Studying the structure of β-casein-depleted bovine casein micelles using electron microscopy and fluorescent polyphenols

•Removal of β-casein from casein micelles does not greatly alter their structures.•Casein micelles depleted in β-casein bind curcumin (hydrophobic) more strongly.•Casein micelles depleted in β-casein bind resveratrol (hydrophilic) more strongly.•This has relevance to the use of micelles to carry bioactive compounds.

Cooling of milk causes the release of β-casein from the casein micelles. With subsequent washing steps, using milk UF permeate, it was possible to remove up to 60% of its initial concentration and study the interactions of β-casein depleted micelles with two model molecules, resveratrol and curcumin. With the release of β-casein there was an increase in the apparent diameter of the casein micelles, with no changes in the amount of colloidal calcium phosphate, or to the integrity of the protein particles when observed by Cryo-TEM. In addition, there was an increase in the affinity for both curcumin, a hydrophobic molecule and resveratrol, a hydrophilic molecule. Thus, with the removal of the β-casein, there appeared to be an overall loosening of the micellar structure, giving an increase in the accessibility to the inner hydrophobic regions.

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