Casein is the major component of protein found in bovine milk accounting for nearly 70-80% of its total protein and is responsible for the white color of milk. It is the most commonly used milk protein in the industry today. Milk proteins are of significant physiological importance to the body for functions relating to the uptake of nutrients and vitamins and they are a source of biologically active.
The nutritional protein quality of lactose-hydrolysed milk after some industrial processes was studied with N balance experiments on growing rats. Ultra-high-temperature sterilization and evaporation at 25 °C did not influence the nutritional value significantly, whereas spray-drying under conditions usually used for ordinary milk gave a considerable reduction in protein quality