Why does milk steamed to 165 degrees feel cooler than apple cider steamed to the same temperature?
I’ll lay odds that it is due to the foam, the bubbles entrained in the milk in the steaming process. As a composite of air and milk, foam will have a lower specific heat than liquid milk itself at the same temperature. When you touch the foam, it must transfer heat to your skin for you to feel the perception of heat. Lower specific heat means that less heat will be transferred. A second related factor is heat conduction/convection. When you touch some foamy milk, the heat must transfer to your skin. This causes your skin to warm up, but at the same time the foam right near your skin in a boundary layer cools down. Heat will flow into that boundary layer cooling down the entire volume of foam. However, bubbles are a good insulator, even a great one. So the heat flows in slowly. You don’t burn your tongue. What happens with a non-bubbly liquid? Conduction is much faster. As well, convection will now be a significant factor, whereas it will not be as important in a foam. So the hot liquid
