Why Does Oat Milk Curdle In Coffee? (+ How To Prevent It)

If you’re wondering “why does oat milk curdle in coffee?”, you’ve come to the right place.  We’re exploring why this happens, how to prevent it and which brands of oat milk are the best for use in coffee.

Oat milk has quickly become a favourite among vegans and coffee enthusiasts, thanks to its creamy flavour and smooth texture. However, many have encountered this frustrating issue; oat milk separating in coffee.

In this article, we’ll explore why oat milk curdles in coffee and how to prevent it.

*Hint* Brand and type of oat milk makes a big difference, so we’ll also be revealing our favourite oat milk brands for a silky smooth morning coffee!

Quick Links:

• What is curdling?
• Why does oat milk curdle in coffee?
• How to prevent oat milk from separating in coffee
• The best oat milk for coffee
• The best oat milk for iced coffee
• The best oat milk for frothing

What is curdling?

Curdling is a chemical reaction that occurs when the proteins in the non-dairy milk separate from the liquid.  This results in a liquid with small lumps (or curds) floating around in it.

Curdled oat milk is not very pleasant in your morning cup of coffee!

Is it normal for oat milk to curdle in coffee?

It can be somewhat common for oat milk to separate in coffee, for reasons we will outline below. However, some brands of oat milk are more prone to curdling than others.

This doesn’t just happen with oat milk, it can also occur with other plant-based milk alternatives from almond milk, rice milk and soya milk to hemp milk, cashew milk and coconut milk.

Check out our section ‘the best oat milks for coffee’ to find out which oat milk brands faired the best in our coffee tests.

Why does oat milk curdle in coffee?

So, why does oat milk separate in coffee?  Oat milk separates in coffee for two main reasons:

1. The acidity. Coffee is naturally acidic whereas oat milk tends to have a more neutral PH. When the oat milk is introduced to the acidic coffee, this difference in acidity can cause the proteins in the oat milk to separate from the liquid; thus causing it to curdle.
2. The temperature. Hot coffee can shock the cold oat milk, causing it to separate and curdle. This tends to happen more so if the oat milk is refrigerated since the temperature difference is greater.

Oat milk brand Oatly also states that “hard water (such as mineral water that contains high calcium and magnesium ions) can also affect the stability” of oat milk.

You may also be wondering… why does oat milk curdle in iced coffee?  Well, it’s for much the same reasons; the acidity difference between the coffee and milk, but also the temperature shock of adding ice to the milk.

Why do some brands of oat milk curdle more than others?

Barista-style oat milks are specifically formulated to be more stable in coffee, often containing added oils and stabilisers to prevent separation during use.

Organic, or more natural oat milk types, often contain just two or three ingredients with no added ingredients to help prevent separation. This is why you’ll typically find the barista-style oat milks will hold up better in coffee, whilst some of the organic varieties or homemade oat milk recipes may curdle more easily.

How to keep oat milk from separating in coffee

Here are our tips for preventing oat milk from separating in coffee:

1. Pick a barista-style milk

This is the most important tip because the brand and type of plant milk can make all the difference. Barista-style milks are specifically formulated to be more stable in coffee.  So, if you want to avoid your oat milk separating in coffee, switching brands is the first step!

(If you’ve got non-barista oat milk to use up, fear not, we’ve got some more tips for you to try)

2. Warm the oat milk first

Before pouring oat milk into your coffee, gently warm it to around 60°C (140°F), or at the very least bring it to room temperature. This minimises the temperature difference between the cold milk and the hot coffee, which reduces the likelihood of curdling.

You can warm the milk on the hob, in the microwave or using a milk warmer and frother like the one linked, which warms the milk gently whilst frothing it at the same time.

Note on organic oat milks.  Oat milk brand Oatly recommends heating organic oat milk versions to just less than 60°C / 140°F, so opt for around 55°C / 131°F if you’re using organic oat milk.

Warm not hot. Be careful not to let the milk get too hot, because the high heat can also cause it to split!

3. Pick a low acidity coffee

You may find a coffee that is specifically labelled as low-acidity, but if not, opt for a darker roast coffee. Light and medium roast coffees with fruity flavours tend to be more acidic than dark roast coffees.

Over-extraction can increase the acidity of the coffee.  Avoid over-extracting your coffee by shortening brew time and ensuring your water is between 90°C to 96°C (195°F to 205°F).

4. Pour slowly

When adding oat milk to a hot cup of coffee, pour it in slowly, whilst stirring continuously. This gradual mixing helps to reduce the shock of the oat milk combining with the coffee.

5. Higher fat content

If you cannot find barista-style milk in your local store, opt for the oat milk with the highest fat content. Fat can help to stabilise the milk, which is why you will often find oils added to oat milk.

Does oat milk need to be refrigerated?

Yes, oat milk should be refrigerated once opened, even if it is a shelf-stable variety. Refrigeration helps to preserve the freshness of the milk and prevents spoilage.

Always follow the directions on the carton of the oat milk you have purchased, but generally, oat milk will last around 7 days in the refrigerator.

Unopened shelf-stable oat milk should be kept in a cool, dark place away from direct sunlight. Unopened fresh oat milk (from the chilled section of the supermarket) should always be kept in the fridge.

If your oat milk has been improperly stored (e.g. not refrigerated after opening, stored somewhere too warm or kept past its best before date), this can cause it to curdle before you use it in your coffee or hot beverages.  You should not use spoiled oat milk.

Does oat milk froth?

Yes, oat milk can froth… but it does depend on the type.

How well an oat milk froths depends on the milk’s protein and fat content, as well as the presence of stabilisers.

Barista-style oat milks have usually been designed to froth well, using the addition of oils and stabilisers to create a thick, stable foam.

On the other hand, organic or more natural oat milks, which often contain just a few simple ingredients such as oats and water, tend not to froth as well. The bubbles tend to be bigger and do not hold their form in the style of a thick cappuccino foam.

To froth oat milk, you can use the steam wand on your coffee machine or an electric milk frother (like the one linked). Ideally froth oat milk from chilled, gradually heating it for the best results. The quality of the foam you achieve will vary depending on the brand and type of oat milk that you use.

Head to the next section to find out ‘the best oat milk for frothing’.

The Best Oat Milks

The best oat milk for coffee

If you’re looking for a great all-around oat milk for your daily coffee, whether it’s hot or cold, a cappuccino or a latte, here are our top picks:

1. Oatly Oat Drink Barista Edition: Oatly Barista is consistently ranked as one of the best oat milks for coffee and other hot drinks. It’s deliciously creamy and has a silky fullness to it, where others can be watery and lacking. It froths like a dream and despite using it on a daily basis in all varieties of coffee – we’ve never had it split.

Note: Opt for the non-organic Oatly Barista version if you’re looking for a more stable oat milk, because the organic version does split on occasion.

2. Minor Figures Barista Oat: Another top performer, Minor Figures Barista mixes smoothly with hot coffee. With a creamy texture and neutral flavour that doesn’t take away from the coffee flavour, it’s a great choice for those who are used to cow’s milk. It doesn’t froth quite as well as Oatly Barista though.

3. Alpro Barista Oat: A solid choice for your morning coffee, this creamy oat milk mixes well with coffee and rarely curdles. It froths beautifully too, if that’s your thing! It doesn’t seem quite as ‘full’ when mixed into coffee as the Oatly Barista though – more of a semi-skimmed than a whole milk.

The best oat milk for iced coffee

Iced coffee can present additional challenges for oat milk, as the cold temperature can sometimes cause curdling or separation.  To avoid this, it’s important to choose an oat milk that has been specially formulated for use in coffee, such as a Barista variety.

These are some of the best oat milks for iced coffee, in our opinion:

1. Oatly Oat Drink Barista Edition: If you’re looking for a rich, creamy iced coffee, Oatly Barista will be your top choice. It’s slightly thicker and creamier than some of the other oat milks on the market, which gives it more of a ‘whole’ milk texture.  It mixes well and we’ve never had it separate.

2. Califa Farms Oat Barista: A great choice for iced coffee, this Barista blend is smooth, creamy and doesn’t tend to curdle when mixed with cold or hot coffee.

3. Minor Figures Barista Oat: A popular choice for iced coffee, this oat milk has a creamy consistency and neutral oat milk taste that lets the coffee flavour shine through. It mixes well with iced coffee and tastes great.

We’ve got a simple recipe for Oat Milk Iced Coffee, if you’d like it!  Click here.

The best oat milk for frothing

If you love a coffee mug full of frothy coffee or a bit of latte art, try one of these oat milks:

1. Oatly Oat Drink Barista Edition: Froths. Like. A. Dream. It’s thick, velvety and holds its form. Oatly Barista creates a seriously lovely Cappuccino!

2. Alpro Barista Oat: This oat milk froths so well that you’ll regularly see it being used in big coffee chains. It produces a wonderful, thick, silky smooth foam that’s perfect in coffee.

3. Cailfa Farms Oat Barista: Califa Farms is one of the top-rated oat milks; it has a beautiful creamy flavour and froths very nicely indeed. It produces a lighter foam than the Oatly Barista, which some may prefer.

I hope you’ve found this article helpful!

If you came here wondering ‘why does oat milk curdle in coffee?’, I hope we’ve answered your question, along with giving you tips to prevent it from happening.

Ultimately, the most important thing is to pick the right kind of oat milk, but also following our tips for how to keep oat milk from curdling in coffee can also help.

Whether your coffee of choice is a frothy cappuccino, an iced latte or just a good ol’ cup of milky coffee, there’s an oat milk out there that is perfect for your needs.

Just remember – store your oat milk properly, experiment with different brands until you find your favourite and enjoy the process of finding the perfect oat milk for your coffee.

Love coffee? Here are some vegan coffee treats you may enjoy:

Espresso Martini Cookies

Biscoff Tiramisu

Pumpkin Spice Latte

If you’d like delicious vegan recipes delivered to your inbox, be sure to subscribe to the A Vegan Visit newsletter. We’d also love for you to join the AVV community on Youtube, Tiktok, Instagram, Pinterest and Facebook.

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