How do you curdle Milk? (1 Common Method)

In this brief guide, we will answer the question, ‘ How do you curdle milk?’. We will study the process that makes milk curdle and ways to tune the procedure according to our demand.

How do you curdle milk?

Milk curdles as it undergoes a chemical reaction. The milk curdling process causes the milk to change its texture. As a result of milk curdling, dairy foods were produced. Structural changes to the milk let us have, cream, cheese, and yogurt.

The main constituent of milk is called ‘casein’ which is the milk protein. The proteins are in suspension as small molecules, which sometimes clump together. In normal conditions, the proteins repel each other but, certain conditions can cause them to come together. A change of pH and a warm temperature encourages the proteins to coagulate.

An acidic element is added to milk and a warm temperature to make the milk curdle.

Spoiled milk also undergoes the same curdling process. Bacteria digest the lactose milk sugar and change it to lactic acid. 

As lactic acid produces, the pH drops. The nature of milk has now turned acidic. Consequently, the protein clumping process starts.

If you deliberately want to induce the curdling process, you can do so by adding a curdling agent. Lemon juice and vinegar both work well. Their acidic nature hastens the curdling process. However, you also need to heat the milk to encourage the coagulation process. Otherwise, the coagulation process occurs very slowly.

Lemon contains citric acid that causes the lemon juice to have a pH of around 2, while the acid found in vinegar is acetic acid that causes the pH of vinegar to be 2.5.


Let us look at the methods that will easily let you curdle milk:

Method 1 – Cheese from Curdled Milk

Pour your milk into a saucepan and heat it at medium flame.

When the milk starts to simmer, add the acid. You can add a few spoonfuls. The more you add, the larger the clumps form. The quantity of acid also impacts the speed of the curdling process.

After you bring the pan off the heat, let it sit for a few minutes and let the curds develop. It will take 5-10 minutes for your curds to form; if they don’t, you can return the pan to heat.

You can separate the whey from the curdled solids now. Strain the whey using a cheesecloth or a muslin. The liquid way is a by-product with plenty of uses and nutrients. The curdled part that you get is cheese.

You can now press the curdles together to form a lump of cheese. If you like, you are free to use the suspended curdles instead of cheese.

The whey is also used as a cooking liquid or a flavoring agent. Whey is also a good source of proteins. 

Acid set cheese or curdled cheese is a product of acidification of milk. In curdled cheese, the starter enzyme called rennet is absent. Curdled cheeses produce paneer, ricotta, and cottage.

How to make buttermilk by curdling milk?

If you do not heat the milk before you add acid, you will end up with buttermilk. Buttermilk forms after acidification of milk at a cool environmental temperature. The curdle formation is too slow to produce cheese.

The coagulates are too fine to be visible here. However, they are in suspension in the liquid whey. The tangy and sweet taste of the liquid that you know as buttermilk

Method 2- Yogurt from milk 

Heat the milk 180 degrees to allow the undesirable bacteria to die.

Let the milk cool before you introduce the yogurt starter. You can buy a starter mix such as Yogourmet. Alternatively, you can use a few spoons of premade yogurt as a starter.

Now cover your yogurt bowl and let it sit in a warm environment for 8 hours.

As the incubation process proceeds, the milk texture becomes thicker. 

You can also put it in the refrigerator for a few hours to let the yogurt set. 

Other FAQs about Milk which you may be interested in.

How long almond milk lasts after opened?

How long can I leave milk out?

How to use condensed milk in place of milk?

Why does the fermentation process produce yogurt?

The starter culture added to milk encourages yogurt to churn out, has beneficial bacteria that cause curdling; Lactobacillus Balgaricus and streptococcus thermophilus.

The bacteria respire and reproduce and produce lactic acid as a result. Lactic acid forces the proteins to coagulate and hence cause the thickening. 

Can yogurt curdle?

Besides milk, yogurt can also curdle. When yogurt curdles, the whey and the proteins separate. The onset of yogurt curdling is a result of a large quantity of yogurt starter. Yogurt curdles when heated to a high temperature. Vinegar or lemon can also make the yogurt curdle.

In this brief guide, we answered the question, ‘ How do you curdle milk?’. We studied the process that makes milk curdle and ways to tune the procedure according to our demand.


Hi, I am Charlotte, I love cooking and in my previous life, I was a chef. I bring some of my experience to the recipes on this hub and answer your food questions.