Does breast milk curdle?

In this short study, we are going to answer the question ” Does breast milk curdle?” with an in-depth analysis of the factors that promote curdling. Furthermore, we are also going to discuss the methods to curdle the milk.

Does breast milk curdle?

Yes, breast milk can curdle. The breast milk is fresh as long as it is inside the breast but when it is expressed it should be handled carefully because the expressed milk lasts for 3 to 4 hours at room temperature and for 5 days when it is properly stored in the fridge.

What is meant by curdling?

Curdling evolves through the formation of clumps that are formed by the breakdown of colloids or emulsions. Protein is the most important constituent of milk that causes curdling.

How does protein cause curdling?

The protein present in the milk is suspended in a colloidal arrangement with a few protein particles moving around randomly. Normally these protein particles repulse each other and move freely without clumping.

But when the pH of milk changes, particles of protein pull each other and form larger clumps. This is the actual reason behind milk coagulation. 

How can we know that breast milk has gone bad?

●     Milk separates into two layers after the pumping. The fat and protein portion come on the top while the water portion falls to the bottom. If milk is good then it mixes easily when the swirl the bottle gently. But if it has gone bad it remains separated and chunks float over it.

●     You can taste your breast milk to check whether it’s gone bad or not.  If you have refrigerated milk and it is giving a rancid or sour taste then do not give it to your baby and throw it away.

●     You can also check your milk with the sniff test. If your milk smells rancid or sour then it is gone bad. Do not use it.

What factors promote milk curdling?

●     When the pH of milk drops it becomes more acidic and forms more clumps and curdled milk.

●     The curdling of milk takes place more quickly at high temperatures than at low temperatures.

What methods can be used to curdle the milk?

You can curdle the milk by changing its pH or temperature.

Changing the pH by adding acidic substances:

You can curdle the milk faster by adding acidic components like lemon juice or vinegar to it which will lower its pH and form the larger clumps of the protein part of milk.

For this method, warm the milk in a utensil and add acidic substances like lemon juice or vinegar to it. Stir it so that acid mixes with the milk. Leave the mixture for 5 to 7 minutes and then strain the mixture to separate the curd from the mixture. The more the amount of acid you will add, the larger the particles of the curd will form.

Heat the milk for curdling:

For this method, take the milk in the saucepan and leave it on the heat for boiling. Leave it to boil for 1 to 2 minutes after it starts boiling. Stir it occasionally but do not stir frequently because we want clumps of the milk protein. As the temperature reaches 180 degrees Fahrenheit the milk will start curdling.

Remove the saucepan from heat and leave it for 5 to 10 minutes or you can leave it for a longer time for a more curdling effect. Then strain it to get the curd.

Here are some other methods to curdle the milk.

What is the nutritional status of breast milk?

Breast milk is different in nutrition, flavor, and color from regular milk. It is enriched with macro and micronutrients that are required for more pro-growth and development of a baby.

Breast milk contains two types of proteins that are whey protein and casein protein. Whey protein is about 60 to 80% and the remaining portion is casein protein. Breast milk also contains essential fatty acids and vitamins. The main carbohydrate present in breast milk is lactose which accounts for 40%.

How long does breast milk last?

The shelf life of milk varies in different conditions. At room temperature, breast milk can last for 4 to 6 hours. In a refrigerator, it can last ideally for 72 hours but 8 days is also acceptable. In the freezer, it can last for 3 to 6 months whereas in the deep freezer it can last for 6 to 12 months.

How can we store breast milk?

●     In the refrigerator, milk should be kept in the backside away from the door where the temperature is coldest. So that the milk will not be affected by the opening and closing of doors.

●     You can store your milk in commercially made storage bags or plastic or glass bottles for freezing. The containers should be cleaned and properly sealed to avoid any contamination that will cause milk spoilage.


In this short study, we have answered the question ” Does breast milk curdle?” with an in-depth analysis of the factors that promote curdling. Furthermore, we also discussed the methods to curdle the milk.


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