Do you love the taste of coffee but can't stand the way soy milk curdles in it? If so, you're not alone. Soy milk curdling is a common problem for coffee drinkers who switch from cow's milk to plant-based milk alternatives.

While several factors contribute to soy milk curdling, there are also several ways to prevent it. In this blog post, we will explore why does Soy Milk curdle in coffee and offer tips on how to prevent it from happening!

What is Soy Milk

Soy milk was first created in China over 2000 years ago. Today, it is consumed all over the world and is made in many different countries. The three leading producers of soy milk are the United States, Brazil, and China.

Soy milk is made from soybeans that have been soaked and ground in water. The resulting mixture is then strained to remove any solids. Soy milk has a similar consistency to cow's milk and can be used in the same way.

It is often used as a dairy-free alternative for those who are lactose intolerant or have dairy allergies. Soy milk can also be used to make vegan cheese, yogurt, and ice cream. Additionally, soy milk can be used as a coffee creamer or added to loose leaf tea.

Soy Curdle in Coffee

Why Soy Milk Curdle in Coffee? - Real Reason

Two main factors contribute to soy milk curdling in coffee: acidity and temperature.

1. Acidity is the First Reason

Coffee is an acidic beverage. The acidity level of coffee beans varies depending on the type of coffee bean and where it was grown. Arabica beans, for example, tend to be less acidic than Robusta beans. The roast level of the bean also affects its acidity; darker roasts are typically less acidic than lighter roasts.

When coffee is brewed, the resulting liquid has a pH between four and five. This means that coffee is more acidic than milk (which has a pH of around six). When soy milk is added to coffee, the combination can become even more acidic. This can cause the proteins in soy milk to curdle.

2. Temperature is the Second Reason

The second factor that contributes to soy milk curdling is temperature. Soy milk is typically heated to around 155 degrees Fahrenheit when it is produced. When soy milk is added to hot coffee, the temperature of the milk rises quickly.

If the temperature of the milk gets too high, it can cause the proteins to denature (or change shape). This can also lead to curdling.

Prevent Soy from Curdling

3 Ways to Prevent Soy Milk from Curdling

There are several ways that you can prevent soy milk from curdling in your coffee.

1. Choose the Right Coffee Beans

As we mentioned earlier, different types of coffee beans have different acidity levels. If you find that your soy milk will curdle frequently, try switching to a less acidic bean.

Arabica beans are a good option to try. You can also experiment with different roasts to see if that makes a difference.

2. Use the Right Grind Size

The grind size of your coffee beans can also affect the acidity of your coffee. If you're using pre-ground coffee, make sure that the grind size is appropriate for your brewing method.

Coarsely ground beans are best for French presses, while finely ground beans are better for drip coffee makers.

If you're grinding your own beans, we recommend starting with a medium grind. You can always adjust the grind size based on how your coffee tastes.

3. Let Your Coffee Cool Before Adding Soy Milk

One easy way to prevent soy milk from curdling is to let your coffee cool for a few minutes before adding the milk. This will lower the temperature of the coffee and reduce the chance of curdling.

If you can't wait for your coffee to cool, you can also try slowly adding the coffee to the soy milk. Pour a small amount of coffee into the milk and whisk quickly to combine. Repeat this process until all of the coffee has been added.

These three tips should help you enjoy soy milk in your coffee without worrying about curdling! If you have any other questions about brewing coffee with soy milk, feel free to reach out to us. We're always happy to help!


There you have it! These tips should help you enjoy soy milk in your coffee without worrying about curdling. If you have any other questions about brewing coffee with soy milk, feel free to reach out to us. We're always happy to help! Happy coffee drinking!

Author: Richard Smith

Partner at The Kent and Sussex Tea and Coffee Company

Richard Smith is a Tea expert, entrepreneur, and owner of The Kent and Sussex Tea and Coffee Company. Part of a family of renowned Tea planters dating back four generations, he was born in Calcutta (Kolkata), India, where he spent his childhood between Tea Estates in Assam and Darjeeling.

In the late 1970s, having accumulated years of knowledge in the industry, Mr Smith and his mother, Janet Smith, moved to Kent, South East England, to establish a Tea business in the village of Pluckley. Their early days of packing Tea Bags by hand from chests of 10,000 prompted the creation of the company’s flagship infusion known as Pluckley Tea. It remains our most popular product today.

Mr Smith, who studied economics at London Polytechnic, has since specialised in over 1,000 types of Loose Leaf Tea - in addition to around 70 varieties of Roast Coffee - from around the world. These are now available at The Kent and Sussex Tea and Coffee Company, where everything is still packed by hand and fresh to order, not only to honour tradition but to ensure the utmost quality and consistency.