The word “micelle” is a chemical term. It is used to describe the structure that certain very large molecules will form when dispersed in a solvent. Believe it or not, water is considered to be a solvent (chemicals are made soluble in water). Very large molecules are considered to be too large to be truly soluble in water. Instead, these large molecules will form structures that allow them to remain suspended in water as if they are soluble. The dispersion of these large structures in water is known as a colloidal suspension. The structures that allow large molecules to remain colloidally suspended in water are termed micelles. Under an electron microscope, micelles often look like little spheres. In the case of casein, the parts of the casein molecules that have an affinity for water form the outside of the casein micelle. Conversely, the parts of the casein molecule that are repelled by water form the inner core of the micelle spheres.
When casein molecules are manufactured by a mammal, they are manufactured in water (cow’s milk is 88% water). As the casein molecules are formed, they begin folding up into a spherical micelle structure so that the casein proteins can remain suspended indefinitely in the milk water. Along with the casein proteins in the micelle, important milk minerals, such as calcium and phosphorous also become bound inside the micelle. The micelle structure of casein is its natural structure. The micelle structure can be easily disrupted or changed – by addition of acid or alkali to milk – or by extreme heat exposure. Products such as acid casein, rennet casein and any and all caseinates no longer contain casein in its micelle form. These products are all manufactured in such a way that the micelle colloidal suspension in milk has been destroyed. Once a casein micelle is destroyed, it will not re-form. Over the years many attempts have been made to rebuild casein micelles after they have been destroyed. To date, nobody has been successful.