what are casein curds
- Cheesemaking principles. Curds and whey. Cheesemaking involves coagulating the casein protein in milk and then separating the milk into solid curds and liquid whey. The liquid whey is drained away, and the curds are salted, shaped and left to ripen in a controlled environment.owever, for most cheeses, rennet is also added to the milk after a starter bacteria. Rennet is a mixture containing the active enzyme chymosin. Rennet speeds up the coagulation of casein and produces a stronger curd.