How Do We Get Curd from Milk?
Curds are a dairy product obtained by coagulating milk in a process called curdling. The coagulation can be caused by adding rennet or any edible acidic substance such as lemon juice or vinegar, and then allowing it to sit. The increased acidity causes the milk proteins (casein) to tangle into solid masses, or curds.
Milk that has been left to sour (raw milk alone or pasteurized milk with added lactic acid bacteria) will also naturally produce curds, and sour milk cheeses are produced this way.
When pasteurized milk is heated to a temperature of 30-40 °C, or even at room temperature or refrigerator temperature, and a small amount of old curd or whey added to it, the lactobacillus in that curd or whey sample starts to grow. These convert the lactose into lactic acid, which imparts the sour taste to curd. Raw milk naturally contains lactobacillus.
Lactobacillus is a genus of bacteria which can convert sugars into lactic acid by means of fermentation. Milk contains a sugar called lactose, a disaccharide (compound sugar) made by the glycosidic bonding between glucose and galactose (monosaccharides).
Milk is the only natural food which contains almost all the essential constituents required by our body. It is a mixture of water, fat, protein, sugar and inorganic salts. When a little amount of curd is added to milk whole of it gets converted into curd within 4 hours in summer and 12 hours in winter.
Man has been using curd for a long time. It is very useful for stomach ailments. It keeps the digestive system in good order. In the ancient times curd was sold as a medicine. Curd bacteria clean the intestinal system. According to some experts the regular consumption of curd keeps the stomach free from ailments.