Why Does Milk Curdle Heres What We Found Out

When you’re a kid, your mom or dad might tell you that milk curdles when it gets cold — and then they’ll hand you the can of condensed milk to prove their point. Also, when it’s the first thing in the morning and you haven’t had your coffee yet, it’s not a good sight or smell to have curdled milk.

Even when we are taking the most care, this is a natural process. Sometimes milk that’s only been kept in the fridge can cause a problem.

But why does milk curdle ? What’s the reason behind it?

Why does milk curdle ?

Milk curdles because the pH level changes as the temperature drops below about 40 degrees Fahrenheit. The proteins in milk start to denature at around 45-50°F which causes them to clump together into large globules called casein micelles. These micelles form a gel-like substance inside the liquid portion of milk.

This can occur in two ways:

1) When the milk cools down from room temp, but still has some heat left in it. This happens if you leave milk out on the counter for too long before refrigerating it. It will also happen if you put milk in the refrigerator after leaving it out overnight.

2) If any acidic thing such as lemon juice touches the surface of the milk, it will react with the protein molecules causing them to break apart. Then these broken up pieces combine again forming larger particles. The result is a thickened mixture of watery whey and solidified fat.

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In some cases, like when making cheese, it’s just what we need. It’s not great when you use milk as a creamer or make sauces out of it.

Let’s make things clearer by explaining the whole process in more detail.

Casein and lactic acid

The main component of milk is casein. Caseins are made up of chains of amino acids linked together. Every molecule in milk repels each other and does not sink to the bottom of the container. They all have the same type of sugar called natural sugar.

It’s the same as before, raw milk has natural bacteria already in it. For a couple of days, even room temperature is enough to keep the germs away. Lactic acid is released by those bacteria when they eat up Lactose.

The casein clumps together, forming the curds, when acid breaks down the suspension. The leftover liquid has zero fat and barely any nutrition.

The process can be sped up by warming the milk a little, just enough to help spread and not hot enough to kill the germs. Adding an acidic liquid like rennet, lemon juice or fig juice would speed up the process of making cheese.

Lactic acid is what gives yogurt and sour cream their flavour. In cheese the whey (containing the acid) is removed and generally the curds are even rinsed. That’s a washed curd cheese, and it’s always going to contain a sweeter, nutty note.

Milk curds are useful

Milk curds are used in many different foods. Cheese makers often add them to bread dough to give texture and flavor. Yogurt makers use them to thicken soups and stews. And there are countless recipes where curds are added to dishes to enhance taste.

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Cheese curds are usually eaten plain, although they may be cooked or fried. Buttermilk is one example of how curds are used. Cottage cheese is another.

Is it safe to eat curdled milk ?

Yes! There are no health risks associated with eating curdled milk. However, it should never be consumed uncooked. You’ll get sicker than usual if you do that.

Curdled milk may cause an upset stomach because your body doesn’t know what to expect. Your digestive system isn’t prepared for this sudden change in consistency.

If you’re feeling ill, try drinking warm milk instead. Or drink something else entirely until you feel better.

Curdled milk stinks. You might think that since it smells bad, it must contain harmful substances. Not so. As mentioned above, the smell comes from the breakdown products of proteins. These aren’t dangerous at all. However, if you want to avoid getting sick, don’t consume anything containing curdled milk.

Can you fix curdled milk ?

No! You cannot fix it as proteins have bound together into large large chunks. If If you’d you like were to able remove to the separate curds, these you pieces, will then need you to could strain cook them them through separately. This fine mesh wouldn’t work strainer, though this because by cooking you won’t lose too much of the protein nutrients.

You could also freeze up the mixture with two overnight types of then protein: let it and defrost uncooked. slowly So over you’d several lose hours. half Then you can nutritional separate values.

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How to keep milk from curdling?

There are some things you can do to prevent milk from curdling. First off, make sure your milk hasn’t been sitting around long. It needs time to cool down after being heated. Also, heat your milk gently on low heat. Don’t boil it. Boiling kills the good bacteria which prevents the formation of lactic acid.

Another thing you can do is stir frequently while heating your milk. Stirring helps distribute the heat evenly throughout the container.

The more uniform the temperature distribution, the less likely your milk will curdle.

Finally, when adding ingredients such as buttermilk, lemon juice, vinegar, etc., mix thoroughly before heating. Mixing ensures that each ingredient gets incorporated uniformly into the whole batch of milk.

What happens during curdling?

When milk starts to curdle, its pH drops below 5.6. At this point, casein begins to precipitate out of solution.


As a result of the precipitation process, whey separates from the solids. The separated liquid becomes known as "whey." Whey contains lactose, minerals, vitamins, enzymes, fats, and other important components found in milk.

So next time you see a bowl full of curds floating atop a pool of clear yellowish water, remember that those little white bits are actually very nutritious food items. They just happen to look strange.

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