Spray- or freeze-drying of casein micelles loaded with Vitamin D2: Studies on storage stability and in vitro digestibility

Casein micelles (CM) loaded with Vitamin D2 (Vit. D2) were spray- and freeze-dried at pilot scale. The powders showed constant Vit. D2 contents over four months of storage. The CM structure was retained after processing and drying. Low fat yoghurt was enriched with the spray-dried powder or with free Vit. D2. An in vitro proteolysis showed that 90% of the Vit. D2 added as an encapsulated product, e.g. dried CM, remained active compared to only 67% when Vit. D2 was supplemented as a free substance. Since all proteins were hydrolysed after in vitro proteolysis, it can be assumed that the Vit. D2 contents determined would be ultimately available in the lumen.