Question

I am currently studying about the biochemistry of yoghurt and when reading about the effect of heat in milk proteins specifically whey, my book says that heat can denature whey proteins. So after the denaturation will the whey proteins coagulate and then peripitate? If that is the case why in yoghurt that hasn't been homogenized, a layer of whey protein and fat forms on top. For example traditional greek yoghurts all form this top layer because they are left to cool down without any homogenization. Does the denatured whey proteins go up or down?

Answer 1

Upon heat denaturation, whey proteins in milk can coagulate, forming a network that contributes to yogurt's texture. In non-homogenized yogurt, such as traditional Greek yogurt, the denatured whey proteins may rise with the fat, forming a distinct top layer.

Step-by-step explanation:

When proteins are exposed to heat, their structure can change in a process known as denaturation. Commonly seen when frying an egg, the clear liquid turns opaque as the albumin protein coagulates. While this denaturation can render proteins incapable of their original function, not all proteins denature in the same conditions and some may be adapted to function at higher temperatures.

In the context of yogurt production, heat denaturation of whey proteins in milk results in their coagulation and formation of a network that traps fat and water, contributing to the yogurt's texture. However, not all whey proteins will visibly coagulate and precipitate, and some may interact differently depending on the specific conditions and treatment of the milk, like homogenization. When yogurt is not homogenized, a separation occurs where fat rises to the top, carrying with it some denatured whey proteins, leading to the formation of a layer on traditional Greek yogurts.