How to Steam Milk for a Latte or Cappuccino at Home
Great steamed milk is the key to truly having café quality drinks at home, especially if you’d like to pour artistic designs on top. It takes a lot of practice and terrific technique to get to repeatable results every time. But we’ve found, with the right training, you can get very good within a couple weeks.
How milk steaming works
When you steam milk for a latte or cappuccino, you’re doing two things at once: making foam by introducing air and heating the milk. Here’s how and why that technique works. When you turn on your steam wand, jets of steam shoot out through the holes on the steam tip. When the steam tip is at the surface, the jets of steam act like tiny whisks—they rapidly inject air by breaking the milk’s surface and folding air into the milk. If you expose the steam tip or raise it above the surface, you’ll force large bursts of air into the milk and create big, unwieldy bubbles. But if you don’t expose the steam tip at all, the surface won’t break; the milk will still warm up from the hot steam but you won’t introduce any air, meaning no foam.
While you’re introducing air, the steam is also heating the milk and unwinding its proteins, so they can wrap around the air bubbles and form a protective jacket. This wrapping occurs because one side of the protein repels water and the other side is attracted to water. The first side clings to the air bubbles; the other side holds close the water in the milk. This action captures air in the liquid and gives milk its unique foaming properties.
Steaming milk for a latte or cappuccino
For a latte, you want to produce thick, smooth and creamy milk, not foamy like a bubble bath. You’ll add aeration to produce denser foam for a cappuccino. Well-steamed milk will have a uniform texture, a glossy shine on the surface, and sweet flavor that will support the qualities in your espresso.
Heating milk has another added benefit—heat helps enhance its perceived sweetness. The longer-chain carbohydrates (sugars) naturally present in milk break down into simpler sugars with heat. Just like the difference between refined sugar and wheat, the simpler the carbohydrate is, the easier it is to taste.
Steam doesn’t just add air and heat the milk; the steam jets move milk in the pitcher. By carefully positioning the steam wand, you can use this force to stir in all the great foam. Why is this important? Air is lighter than milk. If left to its own devices, it will float to the surface and form a thick head, almost like a fresh poured lager, which is almost impossible to pour into great latte art. To get the perfect steam wand position, just set your steam wand so it’s slightly off center. You’ll know you’ve hit the sweet spot when the milk spins in the pitcher like a tornado.
What kind of milk should you use
Whole milk works best, but you can adapt these techniques for 2%, skim, or dairy alternatives (soy, almond, coconut, rice). You may have heard skim milk is better for foaming or that whole milk is best for cappuccinos. Both are generally true.
Fat has a destabilizing effect on foam. Remember those unwinding proteins from earlier? The part of milk protein that repels water is as likely to attach to fat as it is to air. It just wants to get as far away from water as possible. The more fat there is in milk, the less air it can hold.
With that in mind, skim milk will yield the most stable and stiff foam. But it’s very hard to use this kind of foam to pour latte art; instead of flowing smoothly out of the pitcher, skim milk tends to “plop” into the cup.
If you want to steam milk for latte art, whole milk tends to produce a creamier, more flavorful foam. Let’s be honest–fat tastes great. It also helps produce a milk foam that is more velvety than dry, as the foam in whole milk is really emulsified air, water and fat.
Quick tips for steaming (and creating art)
• Start with cold milk.
• Purge the steam wand.
• Keep the pitcher straight.
• Partially submerge steam tip about half way between the center and side of the pitcher.
• Introduce air with circular milk motion and a “psst, psst” sound until the pitcher is room temperature (100 degrees Fahrenheit).
• At room temperature, submerge the tip fully and keep the vortex going in the pitcher.
• Keep spinning the milk until the jug becomes too hot to touch, or around 60 degrees Celsius (140 Fahrenheit).
• Turn off the steam and wipe your steam wand with a wet, clean cloth.
• Gently swirl the milk and give the pitcher a couple taps against the counter to remove any large bubbles.
• Pour into wonderful art.
Some pitfalls to watch out for
If your milk gets too hot, the proteins will completely break down, releasing the air and ruining your foam. So it’s important to introduce air before the milk hits room temperature (100°F). After that, it’s much harder to get those air bubbles to turn into a nice, velvety microfoam.
Also, even the best microfoam will eventually collapse because of gravity. Over time, the light air bubbles rise and heavier liquid milk drains from the foam. As the liquid drains, the small bubbles combine into larger and larger bubbles. This continues until the pressure of the air inside the bubble exceeds the strength of proteins holding it in and the bubble pops.
Many “home baristas” like to steam milk before pulling espresso shots and pouring the shots through the steamed milk for freshest, most robust flavor. Problem is the steamed milk starts cooling off and collapsing while you’re creating the shots, so you want to keep the milk as hot as possible. The best solution we’ve seen is to cover your heated latte cup with a Kup Kap cup cover from Koffee Kompanions. Its Thinsulate insulation (by 3M) holds liquids, including steamed milk, at a higher temperature for up to 45 minutes.