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Does Oat Milk Curdle In Coffee? (Why & How To Stop It)

The short answer is yes, oat milk can curdle and separate when put into coffee.

First, why put milk in coffee?

People often opt to put milk in their coffee because the taste can be quite sour.

For the past few years, lactose-free products have become quite popular, providing options for those who are unable to handle the lactic contents of milk.

Recently, there has been an uptick in the use of oat milk in addition to other alternatives to cow’s milk.

One of the downsides to using oat milk and some plant-based milk alternatives, is that it can be a little unstable when mixing with coffee.

Why does Oat Milk Curdle in Coffee?

There are a few reasons that oat milk curdles in coffee.

But there is one main reason this happen –

Acidity of Coffee

There are a few acids present in your average coffee cup, including phosphoric, linoleic, palmitic, quinic, chlorogenic, citric, acetic, lactic, and malic acid.

Citric and malic acid can be processed.

The acidity present in your coffee is correlated with the roasting and brewing process it undergoes.

On the PH scale of acidity, coffee can present with a PH lower than 5, which causes a separation of the fat and liquid within the oat milk.

This does not happen with cow’s milk because regular milk contains mineral phosphates which don’t disregulate when introduced to acidity. 

A breakdown of the acids present in coffee:

  • Citric Acids: this acid is present mostly in green coffee and is most subdued while it undergoes the roasting process.
  • Malic Acid: It is tart and its acidity tends to stay despite its brewing and roasting methods.
  • Acetic Acid: this acid presents itself during the processing and roasting process. This does not taste good in large quantities. 
  • Lactic Acid: This acid gives the coffee a lush, creamy feel and look.

What is oat milk?

Oat milk is more oat water than is “milk”.

It is made by mixing oats with water where the oat brans are removed and the liquid base remaining is what we call “oak milk”.

This can be made fresh at home with minimal equipment.

Some make it at home using cheese cloth to separate the oats from the liquid that is remaining.

There are also some that can be found at a local grocery store.

There are many brands and can be used for different reasons.

For example, Oatley has a barista edition that is meant to handle the temperature changes that cause curdling in more unstable oat milks and even adds a foaming effect.

However, there are still cases where curdling happens – let’s take a look at what factors cause curdling/ separation in oat milk below. 

Temperature Regulation and Oat Milk 

Oat milk is a substance that can be easily disregulated, and responds best to gradual changes.

Depending on the temperature of your coffee, this can also cause it to look curdled when mixed with your coffee, even if it is not spoiled.

There are brands of oat milk that contain acidity regulators which prevent the oat milk from breaking down in the coffee. 

What does curdling indicate? 

It is also possible that curdling is an indication that your oat milk is spoiled, especially if you see that it is tinted yellow or has a taste that is very tart, although it is not dangerous – it may be best to purchase or make a fresh batch of oat milk.

One way of prolonging the life of your oat milk is to freeze it. 

How to prevent curdling coffee?

In terms of coffee, if you are able to select coffee that is low in acidity, this will assist in keeping your oat milk intact.

A smaller bean, and also some roast/brew combinations can allow for lower acidity in your coffee.

There are even some additional benefits to the low acidity of coffee outside of its effect on oat milk.

Low acidity coffee is better for the long term health and strength of your teeth and may help with gastrointestinal issues that commonly arise from coffee. 

Organic No Acid, or Low Acid Coffee Beans:

The processing method for coffee beans can determine their acidity.

There have been studies that prove that washed coffee beans have higher levels of acidity.

If you purchase naturally processed coffee, it has a higher sweetness. 

Dark-Roasted Coffee:

Roasting coffee helps the acids break down. Coffee that is dark roasted can be low in acidity and may be a very good option if you are searching for a low-acid option. 

Brewing Method:

Coffee that is cold brewed has lower acidity compared to hot brewed coffee.

Different temperatures can cause particles that dull acid in coffee to be extracted.

Cold brewed coffee is less bitter and less acid than hot brewed – so if you are having trouble with your oat milk due to acidity, and are not particular about how your coffee is brewed, this may be a great option. 

Heat up the Oat Milk

You can heat up the oat milk for a few seconds in the microwave to lessen the contrast between the oat milk and coffee mixture. 

Another way of gradually raising the temperature without separation, is to first pour the oat milk into your cup, and slowly pour the coffee into the oat milk.

This will allow for the oat milk to gradually work up to the temperature of the coffee and prevent curdling. 

Use Oat Milk Emulsifier:

Some oat milk brands utilize oils to help make oat milk thick and creamy.

When the oil is added, it needs an emulsifier to stabilize the milk and prevent separation.  

Use Natural Oat MIlk

If you use fresh oat milk that has not been placed in the refrigerator, this can often be the best option to reduce thermal issues and other factors that induce curdling. 

In conclusion, there are many methods to reduce the natural separation or curdling effect that can occur with oat milk when mixed with coffee.

Each of these methods can be helpful in making a great cup of coffee with oat milk. 

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