Summary To apply native casein micelles (CM) as nanocarriers for lipophilic substances in non‐ or low‐fat food products, they have to be conditioned before loading. In this study, an experimental set‐up for the production and loading of CM was developed. Microfiltration was used to separate CM from skimmed milk. To identify optimal loading conditions temperatures (2, 20, 40 °C), pH values (6.8 and 5.5) and holding times (5, 15, 30, 60 min) were varied. The release of calcium, phosphate and protein from the micellar phase as well as static light scattering and transmission electron microscopy showed that CM were optimally primed at 2 °C and a pH of 5.5 for 5 min. Therefore, loading with β‐carotene was performed under those conditions. After the back‐extraction of β‐carotene, the photometrical analyses revealed total recovery rates of >79% whereby 94% of it was associated with the native CM.

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Application of casein micelles (CM) as nanocarriers for lipophilic substances was studied. Casein micelles were separated from skimmed milk by microfiltration. Casein micelles were partly dissociated at 2°C, pH 5.5, and loaded with b-carotene, vitamin D2 or docosahexaenoic acid (DHA). Loading concentrations and times were varied. Loading efficiency was in the order: bcarotene > vitamin D2 > DHA. Optimal loading times were 60 min for b-carotene and 15 min for vitamin D2 and DHA. Adding whey protein to loaded CM led to lower vitamin D2 content in the micellar phase. Heat treatment (85°C/2 min) led to stable loading concentrations over 4 days of storage.

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