1. Overview & Physics
Protein Emulsion Dynamics
Milk microfoam is a transient gas-liquid emulsion. Steaming injects air, while whey proteins denature to form a protective layer around the air bubbles. However, if milk temperature exceeds 70째C, the proteins collapse. The microfoam decays rapidly, separating into water and dry foam, losing the glossy 'wet paint' texture required for pouring latte art.
Microfoam Maintenance
Stop steaming immediately when the pitcher bottom is hot to the touch. Tap and swirl the pitcher to maintain emulsion integration before pouring.
2. Practical Calibrations
Managing this requires measuring indicators in real time. Adjust grind size, water dynamics, and flow parameters incrementally. Change only one variable at a time to ensure clean results and isolate target parameters.
Barista Action Checklist
- Weigh dry grounds dry dose exactly to 0.1g.
- Calibrate water temperature using PID sensors.
- Target correct brew ratios (e.g. 1:15 for filter, 1:2 for espresso).
- Swirl or stir to ensure even saturation during extraction.
- Record extraction time and evaluate flavor notes subjectively.
Frequently Asked Questions
Why does over-steamed milk separate?
Steaming past 70째C denatures whey proteins completely, causing them to lose their bubble-trapping elastic structure, separating into thin milk and dry foam.
What temperature is best for milk sweetness?
The sweet spot is 60째C to 65째C, where fats melt and lactose is perceived as sweet without burning.
