Jan 24, 2008

frothing milk

yesterday, i watched closely as a colleague who used to be a professional snooty coffee maker steamed up some milk for a latte. he manages to produce, each time, steamed milk with froth of a mousse-like consistency, full of microscopic bubbles and dense, yet light, like well-whipped cream (which it is, sort of). i took copious notes, experimented throughout the day, and was able to abstract the following principles:

  • non-fat milk produces lame results -- don't use it. 2% is fine, full-fat produces no difference that i can detect once diluted with a shot of espresso.
  • good milk tastes so much better than bad milk that it is a crime to drink anything else. we get quite good milk from clover stornetta in the north bay. they have a sweet mascot and some appealingly dorky billboards.
  • the milk must be cold in order to absorb enough steam and heat to froth well without cooking. some people put the milk and steaming container in the freezer while pulling the espresso shot, but that seems excessive.
  • use a thin-walled metal container to steam the milk so that you can feel the temperature changes with minimal delay.
  • regardless of the container you use, have 3-4 inches of milk in it.
  • before activating the steam, place the tip of the steamer about a half-inch under the surface of the milk, off-center. cup the container in your hand instead of using the handle.
  • steam on, and immediately bring the tip of the steamer just under the surface of the milk, still off-center. you should see a controlled roil, not a furious bubbling. it should look a little like this picture of the churning of the sea of milk.
  • the surface of the milk will begin to look thick and glossy after 5-10 seconds and the milk should be warmish but not hot. at this point, push the tip of the steamer to the bottom of the container, as far off to the side as possible to encourage a swirly, vortex-esque movement of the milk. the vortex ensures that the heating is uniform.
  • your hand should still be cupping the container; shut off the steam before the container becomes too hot to hold comfortably.
once done steaming, tap the container against a hard surface to pop the big, vulgar bubbles and leave only the smallest, finest-textured ones behind.

max the steaming fiend points out that my instructions can be modified with similarly good results and that there is a distinction between foam and the frothy mousse that the latte fan seeks. he's right, of course. so this is max:
using my office steamer i've found that i can use the side of the container to produce a vortex and moderate the steam jet. if you steam a lot of milk (several inches deep) slowly without disrupting the surface at all, you build up volume and glossy microbubbles. then at the very end when its warm i move up to about a third to a half an inch beneath the surface and fill the container.
this glossy thick mousse is different than foam - for foam (and so, i think for cappuccinos) the skim is best.
if you add honey you get something which can sometimes be burnt but if you get the temp right is almost like meringue.

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