Why do egg custard have smell of boiled milk?

Egg custard has a smell reminiscent of boiled milk due to the proteins in the eggs denaturing and interacting with the lactose in the milk during cooking. When heated, the proteins undergo changes that can release compounds contributing to that distinct aroma. Additionally, the Maillard reaction, which occurs during cooking, can enhance these smells and flavors. This combination of factors creates the characteristic scent associated with egg custard.