Using the principle of lowest solubility at the isoelectric point, when the pH of milk is adjusted to 4.7, casein will sink to the bottom and fat will be at the top

You can use the salting out method. Weighted metal ions, organic acids, organic solvents, etc. can all precipitate proteins. After protein precipitation, centrifuge for 10 minutes (3000r/min). Wash twice with water and centrifuge for 10 minutes (3000r/min).

Add ethanol, stir, and transfer the suspension to a Buchner funnel for suction filtration. Wash the precipitate twice with ethanol-ether mixture. Finally, wash the precipitate twice with diethyl ether and drain it. The precipitation is air-dried to obtain pure casein protein. Organic solvents are added to remove lipid impurities.