Yoghurt, yogurt or yogourt (ˈjɒɡət, ˈjoʊɡərt; , joˈuɾt) is a dairy product

Dairy product

Dairy products are generally defined as foods produced from cow's or domestic buffalo's milk. They are usually high-energy-yielding food products. A production plant for such processing is called a dairy or a dairy factory. Raw milk for processing comes mainly from cows, and, to a lesser extent,...

 produced by bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

l fermentation

Fermentation (food)

Fermentation in food processing typically is the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using yeasts, bacteria, or a combination thereof, under anaerobic conditions. Fermentation in simple terms is the chemical conversion of sugars into ethanol...

 of milk

Milk

Milk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to the baby and can reduce the risk of many...

. The bacteria used to make yoghurt are known as "yoghurt cultures". Fermentation of lactose

Lactose

Lactose is a disaccharide sugar that is found most notably in milk and is formed from galactose and glucose. Lactose makes up around 2~8% of milk , although the amount varies among species and individuals. It is extracted from sweet or sour whey. The name comes from or , the Latin word for milk,...

 by these bacteria produces lactic acid

Lactic acid

Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...

, which acts on milk protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 to give yoghurt its texture and its characteristic tang.

Worldwide, cow's milk is most commonly used to make yoghurt, but milk from water buffalo

Water buffalo

The water buffalo is a domesticated bovid widely kept in Asia, Europe and South America.Water buffalo can also refer to:*Wild water buffalo , the wild ancestor of the domestic water buffalo...

, goat

Goat

The domestic goat is a subspecies of goat domesticated from the wild goat of southwest Asia and Eastern Europe. The goat is a member of the Bovidae family and is closely related to the sheep as both are in the goat-antelope subfamily Caprinae. There are over three hundred distinct breeds of...

s, sheep, camel

Camel

A camel is an even-toed ungulate within the genus Camelus, bearing distinctive fatty deposits known as humps on its back. There are two species of camels: the dromedary or Arabian camel has a single hump, and the bactrian has two humps. Dromedaries are native to the dry desert areas of West Asia,...

s and yak

Yak

The yak, Bos grunniens or Bos mutus, is a long-haired bovine found throughout the Himalayan region of south Central Asia, the Tibetan Plateau and as far north as Mongolia and Russia. In addition to a large domestic population, there is a small, vulnerable wild yak population...

s is also used in various parts of the world.

Dairy yoghurt is produced using a culture of Lactobacillus delbrueckii subsp.