Cappuccinos, lattes, macchiatos, flat whites… milk-based coffee consists of nothing more than exactly that: milk and coffee. But steaming milk varies significantly from cup to cup.
Here’s what you need to know about milk steaming.
A good microfoam is like wet paint. It’s velvety and silky smooth. It’s dense and contains little to no air, making it the perfect milk for pouring deep into a cup to produce striking latte art.
Steamed milk uses pressurised steam to heat the milk up and develop a texture at the same time. To get nerdy about it: steamed milk heats up the sugars in milk and breaks down the fat. As the steaming process occurs, air bubbles form within the milk on a uniform basis, making a layer of microfoam that creates that silky texture.
How to make microfoam
To create microfoam, place your steam wand in the milk and turn it on. You’ll want to generate a whirlwind effect for the milk, and you’ll want to keep one hand on your milk jug to gauge temperature effectively. Oftentimes, overheated milk will mean more air in your milk, and consequently, less velvety milk.
It’s this microfoam that means baristas can pour a balanced and even coffee, producing pretty patterns, rosettas and hearts alike.
Understanding foamed milk
Foamed milk (or frothed milk) follows the same practice as microfoam, except when you steam milk, you inject a lot more air, which gives the milk a light, delicate and bubbly texture.
How to froth milk
To froth milk properly, place the tip of your steam wand just above the surface of your milk and turn on. You’ll want to create a whirlwind effect like when you produce microfoam, except this time, you want to consistently inject air into your milk until the milk jug reaches a point too hot to hold. You need less milk in your jug when steaming foamed milk because the air will naturally expand your milk and add volume, so be mindful of how much you use.
Milk temperature is a tricky one, and there are many factors at play, but it is arguably the most important factor to consider when steaming milk; it’ll make or break your texture, flavour and density. Too hot, and you’ll be left with a velvety smooth texture. Too cold, and you’ll have wet and ‘soggy’ milk (and complaining customers).
Understanding the right temperature of milk is variable to the brand and quality of milk you use. For example, whole milk will contain more fat and consequently, it’ll require a longer period of time to heat, but there are some benchmarks to take into account.
For example, regular cow’s milk consists of two types of proteins: Caseins (which accounts for about 80 percent of the milk) and whey proteins (which makes up the remaining 20 percent). Coffee experts suggest that steamed or frothed milk should ideally sit between the 140-160 Fahrenheit bracket.
However, many specialty coffee shops will steam their milk at a lower temperature to preserve texture and flavour, and many commercial chains will steam their milk a lot higher because, well…
The truth is, there is no definitive answer to milk temperature. It’s as much about personal choice as it is about quality.
Milk steaming will make or break a coffee
Although there are rules to follow to produce good-quality espresso beverages, many coffee shops fail to truly understand how to make microfoam, and as a result, they end up sacrificing on quality.
Foamed milk is arguably easier to produce than microfoam. It requires less control and precision over air injection. Consequently, the risk of ruining foamed milk is minimised. Microfoam, then, requires more accuracy to perfect, and it can be easily tarnished, but the reward massively outweighs the risk of a mistake, because there’s nothing quite like a velvety smooth cup of coffee.