Any one or more of the following mistakes can scorch milk and cause it to stick: heating milk too high a temperature; heating for too long; infrequent and incomplete stirring; heating in a thin-bottomed pan. And the staler the milk, the more likely it will scorch. Scorched milk gives preparations a burnt off-flavor and human dishwashers a time-consuming chore. What burns and tenaciously sticks are the milk's protein and lactose (milk sugar). When lactose caramelizes, it imparts an unwanted flavor and color to your heated milk.