HOW DUMPLINGS ARE FORMED ON THE UPPER SURFACE OF THE MILK:
Milk is a colloid and a mixture of water, fat, protein, carbohydrate and minerals. When the milk is boiled, the fat and the protein are separated from other products due to heat and are accumulated on the surface of the milk, as their density is less. At that time, they join with each other and spread as dumpling on the surface of the milk. The water substance in the milk reaches the boiling point and change into steam. The steam rises upwards. But the dumpling spread on the milk prevents from going up. However the steam which has less density, go up after pushing the dumpling and released. This is called as ‘the milk effervesces’.
At the stage of ‘effervesce’, if the heat of the stove is reduced, the speed of the water reaching the boiling point. Is reduced and the effervescing will stop. If the milk is stirred with a spoon, the dumpling spreading on the milk is broken and the steam which remains at the bottom goes out. Thus the effervescence of the milk will stop.