATION OF ANHYDROUS MILKFAT - STRUCTURE EVALUATION

Microencapsulation of milkfat may open new fields of application for t his milk constituent by transforming it into dry and stable powder. Re search 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 w ere evaluated as microencapsulating agents (wall materials). The effec ts of wall composition, fat load, and drying conditions on the capsule 's structure were studied by scanning electron microscopy (SEM). Spher ical capsules with smooth, wrinkle-free surfaces were observed in all cases. Whey protein isolate-based microcapsules dried at a temperature higher than 105-degrees-C were free of surface indentation and only a limited extent of indentation was observed when whey protein concentr ate served as the wall material. Microcapsules prepared from emulsions containing more than 10% wall solids and dried at 160-degrees-C exhib ited no cracks or holes. Comparing the microstructure of spray-dried m icrocapsules with and without milkfat (prepared under the same conditi ons) suggested that high milkfat load limits the extent of surface ind entation. The milkfat was encapsulated as 50-600 nm particles that wer e uniformly distributed throughout the interior of the wall matrices. No visible pores or cracks exposing the core material to the environme nt were detected. The results suggest that whey proteins can be consid ered as microencapsulating agents for anhydrous milkfat.