Milk: steaming, frothing and the alternatives

Well-steamed milk is glossy, sweet and pours as a single unified liquid. Badly steamed milk is a layer of hot liquid under a layer of stiff foam.

The difference is technique rather than equipment.

What steaming actually does

Two things happen simultaneously.

Aeration. Air is introduced, and milk proteins stabilise the bubbles.

Texturing. The whirlpool created by the steam wand breaks large bubbles into progressively smaller ones, producing microfoam — a texture so fine it looks like wet paint rather than foam.

Heating also converts some lactose perception, which is why steamed milk tastes sweeter than cold milk.

Above roughly sixty-five to seventy degrees the proteins begin to denature, the texture collapses, and the milk develops a cooked flavour.

Which is why you stop at around sixty degrees.

The technique

Start cold. Cold milk in a cold pitcher gives you more time before it reaches temperature.

Fill to just below the spout base, since the milk will expand.

Purge the wand before and after, every time.

Position the tip just below the surface, slightly off centre, angled to create a whirlpool.

Open the steam fully. Partial steam does not create enough velocity.

Aerate first, for the first few seconds, until you have the volume you want.

You should hear a gentle regular tearing sound, not a loud screech. Loud means the tip is too far out.

Aeration should be finished by around thirty-five degrees. Adding air later produces large unstable bubbles.

Then submerge slightly and let the whirlpool texture the milk for the remainder.

The sound becomes a low hum.

Stop at around sixty degrees — the pitcher becomes uncomfortable to hold, which is a reliable indicator.

Tap and swirl. Tap the pitcher to break any remaining large bubbles, then swirl continuously until you pour.

Swirling keeps the foam and liquid integrated. Milk left standing separates within seconds.

How much air

Depends on the drink.

Flat white: minimal aeration, a thin glossy layer.

Latte: slightly more.

Cappuccino: substantially more, roughly doubling the volume in traditional preparations.

Judge by feel and appearance rather than by counting seconds, since it varies with the machine.

Latte art, briefly

It requires properly textured milk first. No amount of pouring technique rescues stiff foam.

Start with the pitcher high and pour into the centre to sink the milk beneath the crema.

Once the cup is around half full, bring the spout close to the surface and the white will begin to surface.

Then move — wiggle for a rosetta, hold still then pull through for a heart.

Latte art is a byproduct of good texture rather than a goal. A well-textured flat white with no pattern is a better drink than a decorated one with poor milk.

Dairy variables

Whole milk steams most easily. Fat contributes to mouthfeel and stability, and protein does the structural work.

Skimmed milk produces stiffer, drier foam with larger bubbles and less body.

Fresher milk generally steams better. Very fresh milk straight from the fridge is ideal.

Plant milks

They behave differently because their protein and fat content differs, and because they lack the specific protein structures that stabilise dairy foam.

Oat milk has become dominant in cafés because barista formulations steam well and taste sweet and neutral with coffee.

Standard oat milk frequently does not steam well. The barista versions contain added fats, proteins and stabilisers specifically to address this.

Soy milk has the highest protein of the common alternatives and steams reasonably well.

Its main problem is curdling — soy protein coagulates in the presence of acid and heat, so an acidic coffee served hot can separate it.

Adding coffee to milk rather than milk to coffee, and avoiding very hot coffee, both help.

Almond milk is low in protein and steams poorly, producing large unstable bubbles that collapse quickly. Barista versions improve it.

Coconut, rice and other alternatives vary widely and generally steam less well.

The practical guidance: buy barista formulations, steam to a slightly lower temperature since plant milks scorch more readily, and expect the foam to be less stable.

Without a steam wand

Several options produce decent textured milk.

A handheld frother in a jug of warmed milk. A French press — heat the milk, then plunge rapidly twenty or thirty times. An automatic milk frother.

Or simply shake warm milk hard in a sealed jar, which works better than it sounds.

None produce true microfoam. All produce something considerably better than cold milk poured in.

Cleaning

Purge and wipe the wand immediately after every use, before the milk dries.

Dried milk in the wand tip is unhygienic and blocks the holes.

Soak the wand in a milk cleaning solution periodically, and clean the pitcher properly.