Sub-structure of synthetic casein micelles

Area of Science:

• Dairy science
• Biochemistry
• Materials science

Background:

• Casein micelles are complex colloidal particles essential for milk's structure and nutritional properties.
• Previous research using freeze-fracturing showed no substructural differences between natural and artificial micelles (Ca and casein only).

Purpose of the Study:

• To investigate the sub-structure of synthesized casein micelles.
• To determine the necessary ionic components for creating artificial micelles that replicate natural micelle substructure.

Main Methods:

• Synthesis of casein micelles with varying compositions.
• Investigation of micelle sub-structure using electron microscopy of thin sections.

Main Results:

• Contrary to prior findings, artificial micelles require calcium, phosphate, and citrate ions to match natural micelle sub-structure.
• Citrate ions are vital for forming the dark framework observed in electron micrographs of unstained thin sections.

Conclusions:

• The presence of phosphate and citrate ions, in addition to calcium, is essential for the formation of natural-like casein micelle sub-structure.
• Findings support the hypothesis that casein micelles contain citrate apatite, with citrate playing a key role in their structural integrity.