found this...
http://www.bodybuilding.com/store/mic.html
line from article:
Micellar casein is the natural, undenatured form of casein found in milk. It is separated from milk by means of ultrafiltration, without the use of chemicals, which increases the amount of bioactive milk peptides that support immune function as well as enhance muscle growth. A property of micellar casein is that it may have the ability to form a "gel" in the gut. This provides a steady release of amino acids into the blood stream, which makes it an excellent choice for a long lasting anti-catabolic protein