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Why Oat Milk Curdles in Your Coffee (and how to Prevent it) 

You’ve likely noticed that oat milk has become ridiculously popular as a plant-based alternative to milk. It has a rich, creamy texture and a natural sweetness that many coffee drinkers love. But those who partake often wonder: Why does oat milk curdle in my coffee?

Yes, a common complaint about oat milk is that it curdles and separates when added to hot coffee. This unintentional curdling leaves an unappealing texture and visual look to the coffee.

There are a few key reasons why oat milk curdles in coffee, primarily having to do with the composition of oat milk combined with the intrinsic properties of coffee itself. 

Understanding what causes oat milk to curdle can help you prevent it from happening. So, let’s take a look at the main reasons oat milk curdles in your coffee and how you can put a stop to it. Then, you can truly enjoy oat milk in your coffee.

3 Main Reasons for Oat Milk Curdling

Oat milk curdles in coffee for three main reasons: 

Coffee Acidity

Coffee itself is acidic. Its caffeine content and other compounds give it a relatively low pH level. And this acidity is one factor that interacts with sensitive proteins in oat milk, causing them to denature and clump together. The proteins then separate, resulting in a layered, curdled look. 

Certain coffee roasts or brewing methods can yield higher acidity levels than others, increasing the likelihood of curdling when mixing with oat milk. 

Try adding oat milk to cold brew coffee, which is less acidic. There are also low-acidity coffee brands like Lifeboost.

Coffee Temperature

Oat milk often curdles in coffee because of the high temperature of freshly made hot coffee.

As with acidity, high heat causes oat milk’s proteins to denature, which alters their shape and exposes reactive parts of the protein. This denaturing allows the proteins to tangle together and curdle out of the smooth solution. 

The hotter your coffee is when you add oat milk, the more likely it is to cause curdling. 

Pouring milk into a cup of coffee

Oat Milk Composition

Finally, the ingredients that make up oat milk itself can impact how prone it is to curdling. Oat milk contains fiber, oil, and proteins that are all sensitive to changes in acidity and temperature. 

The exact protein and fat content can vary across brands, making some oat milks more stable in coffee than others. Homemade oat milk is also usually thinner and watery, providing less stabilizing substances to resist curdling. 

Many store-bought oat milks contain additives like gums, emulsifiers, and stabilizers meant to improve consistency and prevent separation, but the efficacy of these additives can vary.

The Role of Oat Milk Temperature

Checking milk temperature for making coffee

While we’ve covered the importance of coffee temperature in curdling, the initial temperature of the oat milk itself also plays a key role. 

Pouring cold oat milk directly into freshly brewed hot coffee almost guarantees some curdling. The drastic change in temperature shocks the proteins.

Consider these temperature-related tips:

  • Remove your oat milk from the refrigerator well before preparing your coffee. Let your oat milk get to room temperature. This prevents a harsh transition.
  • Heating or steaming oat milk makes it more stable before mixing it with hot coffee. But overheating can also deteriorate proteins, so aim for just warm enough to incorporate microfoam.
  • When first transitioning from dairy milk, oat milk’s propensity to curdle from temperature variations can be frustrating. Experiment with different oat milk brands. With some trial and error, you’ll find the right brand and preparation method to suit your brew.

Getting the temperatures of both coffee and oat milk properly calibrated before combining them goes a long way. Finding the right balance for your personal taste preferences is key to a perfect cup.

Tips to Prevent Oat Milk Curdling

There are a few steps you can take when adding oat milk to coffee to help prevent it from curdling:

  1. Dilute the Coffee: Adding extra water to your cup of coffee right before adding oat milk lowers the acidity and temperature enough to minimize curdling.
  2. Add Steamed/Frothed Oat Milk: Heating and incorporating air into oat milk makes it more stable, so try using steamed or frothed oat milk on top of brewed coffee.
  3. Switch Up Oat Milk Brands: Try a few different brands formulated to be barista-style to see which stands up best to hot coffee without curdling. A good example is Oatly’s Oatmilk Barista Edition. 
  4. Stir Thoroughly Before Drinking: If some curdling does occur, stirring vigorously will re-incorporate and evenly distribute the milk proteins.
  5. Add Salt or Acid: A pinch of salt or a bit of lemon juice raises the pH of the coffee closer to neutral, keeping the milk proteins more stable.
  6. Always Pour Milk Into Coffee: The milk hitting the acidic coffee causes less of a shock than vice versa.
  7. Use Low-Acidity Coffee: Cold brew coffee is less acidic. Or try a low-acidity coffee like Lifeboost. You can also check out this guide on how to make alkaline coffee.

Using one or more of these troubleshooting tips when adding oat milk to your coffee should allow you to enjoy a creamy cup of joe without the unpleasant curdled texture.

The Final Scoop

Many coffee lovers have embraced oat milk as a favorite plant-based milk alternative that makes morning coffee feel like a luxurious, creamy treat. But dealing with curdled blobs floating on top of your otherwise perfect coffee is decidedly unpleasant. 

Now that you understand the science behind why oat milk curdle -, mainly the acidity, temperature, and sensitivity of proteins – you can take steps to prevent it. 

Diluting and cooling coffee before adding oat milk, heating or frothing the oat milk itself beforehand, and thoroughly stirring the final drink provide simple solutions. Finding just the right oat milk brand and brewing method can also minimize curdling issues. 

With the right preparation tricks, oat milk and coffee can live together in perfect harmony without unwanted curdling.

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