Milk foamability - what's to blame for a flat cappuccino or a foamy cheese vat?

摘要

Foaming of milk is highly desirable for your morning cappuccino, but when pumping milk and filling vats excess foam can cause operational problems and product losses. Too much froth can be also a problem when mixing ingredients into products or reconstituting dried mixes containing milk powder. A foam is a two-phase system consisting of a distinct gas bubble phase surrounded by a continuous liquid lamellar phase. Milk foams are stabilised by milk proteins, which accumulate at the interface between the air and the liquid. The key to a good, stable milk foam is the presence of the right proteins, and the absence of other substances that might displace the proteins from this interface. The image below shows the gas bubbles in a milk foam surrounded bythe liquid lamellar phase, as well as the dark interface line where the proteins accumulate.