Scientifically speaking, milk foams because of the proteins in the milk. As milk is heated, these proteins denature and unwind. This causes them to bond together and create a stable network of air bubbles. This network traps air, creating a thick foam on top of the liquid milk, and a beautiful silky texture in your flat white or latte.
The protein content of different types of milks varies greatly. Whole milk has a higher protein content than non-fat or low-fat milk, with around 3.3g of protein in 8 ounces of whole milk. However, non-fat or low-fat milks can contain up to 2.5g of protein per 8 ounces, while almond, coconut and soy milks contain much lower amounts of protein.
This is why whole milk is the most popular choice for foaming, as it produces the best result in terms of flavour and texture. Happy frothing! 🙂
