In milk for latte and cappuccino, fat content is not important, but the protein content - consistency of foam depends on its: (a high) protein content, the foam is viscous and oily; (a small) dry and coarse-grained. Experienced barista prefers a percentage of protein from 2.8 to 3.8%. While boiling, proteins’ structure collapses and loses their properties. Therefore, tasty and thick foam is obtained only from raw (pasteurized) milk, of course, not powdered.