The question of whether milk should be heated and boiled troubles many people. Experts say that boiling milk will result in some loss of nutrients, and the longer it is boiled, the greater the loss. If you want to drink warm milk, it is best to warm it properly in one of three ways.
First, simmer it over low heat, stirring constantly to prevent the milk at the bottom and sides of the pot from scorching due to excessive heat. You can turn off the heat when steam begins to rise from the surface. Second, use a microwave. When heating fresh carton milk in a microwave, you must first open the carton. For bottled milk, remove the aluminum cap first. Heat for several tens of seconds. However, this method is not suitable for ambient temperature milk because its composite packaging material contains an aluminum foil layer. Third, heat it by soaking in hot water. Place the milk in warm water at about 50°C (122°F) and soak for 5-10 minutes.
As the milk is heated, surface water evaporates, causing the protein to concentrate and coagulate. The surrounding fat and lactose then envelop the protein, forming a layer, which some people call "milk skin." This milk skin thickens as the heating time increases and the temperature rises. Experts remind us that the milk skin contains nutrients such as protein, fat, and lactose, so it should not be discarded. If you want to prevent the formation of a milk skin, you need to stir the milk continuously after heating it.