Why does heating milk cause it to stick to the bottom of the pot

Heating milk to make the bottom of a pot is mainly the result of the combined action of protein denaturation precipitation and lactose caramelization reaction. Milk contains a large amount of protein and lactose. Under high temperature, the protein structure is disrupted to form a precipitate, while lactose is thermally decomposed to produce caramel substances. The two adhere to the bottom of the pot to form a paste.

The protein in milk begins to gradually denature at above 60 ℃. When the temperature exceeds 80 ℃, the main proteins such as casein will change from dissolved state to gel like precipitation. These sediments have a high density and are prone to settling at the bottom of the heating container. At the same time, lactose in milk undergoes Maillard reaction during continuous heating, producing brown caramel like substances with strong viscosity. When heated directly with an open flame, the local temperature at the bottom of the pot may exceed 100 degrees Celsius, far exceeding the tolerance limit of the ingredients in milk. The thermal conductivity of stainless steel or aluminum cookware accelerates the formation of a high-temperature zone at the bottom, while the high viscosity of milk leads to uneven heat distribution. If not stirred in time, the sediment at the bottom will carbonize when in contact with the pot body for a long time, and eventually black burnt matter will adhere to the bottom of the pot and be difficult to remove.

To avoid milk from heating up and sticking to the pot, it is recommended to use a water-resistant heating method to control the temperature below 70 degrees Celsius, and maintain gentle stirring throughout the process to evenly distribute the heat. Choose a thick bottomed stainless steel pot or a specialized milk pot, and wet the bottom of the pot with water before heating to form a protective layer. Immediately turn off the heat when there is a slight burnt pot, soak it in warm water, and gently brush it to avoid scratching the surface of the pot with a steel wire ball. When drinking milk in daily life, refrigerated milk does not need to be boiled, and warming it to the appropriate drinking temperature can retain more nutrients.