Frothing Extra-Foamy Milk
When it comes to frothing milk, temperature makes all the difference.
In our May/June 2011 issue, we described a way to froth milk by microwaving it in the glass beaker of a French press and then pumping the hot milk into a thick foam with the press’s plunger. Since then, we’ve found that reversing the process and frothing while the milk is still cold produces a creamier, longer-lasting, and more billowy foam.
Here’s why: Agitating milk when it’s cold lets you pump more air bubbles into it. As you pack in more air, the bubbles become smaller and the foam becomes denser. Frothing hot milk produces bigger, weaker bubbles because the proteins have already bound to one another and are less able to coat and stabilize the air bubbles. When milk is heated after frothing, however, the proteins coat the air bubbles before cross-linking and are able to reinforce the structure of the foam that’s already been created.
Here’s the updated technique:
1. Fill a French press’s glass beaker no more than one-third full with cold milk. Froth vigorously with the plunger until the milk doubles in volume (about 20 seconds).
2. Remove the plunger and microwave the beaker on full power for 30 to 45 seconds or until the foam rises nearly to the top. You can also use a sealable glass jar: Shake cold milk forcefully in the tightly sealed jar for about 20 seconds, remove the lid, and microwave the jar. (This method produces a slightly coarser foam.)
For a creamier, longer-lasting foam for your espresso, froth milk before you heat it.