A barista champion’s guide to steaming plant-based milks

Anay Mridul speaks with 2018 UK Barista Champion, Josh Tarlo, about the popularity of plant-based milks and how baristas should be steaming them.

A few years ago, plant-based milks occupied a tiny corner of the coffee industry. Seen as the reserve of vegans and those with lactose intolerance, they carried a substantial surcharge and were largely ignored in favour of dairy.

Today, nearly 60% of UK households purchase plant-based food and beverages, with oat, almond, and soy milks among the most popular products.

To cater to the soaring demand, most coffee shops also keep a wide-ranging stock of plant-based milks to make everything from coconut cold brews to oat milk flat whites.

But in spite of all this, baristas and consumers still bemoan one particular issue with plant-based milks: steaming.

Like with dairy milk, the injection of hot steam and air through a steam wand causes proteins in the milk to encase air and form relatively stable bubbles. When done correctly, this creates a microtextured foam with a creamy, sweet mouthfeel.

However, plant-based milks are particularly susceptible to curdling when added to coffee. When this is added to coffees with high acidity, it can lead to a sour and unpleasant-tasting drink. It can also make latte art a challenge – although some baristas have found ways around it.

“Often, people will put a dash of the cold alternative milk into the espresso before their latte art, as this helps stabilise the acidity,” says Josh Tarlo, who works as head of coffee at UK specialty coffee brand Kiss the Hippo.

“For example, with our homemade nut milk, we tend to see a lot more curdling with it. But I find once you introduce some of the cold milk in espresso, it mitigates quite a chunk of that.”

What is the ideal steaming temperature for plant-based milks?

According to the Specialty Coffee Association (SCA), the ideal temperature for steaming dairy milk is between 55°C and 65°C. Going below this range can lead to “thin”, unstable foam, whereas going above it can end up scorching the milk and ruining the flavour of the coffee.

Due to their makeup, plant-based milks tend to react better to slightly lower temperatures.

“We tend not to go past 55°C (131°F) – but that’s not too hot,” he says. “Above that, you start to ask why, as it will be sitting there for ages before you can drink it.”

Some brands outline specific guidelines recommending the ideal steaming temperature. But Kiss the Hippo isn’t as regimented, letting baristas take the lead by using their experience.

“In terms of coffee quality and consistency, as a barista, you don’t respond well to intense, specific rules that feel like micromanagement,” Josh explains.

He says the company’s baristas adapt temperatures based on location and demographics. For example, the branch in Richmond generally caters to an older crowd, meaning baristas push the limits with heat.

From a scientific viewpoint, Josh explains that as with dairy, slightly cooler steaming temperatures don’t cause sugars to brown. Combined with the lack of curdling, lower temperatures make plant-based milks seem sweeter, which may or may not lend itself to coffee drinks.

“But because you’re never tasting anything in isolation, the harmonisation between the espresso and the milk is better at lower temperatures,” he notes. “However, that might just be because it’s working more together with the actual beverage. Perceived sweetness is a big part of that.”

Modern coffee machines are being designed with plant-based milks in mind. For example, the soon-to-be-launched Heylo Coffee Milk Module features an induction heating system that eliminates the need for steam altogether.

How plant-based milks are shaping the future of coffee

Understandably, a lot has been made about the use of plant-based milk in a coffee industry that’s historically been joined at the hip with cow’s milk.

But despite this, statistics show the market is becoming increasingly lucrative. Globally, plant-based milks accounted for $18 billion in retail sales in 2020, while leading oat milk brand, Oatly, recently went public with a valuation of more than $10 billion.

Kiss the Hippo uses oat milk at its five locations. As a roaster, it has some wholesale customers that are entirely plant-based, and Josh says about 35% of its sales involve plant-based milks.

“Generally, there’s been a massive trend from when Hippo opened its first stores to now,” he says. “I don’t know if it’s been exacerbated by the pandemic, but it’s just more about where the general trend is moving.

“There are a few major trends, including people lessening their impact on the planet through what they eat,” he explains. “The health thing is at play. There’s a cultural perception that milk is way sweeter in terms of topline stuff, so I can easily see [plant-based milks] becoming more popular.”

Because of these consumer trends, milk alternatives aren’t just limited to vegans, but a wider set of consumers who want to shift their consumption habits to care for their bodies and the planet. As the market for these drinks scales up, Josh envisions a future where plant-based milks could be cheaper than dairy – and may even become the default.

Header photo credit: Blackwater Issue