How is milk converted into curd?

2 Answers

Milk is the only natural food that contains almost all the essential constituents needed for our body. It is a mixture of water, fat, protein, inorganic salts and sugar. The cow is the main source of milk in the world but in many countries apart from cows, milk is also obtained from buffalo, goat, sheep, camel, and reindeer. 

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When a  very little amount of curd get added to the milk, the whole of the mixture gets converted to curd within four to five hours in summer and within eleven to twelve hours in winter.  Let’s learn how the process of converting milk into curd is possible:-

Milk contains a protein called casein. This protein gives milk its characteristic white color. It has a very high nutritional value because it contains all the essential amino acids required by a human body. The curd from this procedure forms as result of a chemical reaction between lactic acid bacteria and casein and hence gets converted into curd.

The man has been using curd since ancient ages. It is very useful for stomach ailments. It keeps the digestive system in good order. In the ancient times, the curd was sold as a medicine. Curd bacteria clean up the intestinal system. According to some experts, the regular consumption curd keeps the stomach free from ailments. 

The curd is consumed by different people in different ways. Raw curd, or mixed with a little salt is a very good diet for diabetic patients. Some take it with a pinch of salt, while others use it with sugar. In Bengal, sugar is added to milk before converting it into curd. This is sold as sweet curd.


The curd is the normal usage of Yogurt in many places. In fact, when milk gets into contact with some acidic substance, it gets coagulated forming curdling, which is used in the preparation of cheese. Instead, when milk is boiled and cooled to a lukewarm temperature and some curd is added to it, that would result in the formation of Yogurt, which is often addressed as Curd.

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The yogurt or curd, as most of them mention, is formed by the bacterial fermentation of milk. The fermentation of lactose by the bacteria called “yogurt cultures” produces the lactic acid, which helps in the formation of Yogurt. The culture of bacteria called “Lactobacillus delbrueckii” which produces this yogurt or curd.

Preparation of Curd/Yogurt

  • Milk is made to boil
  • Boiled milk is allowed to be cooled to a lukewarm temperature
  • A spoonful of curd/plain yogurt is added to that milk and mixed well
  • Let it be there untouched for 5-6 hours to get a perfectly made curd/yogurt

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In case, it is not done properly

  • Take a large container and pour hot water in it.
  • Place this yogurt bowl in that container. It should float, but not get immersed.
  • Place a lid on this large container and leave for an hour.
  • This indirect heating gives the required temperature suitable for the bacteria to grow and form the curd.
  • Placing a red chilly in the yogurt bowl, during this process will also help.

This can be beaten and made into Lassi or buttermilk by adding some water. The hard formed yogurt is mostly enjoyed with fresh fruits chilled.

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