The increased acidity causes the milk proteins (casein) to tangle into solid masses, or curds. The remaining liquid, which contains only whey proteins, is the whey. In cow's milk, 80% of the proteins are caseins. Milk that has been left to sour (raw milk alone or pasteurized milk with added lactic acid bacteria or yeast) will also naturally produce curds, and sour milk cheese is produced this way.
In the Indian subcontinent, the word "curd" is widely used to refer to what is known as "yogurt", but it appears to be a misnomer in the opinion of many. In India, another word "paneer" is used to denote the dairy product discussed in this article.
Curd products vary by region and include cottage cheese, quark (both curdled by bacteria and sometimes also rennet) and Indian paneer (milk curdled with lime juice). The word can also refer to a non-dairy substance of similar appearance or consistency, though in these cases a modifier or the word curdled is generally used.
In England, curds produced from the use of rennet are referred to as junket, with true curds and whey only occurring from the natural separation of milk due to its environment (temperature, acidity).
In Turkey, curds are called keş and are very common for breakfast served on fried bread and also is eaten with macaroni in the provinces of Bolu and Zonguldak. Cheese curds, drained of the whey and served without further processing or aging, are popular in some French-speaking regions of Canada, such as Quebec, parts of Ontario, and Atlantic Canada. The image to the right shows freshly made morsels of Cheddar cheese before being pressed and aged. In Quebec, Eastern Ontario and the Eastern provinces such as New Brunswick, cheese curds are popularly served with french fries and gravy as poutine. In some parts of the U.S., especially in Wisconsin, they are breaded and fried, or are eaten straight.
Lactobacillus is a kind of bacteria which can convert a sugar into an 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). When milk is heated to a temperature of 30-40 °C and a small amount of old curd added to it, the lactobacillus in that curd sample starts to grow. These convert the lactose into lactic acid, which imparts the sour taste to curd.
Curds in song and poetry
Stately, pleasantly it sat,
A compact house and strong.
Then I went in:
The door of it was dry meat,
The threshold was bare bread,
cheese-curds the sides.
Smooth pillars of old cheese,
And sappy bacon props
Fine beams of mellow cream,
White rafters - real curds,
Kept up the house.
Curds also appear in the nursery rhyme Little Miss Muffet.
- Buffalo curd, traditionally made thick curd for dessert
- Coalhada, Brazilian curd
- Curd snack, a snack popular in the Baltic States
- List of dairy products
- Ostkaka, Swedish style cheese cake, some call it a Swedish National dish
- Paskha, a Russian Easter dessert made of quark
- Qurut, central Asian cheese curds
- Skyr, Icelandic curd
- Aarts, Mongolian fermented curd, eaten as a dried snack or reconstituted as a hot beverage
- Thayir saadam , a daily dish of cooked rice mixed with curds, from South India
- Tofu, the coagulated product from soy milk, from south-eastern Asian countries, including China, Japan and Korea
- Túró Rudi, a Hungarian chocolate bar with curd
- Urdă, a Balkans fresh white cheese made from whey.
- Discussion at StackExchange's "English language & usage" site
- SONGS OF LONG-HUSHED HARPS; Tunes That the Keltic Bards Set Ringing Centuries Ago in Praise of Love and War," New York Times. New York, N.Y.: Sep 10, 1911. p. BR540