Non-dairy kinds of milk are common additions to that morning cup of Joe, but why does oat milk curdle in coffee? Let’s take a closer look.
When it comes to a non-dairy alternative for coffee, oat milk is one of my go-to options. It’s got a smooth, creamy texture, and it tastes a lot like regular cow’s milk.
But it can sometimes curdle, especially when mixing it with hot coffee.
The main reasons why oat milk curdles have to do with the relatively high level of acidity in coffee, along with the temperature. And the hotter the beverage, the higher the likelihood of curdling.
In this article, I’ll reveal what specifically causes oat milk to curdle in coffee, and what you can do to help prevent it.
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What causes oat milk to curdle in coffee?
To answer this, we first need to look at the science behind acidity and temperature.
Acidity
In order to address the acidity question, let’s take a look at how the pH scale works. pH measures the acidity levels in a given substance, from a range of 0-14.
Items below 7 signal acidity. Those above are considered to be a base. But back to the oat milk and coffee!
Oat milk itself is mildly acidic, falling somewhere between 5-6 on the pH scale. But the acidity of coffee is slightly greater, with a level hovering about a point lower on the scale.
When the oat milk comes in contact with the coffee, this can trigger a chemical process that raises the acidity level of the milk. This causes other components to separate from the water in oat milk and create distinct clumps — or curdle.
Temperature
Higher temperatures, like those found in a hot cup of coffee, can also contribute to the curdling of oat milk.
That’s because oat milk is essentially an emulsified product consisting of proteins, fats, and water. When it’s exposed to heat, the emulsion can break down. Then the oat milk separates and curdles.
The higher the heat of the coffee, the more likely the oat milk will curdle, so you want to avoid adding it to very hot coffee — or heating it on its own.
👉🏼 Related: Can You Freeze Oat Milk?
How to keep oat milk from curdling in coffee
The good news is that there are several steps you can take to help make sure your oat milk doesn’t curdle in your coffee.
Use fresh milk
Older oat milk — or worse spoiled milk — is more likely to clump and curdle.
After you open the carton, you need to refrigerate it. And it’s best to consume oat milk within 7-10 days after opening. After that, lactic acid levels can rise in the milk, which can make it start to separate and eventually spoil.
Sings of spoilage in oat milk include sour or rancid odors, yellowish discoloration, and clumping. But even if it’s not past its expiration date, it can still start to separate if was opened several days earlier.
So for best results use fresh oat milk. And it’s a good idea to check it before adding it to your coffee.
Don’t use very hot coffee, and warm up the milk
Wait for the temperature of the coffee to cool down a bit after brewing so it’s not overly hot. Then heat up the oat milk so it’s warm but not hot; somewhere around 150° F. The idea is to get both beverages to have similar temperatures, in order to reduce the risk of the chemical reactions that can cause the oat milk to curdle.
Add the oat milk first, then the coffee
If you don’t have time to heat up your oat milk, try adding it to the coffee mug or cup while your coffee is brewing. This will allow the milk to at least come up closer to room temperature rather than adding cold milk directly from the fridge.
Use coffee with lower acidity
Choosing coffee beans that are lower in acid can lessen the chances of causing curdling with oat milk.
Avoid using coffee made with Arabica beans, or ones with light or medium roasts for example, as those are high in acidity.
Instead, opt for dark roast coffees or espresso roast. They use longer roast times for the beans, which breaks down the acid in them and makes either one a good option to help reduce unintentional curdling.
Use barista oat milk
You may wonder why oat milk that you get mixed in with drinks from your favorite coffee shops don’t curdle. That’s because there are several different brands of so-called “barista” oat milks that are more stable and made to withstand high temperature and acidity.
Some of these oat milk brands include:
Try oat milk enriched with calcium
Some kinds of oat milk feature extra calcium, an alkaline which can help neutralize acids. So calcium-enriched oat milk can stand up to acidic coffee better than regular milk can, lowering the chances of curdling.
Does oat milk curdle in coffee more easily than other types of milk?
All plant-based milk, including soy milk, almond milk, and coconut milk — as well as cow’s milk — can all curdle in coffee. Unlike oat milk, those other types are not acidic, however coffee’s acidity can still lead to curdling regardless of the type of milk. In addition, exposure to very hot coffee can also cause curdling in various kinds of milk.
FAQ
Store-bought oat milk generally has a shelf life of between 7-10 days after opening. Once it is opened, it must be kept in the fridge in order to prevent spoiling. Homemade oat milk can keep for up to 5 days if kept in an airtight container in the refrigerator. Do not leave oat milk out at room temperature for more than 2 hours, or harmful bacteria could start to form in it.
If your oat milk has curdled due to mixing it with the coffee alone, then it’s typically safe to consume. And it won’t affect the taste of the coffee or the milk. However, if it’s curdled due to spoiling, then avoid drinking it, as that could carry a risk of food poisoning.
More non-dairy milk answers
Get more answers to your questions about non-dairy cow’s milk alternatives. Check out these posts.
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