What is one of the main characteristics of the milk used to create microfoam?

The characteristic that milk should be pasteurized and chilled is crucial for creating microfoam, as it ensures both safety and quality. Pasteurization is a process that eliminates harmful bacteria, making the milk safe for consumption while preserving its flavor and texture, which is essential when steaming milk. Chilled milk has a higher fat content and better stability, allowing it to create a rich, silky microfoam when steamed. When milk is cold, it can be frothed more effectively, leading to the small, uniform bubbles that characterize microfoam.

The other characteristics mentioned, such as heating milk to a boiling point, foaming with no steam, and using freshly opened milk, do not directly contribute to the creation of microfoam. Boiling milk can scorch it and lead to undesirable textures, while steaming is an essential part of foaming milk correctly. Freshness is important for flavor, but milk that is pasteurized and chilled is paramount for achieving the desired foaming result.