Cold Foam: How to Make It at Home, and Why Skimmed Milk Works Best

Cold foam is milk frothed without heat and spooned over iced coffee or cold brew. To make it, froth about 80 ml of cold skimmed milk — with a teaspoon or two of syrup if you like — for 15–30 seconds with a handheld frother or a French press, until it has thickened and grown by about a quarter to a third, then pour it gently over the drink.

It solves an old problem with cold coffee: you could not put foam on it. Hot foam melts the ice and sinks; steamed milk is the wrong temperature. Cold foam is the same idea as a cappuccino's cap, made at fridge temperature.

The recipe

1. Put the cold milk and syrup in a tall jug or the beaker of a French press.
2. Froth. Hold a handheld frother just below the surface, or pump a French press 20–30 times. Arla Foods' barista guide suggests that around 15–20 seconds with a frother or steam wand is enough, and warns against over-foaming: you need surprisingly little foam on an iced drink.
3. Tap the jug on the counter to burst any large bubbles.
4. Spoon or pour it on at the end, over the finished drink.

If you use a steam wand, Arla's advice is to aerate for only a few seconds and stop before the jug feels warm, so the milk stays cold enough not to melt the ice.

Why skimmed milk foams best cold

Starbucks, which popularised cold foam, launched it in April 2018 made from aerated skimmed milk, after several years of development. Trade reports at the time explained the choice: the foam stays stiff in the cup because of its lower fat content.

Dairy science says the same. Foam in milk is built by proteins, which unfold at the surface of each air bubble and form a film around it. Fat works against them. A 2010 review of milk foaming in the International Journal of Dairy Technology found that skimmed-milk foams can be extremely stable, and that milk fat is particularly damaging to foam formation and stability at temperatures where the fat is partly solid — the review gives 20 °C as an example. Fat gets in the way of that protein structure, and the review found it does the most damage when it is partly solid.

That is the opposite of hot steaming, where the fat has melted and whole milk makes a rich, creamy microfoam. Cold, the fat is a liability. So:

• Skimmed milk makes the stiffest, longest-lasting cold foam.
• Semi-skimmed works, with a softer foam.
• Whole milk foams cold, but the foam is looser and collapses sooner.

Vanilla sweet cream foam: the fat-rich alternative

Café menus also offer a richer version made with cream. Starbucks' sweet cream is a mix of 2% milk, heavy whipping cream and vanilla syrup, and frothing a similar mixture gives a sweet cream cold foam. It works by a different mechanism altogether.

Whipped cream gets its structure from fat, not protein. In cream with enough fat — typically 30–36% — whipping knocks fat globules into each other until they partly merge into a network that traps the air, and the cream roughly doubles in volume. Milk and low-fat cream, as Wikipedia's summary of the science puts it, do not have enough fat to whip effectively.

Sweet cream foam sits deliberately between the two. Run the numbers for a common home recipe of 2 tablespoons of heavy cream, 1 tablespoon of 2% milk and 1 tablespoon of vanilla syrup, using USDA figures of 36% fat for heavy cream and 2% for the milk:

• Cream and milk alone: about 11 g of fat in 45 g, or about 25% fat.
• With the syrup: about 11 g of fat in roughly 63 g, or about 18% fat.

Both are below the roughly 30% that cream needs to whip into peaks. So instead of stiffening into whipped cream, the mixture thickens into a dense, pourable foam that floats on cold brew and slowly drifts down through it. Froth it until it is thick and ribbony, and stop before it holds a shape; if you keep going, it becomes whipped cream.

Tools

Electric milk frothers with a cold setting also work. As Arla's guide notes, foam from these devices often looks thicker than it feels to drink, so you can let it run slightly past your target.

Using it

Cold foam goes on last. Pour it over a finished drink — cold brew, an iced latte, an iced americano or a nitro cold brew — and drink through it rather than stirring it in. Flavour it in the jug, not in the cup: a teaspoon of vanilla or brown sugar syrup, a pinch of cinnamon, or a spoonful of cocoa for a chocolate foam.

On calories, plain foam is almost nothing. At the USDA's 34 kcal per 100 g of skimmed milk, 80 ml comes to about 27 kcal, and only part of it may end up on the drink. A sweet cream foam is a different matter: two tablespoons of heavy cream at 340 kcal per 100 g are about 100 kcal on their own, and with the milk and a tablespoon of syrup the topping comes to roughly 140 kcal.

For the hot equivalent, see the steaming guide.