Why does raw milk curdle when heated after standing at room temperature for considerable period of time?
Milk contains a variety of microorganisms, which are capable of converting lactose present in the milk to lactic acid, increasing the acidity. When the milk is stored at room temperature (30-37°C) for considerable period of time, it provides ideal temperature for the growth of most of the spoilage causing organisms and in turn increases the acidity. When the acidity increases beyond 0.20% lactic acid, the milk clots on boiling or heating.
