Partakalvo

Partakalvo refers to the visible film that forms on the surface of liquids, particularly milk and dairy products, when they are heated. This phenomenon is primarily due to the denaturation and coagulation of proteins, especially whey proteins like lactalbumin and lactoglobulin, along with some milk fat.

When milk is heated, the liquid phase shrinks slightly as water evaporates. Simultaneously, the proteins, which are suspended in the milk, begin to change their structure. These denatured proteins then aggregate and form a mesh-like structure that traps fat globules and other components. This structure solidifies as it cools or continues to be heated, creating the distinct skin or film. The thickness and texture of the partakalvo can vary depending on the temperature, duration of heating, and the composition of the milk.

The formation of partakalvo is a common observation in cooking and food preparation. While some may find it undesirable and remove it, others incorporate it into dishes. For instance, it is a key component in the preparation of certain traditional dishes in various cultures. The chemical and physical changes that lead to its formation are well-understood in food science, relating to protein behavior under thermal stress.