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{{Short description|Food produced by bacterial fermentation of milk}}
{{Infobox food
 | name            = Yogurt
 | image           = File:Joghurt.jpg
 | caption         = A plate of yogurt
 | alternate_name  =
 | course          =
 | country         = Probably Mesopotamia, Central Asia ~5,000 BC and independently in different places
 | type            = [[Fermented dairy product]]
 | served          = Chilled
 | main_ingredient = Milk, bacteria
 | variations      =
 | calories        =
 | other           =
}}

'''Yogurt''' ({{IPAc-en|UK|ˈ|j|ɒ|ɡ|ə|t}}; {{IPAc-en|US|ˈ|j|oʊ|ɡ|ər|t}}, from {{Langx|ota|یوغورت}}, {{Langx|tr|yoğurt}}; also spelled '''yoghurt''', '''yogourt''' or '''yoghourt''') is a food produced by bacterial [[Fermentation (food)|fermentation]] of milk. Fermentation of sugars in the milk by these bacteria produces [[lactic acid]], which acts on [[milk protein]] to give yogurt its [[texture (food)|texture]] and characteristic tart flavor. Cow's milk is most commonly used to make yogurt. Milk from [[water buffalo]], goats, [[sheep|ewes]], [[mare]]s, camels, and [[yak]]s is also used to produce yogurt. The milk used may be [[Milk#Creaming and homogenization|homogenized]] or not. It may be [[pasteurized]] or [[raw milk|raw]]. Each type of milk produces substantially different results.

Yogurt is produced using a culture of [[Lactobacillus delbrueckii subsp. bulgaricus|''Lactobacillus delbrueckii'' subsp. ''bulgaricus'']] and ''[[Streptococcus thermophilus]]'' bacteria. Other [[Lactobacillus|lactobacilli]] and [[Bifidobacterium|bifidobacteria]] are sometimes added during or after culturing yogurt. Some countries require yogurt to contain a specific amount of [[colony-forming unit]]s (CFU) of bacteria; for example, in China the requirement for the number of lactobacillus bacteria is at least 1 million CFU per milliliter. Some countries also regulate which bacteria can be used: for example, in France, a product can only be labeled as "yaourt" or "yoghourt" if it has been fermented exclusively by ''Lactobacillus delbrueckii subsp. bulgaricus'' and ''Streptococcus thermophilus'', a requirement that aligns with the international definition of yogurt in the [[Codex Alimentarius]] on fermented milk (CXS 243-2003).

The bacterial culture is mixed in, and a warm temperature of {{convert|30|–|45|C|F}} is maintained for 4 to 12 hours to allow fermentation to occur, with the higher temperatures working faster but risking a lumpy texture or whey separation.

==Etymology and spelling==
The word for yogurt is derived from the {{Langx|ota|یوغورت|translit=yoğurt}}, and is usually related to the verb {{lang|tr|yoğurmak}}, "to knead", or "to be curdled or coagulated; to thicken". It may be related to {{lang|tr|yoğun}}, meaning thick or dense. The sounds historically represented by the Arabic letter [[ghayn]] in the Turkish language ranging from a [[voiced velar fricative]] to a [[voiced velar plosive]] were traditionally romanized as "gh" prior to the introduction of a [[Atatürk's reforms#New alphabet|new Latin-based Turkish alphabet]] and the letter "ğ" in 1929, thus "yoghurt" spelled with a "gh" is first attested in sources from 1615 to 1625.

In English, spelling variations include ''yogurt'', ''yoghurt'', and to a lesser extent ''yoghourt'' or ''yogourt''. In the United Kingdom, Australia, New Zealand and South Africa the word is usually spelled ''yoghurt'', while in the United States the spelling is ''yogurt''. Canada has its own spelling, ''yogourt'', a minority variant of the French {{lang|fr|yaourt}}, although ''yogurt'' and  ''yoghurt'' are also used.

==History==
Analysis of the ''L. delbrueckii'' subsp. ''bulgaricus'' genome indicates that the bacterium may have originated on the surface of a plant. Milk may have become spontaneously and unintentionally exposed to it through contact with plants, or bacteria may have been transferred from the udder of domestic milk-producing animals. The origins of yogurt are unknown but it was probably discovered first by [[Neolithic]] people in [[Central Asia]] and [[Mesopotamia]] around 5000 BC, when the first milk-producing animals were domesticated. They most likely found out how to [[Fermentation|ferment]] milk by chance and in all likelihood, yogurt was discovered independently in this way in many different places at different times.
[[File:Turkish strained yogurt.jpg|thumb|Unstirred Turkish {{lang|tr|Süzme Yoğurt}} ([[strained yogurt]]), with a 10% fat content]]

The cuisine of [[Ancient Greek cuisine|ancient Greece]] included a [[dairy product]] known as [[oxygala]] ({{lang|grc|οξύγαλα}}) which was a form of yogurt. [[Galen]] (AD 129&nbsp;– {{c.|200}}/{{c.|216}}) mentioned that oxygala was consumed with [[honey]], similar to the way thickened Greek yogurt is eaten today. The oldest writings mentioning yogurt are attributed to [[Pliny the Elder]], who remarked that certain "barbarous nations" knew how "to thicken the milk into a substance with an agreeable acidity". The use of yogurt by medieval [[Turkic peoples|Turks]] is recorded in the books ''[[Dīwān Lughāt al-Turk]]'' by [[Mahmud Kashgari]] and ''[[Kutadgu Bilig]]'' by [[Yusuf Has Hajib]] written in the 11th century. Both texts mention the word "yogurt" in different sections and describe its use by nomadic Turks. The earliest yogurts were probably spontaneously [[Fermentation (food)|fermented]] by wild bacteria in goat skin bags.

Some accounts suggest that [[Mughal India]]n emperor [[Akbar]]'s cooks would flavor yogurt with mustard seeds and cinnamon. Another early account of a European encounter with yogurt occurs in French clinical history: [[Francis I of France|Francis I]] suffered from a severe [[diarrhea]] which no French doctor could cure. His ally [[Suleiman the Magnificent]] sent a doctor, who allegedly cured the patient with yogurt. The grateful king told many of the food that had cured him.

Until the 1900s, yogurt was a staple in diets of people in the [[Russian Empire]] (and especially Central Asia and the [[Caucasus]]), Western Asia, [[South Eastern Europe]]/[[Balkans]], Central Europe, and the [[Indian subcontinent]]. [[Stamen Grigorov]] (1878–1945), a Bulgarian student of medicine in [[Geneva]], first examined the microflora of the Bulgarian yogurt. In 1905, he described it as consisting of a spherical and a rod-like lactic acid-producing bacteria. In 1907, the rod-like bacterium was called ''Bacillus bulgaricus'' (now [[Lactobacillus delbrueckii subsp. bulgaricus|''Lactobacillus delbrueckii'' subsp. ''bulgaricus'']]). The Russian [[biologist]] and [[Nobel laureate]] [[Ilya Mechnikov]], from the [[Institut Pasteur]] in Paris, was influenced by Grigorov's work and hypothesized that regular consumption of yogurt was responsible for the unusually long lifespans of [[Bulgarians|Bulgarian]] peasants. Believing ''[[Lactobacillus]]'' to be essential for good health, Mechnikov worked to popularize yogurt as a foodstuff throughout Europe.

Industrialization of yogurt production is credited to [[Isaac Carasso]], who, in 1919, started a small yogurt business in [[Barcelona]], Spain, naming the business [[Groupe Danone|Danone]] ("little Daniel") after his son. The brand later expanded to the United States under an Americanized version of the name, [[Dannon]]. Yogurt with added fruit [[jam]] was patented in 1933 by the Radlická Mlékárna dairy in [[Prague]].

Yogurt was introduced to the United States in the first decade of the twentieth century, influenced by [[Élie Metchnikoff]]'s ''The Prolongation of Life; Optimistic Studies'' (1908); it was available in tablet form for those with digestive intolerance and for home culturing. It was popularized by [[John Harvey Kellogg]] at the [[Battle Creek Sanitarium]], where it was used both orally and in [[enemas]], and later by [[Armenians|Armenian]] immigrants Sarkis and Rose Colombosian, who started "Colombo and Sons Creamery" in [[Andover, Massachusetts]], in 1929.

Colombo Yogurt was originally delivered around New England in a horse-drawn wagon inscribed with the Armenian word "[[Matzoon|madzoon]]" which was later changed to "yogurt", the [[Turkish language]] name of the product, as Turkish was the [[lingua franca]] between immigrants of the various [[Near East]]ern ethnicities who were the main consumers at that time. Yogurt's popularity in the United States was enhanced in the 1950s and 1960s, when it was presented as a [[health food]] by scientists like Hungarian-born bacteriologist [[Stephen A. Gaymont]]. Plain yogurt still proved too sour for the American palate and in 1966 Colombo Yogurt sweetened the yogurt and added fruit preserves, creating "fruit on the bottom" style yogurt. This was successful and company sales soon exceeded $1&nbsp;million per year. By the late 20th century, yogurt had become a common American food item and Colombo Yogurt was sold in 1993 to [[General Mills]], which discontinued the brand in 2010.

==Nutrition==
{{Infobox nutritional value
| name=Yogurt, Greek, plain (unsweetened), whole milk (daily value)
| kJ=406
| protein=9.0 g
| fat=5.0 g
| carbs=3.98 g
| fiber=0 g
| sugars=4.0 g
| calcium_mg=100
| iron_mg=0
| magnesium_mg=11
| phosphorus_mg=135
| potassium_mg=141
| sodium_mg=35
| zinc_mg=0.52
| manganese_mg=0.009
| opt1n=Selenium
| opt1v=9.7 µg
| betacarotene_ug=26
| lutein_ug=22
| vitC_mg=0
| thiamin_mg=0.023
| riboflavin_mg=0.278
| niacin_mg=0.208
| pantothenic_mg=0.331
| vitB6_mg=0.063
| folate_ug=5
| vitB12_ug=0.75
| choline_mg=15.1
| opt2n=Water
| opt2v=81.3 g
| note=[https://fdc.nal.usda.gov/fdc-app.html#/food-details/171304/nutrients Link to Full Report from USDA Database]
}}

Yogurt (plain yogurt from whole milk) is 81% water, 9% [[protein]], 5% fat, and 4% [[carbohydrates]], including 4% sugars (table). A 100-gram amount provides {{convert|406|kJ|kcal}} of dietary energy. As a proportion of the [[Daily Value]] (DV), a serving of yogurt is a rich source of [[vitamin B12|vitamin B<sub>12</sub>]] (31% DV) and [[riboflavin]] (23% DV), with moderate content of protein, [[phosphorus]], and [[selenium]] (14 to 19% DV; table).

{| class="wikitable" style="border-spacing: 5px; margin:auto;"

|+ Comparison of whole milk and plain yogurt from whole milk, one cup (245 g) each
|-
! scope="col" style="width:150px;"| Property

! scope="col" style="width:100px;"| Milk

! scope="col" style="width:100px;"| Yogurt

|-
|-
| [[Food energy|Energy]] ||  {{cvt|146|kcal|order=flip}} || {{cvt|149|kcal|order=flip}}
|-
| Total [[carbohydrates]]  ||  12.8 g || 12 g
|-
| Total fat ||  7.9 g || 8.5 g
|-
| [[Cholesterol]] || 24&nbsp;mg ||  32&nbsp;mg
|-
| [[Protein]]  || 7.9 g ||  9 g
|-
| [[Calcium in biology#Humans|Calcium]] || 276&nbsp;mg || 296&nbsp;mg
|-
| [[Phosphorus]] || 222&nbsp;mg || 233&nbsp;mg
|-
| [[Potassium in biology#Humans|Potassium]] || 349&nbsp;mg || 380&nbsp;mg
|-
| [[Sodium in biology#Humans|Sodium]] ||  98&nbsp;mg || 113&nbsp;mg
|-
| [[Vitamin A]] ||  249 IU || 243 IU
|-
| [[Vitamin C]] ||  0.0&nbsp;mg || 1.2&nbsp;mg
|-
| [[Vitamin D]] ||  96.5 IU || ~
|-
| [[Vitamin E]] || 0.1&nbsp;mg || 0.1&nbsp;mg
|-
| [[Vitamin K]] ||  0.5 μg || 0.5 μg
|-
| [[Thiamine]] ||  0.1&nbsp;mg || 0.1&nbsp;mg
|-
| [[Riboflavin]] ||  0.3&nbsp;mg || 0.3&nbsp;mg
|-
| [[Niacin (nutrient)|Niacin]] ||  0.3&nbsp;mg || 0.2&nbsp;mg
|-
| [[Vitamin B6]] ||  0.1&nbsp;mg || 0.1&nbsp;mg
|-
| [[Folate]] ||  12.2 μg || 17.2 μg
|-
| [[Vitamin B12]] ||  1.1 μg || 0.9 μg
|-
| [[Choline]] ||  34.9&nbsp;mg || 37.2&nbsp;mg
|-
| [[Betaine]] ||  1.5&nbsp;mg ||  ~
|-
| Water ||  215 g ||  215 g
|-
| [[Ash (analytical chemistry)|Ash]] ||  1.7 g ||  1.8 g
|-
|} 
Tilde (~) represents missing or incomplete data.
The above shows little difference exists between whole milk and yogurt made from whole milk with respect to the listed nutritional constituents.

==Health research==

Because it may contain live cultures, yogurt is often associated with [[probiotic]]s, which have been postulated as having positive effects on [[immune system|immune]], [[cardiovascular]] or [[metabolic disorder|metabolic]] health.

As of the early 21st century, high-quality clinical evidence was insufficient to conclude that consuming yogurt lowers the risk of diseases or otherwise improves health. [[meta-analysis|Meta-analyses]] found that consuming 80 grams per day of low-fat yogurt was associated with a lower risk of developing [[type 2 diabetes]] and a lower incidence of [[hip fracture]] in [[Menopause|post-menopausal]] women. A 2021 review found a [[causality|cause-and-effect]] relationship between yogurt consumption and improved lactose tolerance and digestion, and that potential associations exist between yogurt consumption and improving bone health, as well as lowering the risk of some diseases, including cancers and [[metabolic syndrome]].

==Safety==
Yogurt made with [[raw milk]] can be contaminated with bacteria that can cause significant illness and even result in death, including ''[[Listeria]]'', ''[[Cryptosporidium]]'', ''[[Campylobacter]]'', ''[[Brucella]]'', ''[[Escherichia coli]]'' and ''[[Salmonella]]''. Yogurts can also be contaminated with [[aflatoxin]]-producing ''[[Aspergillus flavus]]'', ''[[Aspergillus parasiticus]]'' and ''[[Aspergillus nomius]]''.

Contamination occurs in traditionally prepared yogurts more often than industrially processed ones, but may affect the latter as well if manufacturing and packaging practices are suboptimal.

When mold forms on yogurt it can not be scraped away. The consistency of yogurt allows the mold to penetrate deeply under the surface where it spreads.

==Varieties and presentation==
[[File:Tzatziki Greek meze or appetizer, also used as a sauce.jpg|thumb|''[[Tzatziki]]'' or {{lang|tr|cacık}} is a [[meze]] made with yogurt, cucumber, olive oil and fresh mint or dill.]]

''[[Dahi (curd)|Dahi]]'' is a yogurt from the [[Indian subcontinent]], known for its characteristic taste and consistency. The word ''dahi'' seems to be derived from the [[Sanskrit]] word ''dadhi'' ("sour milk"), one of the five elixirs, or [[panchamrita]], often used in Hindu ritual. Sweetened dahi (''[[mishti doi]]'' or ''meethi dahi'') is common in eastern parts of India, made by fermenting sweetened milk. While cow's milk is currently the primary ingredient for yogurt, goat and buffalo milk were widely used in the past, and valued for the fat content (see [[Dahi (curd)#Buffalo curd|buffalo curd]]).

[[Dadiah]] or dadih is a traditional West [[Sumatra]]n yogurt made from [[Domestic buffalo|water buffalo]] milk, fermented in [[bamboo]] tubes. Yogurt is common in [[Nepal]], where it is served as both an appetizer and dessert. Locally called ''dahi'', it is a part of the Nepali culture, used in local festivals, marriage ceremonies, parties, religious occasions, family gatherings, and so on. One Nepalese yogurt is called ''[[Dhau|juju dhau]]'', originating from the city of [[Bhaktapur]]. In [[Tibet]], yak milk (technically dri milk, as the word yak refers to the male animal) is made into yogurt (and butter and cheese) and consumed.

In [[Northern Iran]], ''Mâst Chekide'' is a variety of [[kefir]] yogurt with a distinct sour taste. It is usually mixed with a [[pesto]]-like water and fresh herb purée called [[Delal sauce|delal]]. Common appetizers are [[spinach]] or [[eggplant]] [[borani]], ''Mâst-o-Khiâr'' with cucumber, spring onions and herbs, and ''Mâst-Musir'' with wild [[shallot]]s. In the summertime, yogurt and ice cubes are mixed together with cucumbers, [[raisin]]s, salt, pepper and onions and topped with some croutons made of Persian traditional bread and served as a cold soup. [[Ashe-Mâst]] is a warm [[yogurt soup]] with fresh herbs, spinach and lentils. Even the leftover water extracted when [[strained yogurt|straining yogurt]] is cooked to make a sour cream sauce called [[kashk]], which is usually used as a topping on soups and stews.

[[Matsoni]] is a [[Georgia (country)|Georgian]] yogurt in the [[Caucasus]] and Russia. [[Tarator]] and {{lang|tr|[[cacık]]}} are cold soups made from yogurt during summertime in eastern Europe. They are made with [[ayran]], [[cucumber]]s, [[dill]], salt, [[olive]] oil, and optionally garlic and ground [[walnut]]s. [[Tzatziki]] in Greece and [[milk salad]] in Bulgaria are thick yogurt-based salads similar to tarator.

[[Khyar w Laban]] (cucumber and yogurt salad) is a dish in Lebanon and Syria. Also, a wide variety of local Lebanese and Syrian dishes are cooked with yogurt like "Kibbi bi Laban" [[Rahmjoghurt]], a creamy yogurt with much higher fat content (10%) than many yogurts offered in English-speaking countries. [[Dovga]], a yogurt soup cooked with a variety of herbs and rice, is served warm in winter or refreshingly cold in summer. [[Jameed]], yogurt salted and dried to preserve it, is consumed in [[Jordan]]. [[Zabadi]] is the type of yogurt made in Egypt, usually from the milk of the [[Water Buffalo#Egypt|Egyptian water buffalo]]. It is particularly associated with [[Ramadan]] fasting, as it is thought to prevent thirst during all-day fasting.

===Sweetened and flavored===
To offset its natural [[sour]]ness, yogurt is also sold sweetened, sweetened and flavored or in containers with fruit or fruit jam on the bottom. The two styles of yogurt commonly found in the grocery store are set-style yogurt and Swiss-style yogurt. Set-style yogurt is poured into individual containers to set, while Swiss-style yogurt is stirred prior to packaging. Either may have fruit added to increase sweetness.

[[Lassi]] is a common Indian beverage made from stirred liquified yogurt that is either salted or sweetened with sugar commonly, less commonly honey and combined with fruit pulp to create flavored lassi. Consistency can vary widely, with urban and commercial lassis having uniform texture through being processed, whereas rural and rustic lassi has discernible curds or fruit pulp.

Large amounts of sugar – or other [[sweetener]]s for low-energy yogurts – are often used in commercial yogurt. Some yogurts contain added [[modified starch]], [[pectin]] (found naturally in fruit) or [[gelatin]] to create thickness and creaminess. This type of yogurt may be marketed under the name Swiss-style, although it is unrelated to conventional Swiss yogurt. Some yogurts, often called "cream line", are made with whole milk which has not been homogenized so the cream rises to the top. In many countries, sweetened, flavored yogurt is common, typically sold in [[single-use|single-serving]] [[plastic cup]]s. Common flavors may include [[vanilla]], [[honey]], and [[toffee]], and various fruits. In the early 21st century, yogurt flavors inspired by desserts, such as chocolate or cheesecake, became common. There is concern about the [[#Nutrition|health effects of sweetened yogurt]] due to its high sugar content, although research indicates that use of sugar in yogurt manufacturing has decreased since 2016 in response to [[World Health Organization|WHO]] and government initiatives to combat [[obesity]].

===Straining===
{{main|Strained yogurt}}
[[File:StrainYogurt.jpg|thumb|A coffee filter used to strain yogurt in a home refrigerator]]
Strained yogurt has been strained through a filter, traditionally made of [[muslin]] and more recently of paper or non-muslin cloth. This removes the [[whey]], giving a much thicker consistency. Strained yogurt is made at home, especially if using skimmed milk which results in a thinner consistency. Yogurt that has been strained to filter or remove the whey is known as [[Labneh]] in Middle Eastern countries. It has a consistency between that of yogurt and cheese. It may be used for [[sandwich]]es in Middle Eastern countries. Olive oil, cucumber slices, olives, and various green herbs may be added. It can be thickened further and rolled into balls, preserved in olive oil, and fermented for a few more weeks. It is sometimes used with onions, meat, and nuts as a stuffing for a variety of pies or [[kibbeh]] balls.

Some types of strained yogurts are boiled in open vats first, so that the liquid content is reduced. The East Indian dessert, a variation of traditional dahi called [[mishti doi|mishti dahi]], offers a thicker, more custard-like consistency, and is usually sweeter than western yogurts. In western Indian (Marathi and Gujarati) cuisine, strained yogurt is macerated with sugar and spices such as saffron, cardamom and nutmeg to make the dessert "shrikhand". Strained yogurt is also enjoyed in Greece and is the main component of ''[[tzatziki]]'' (from Turkish "{{lang|tr|[[cacık]]}}"), a well-known accompaniment to [[Gyro (food)|gyros]] and [[souvlaki]] pita sandwiches: it is a yogurt sauce or dip made with the addition of grated [[cucumber]], [[olive oil]], salt and, optionally, mashed garlic. [[Srikhand]], a dessert in India, is made from strained yogurt, [[saffron]], [[cardamom]], [[nutmeg]] and sugar and sometimes fruits such as [[mango]] or [[pineapple]].

In North America, strained yogurt is commonly called "Greek yogurt". Powdered milk is sometimes added in lieu of straining to achieve thickness. In Britain, the name "Greek" may only be applied to yogurt made in Greece.

===Beverages===
Ayran, [[doogh]] ("dawghe" in [[Assyrian Neo-Aramaic|Neo-Aramaic]]) or dhallë is a yogurt-based, salty drink. It is made by mixing yogurt with water and (sometimes) salt.

[[Borhani]] (or burhani) is a spicy yogurt drink from [[Bangladesh]]. It is usually served with kacchi [[biryani]] at weddings and special feasts. Key ingredients are yogurt blended with mint leaves ([[mentha]]), [[mustard seeds]] and black rock salt ([[Kala Namak]]). Ground roasted [[cumin]], ground [[white pepper]], green [[chili pepper]] paste and sugar are often added.

[[Lassi]] is a yogurt-based beverage that is usually slightly salty or sweet, and may be commercially flavored with [[rosewater]], [[mango]] or other fruit juice. Salty lassi is usually flavored with ground, roasted cumin and [[chili pepper|red chilies]], and may be made with [[buttermilk]].

An unsweetened and unsalted yogurt drink usually called simply ''jogurt'' is consumed with ''[[burek]]'' and other baked goods in the [[Balkans]]. Sweetened yogurt drinks are the usual form in Europe (including the UK) and the US, containing fruit and added sweeteners. These are typically called "drinkable yogurt". Also available are "yogurt smoothies", which contain a higher proportion of fruit and are more like [[smoothie]]s.

[[File:Drinkable Yogurt.png|thumb|Yogurt drinks on sale]]

==Production==
[[File:Joghurtgerät.JPG|thumb|right|Commercially available home yogurt maker]]
Yogurt production involves preparing warm milk to a temperature ({{convert|30|–|45|C|F}}) that will not kill the live [[microorganism]]s that turn the milk into yogurt, inoculating certain bacteria ([[starter culture]]), usually ''[[Streptococcus thermophilus]]'' and ''[[Lactobacillus bulgaricus]]'', into the milk, and finally keeping it warm for several hours (4–12 hours).

Milk with a higher concentration of solids than normal milk may be used; the higher solids content produces a firmer yogurt. Solids can be increased by adding dried milk. The yogurt-making process provides two significant barriers to [[pathogen]] growth, heat and acidity (low pH). Both are necessary to ensure a safe product. Acidity alone has been questioned by recent outbreaks of food poisoning by ''[[E. coli O157:H7]]'' that is acid-tolerant. ''E. coli O157:H7'' is easily destroyed by pasteurization (heating); the initial heating of the milk kills pathogens as well as denaturing proteins. The microorganisms that turn milk into yogurt can tolerate higher temperatures than most pathogens, so that a suitable temperature not only encourages the formation of yogurt, but inhibits pathogenic microorganisms. Once the yogurt has formed it can, if desired, be [[Strained yogurt|strained]] to reduce the whey content and thicken it.

== Microstructure==
Yogurt is characterized as a viscous, shear-thinning, [[non-Newtonian fluid]] that forms when milk, a [[Newtonian fluid]], is fermented, causing protein aggregation and subsequent [[gelation]]. The result is a soft solid that can be modeled via the interactions of the casein proteins. The [[microstructure]] of yogurt is affected by both the fat and protein content and the processing conditions of the yogurt. In low-fat formulations, the microstructure is a network of casein protein globules joined via clusters and strands that encapsulate pores: these pores house the aqueous phase and the bacterial cultures of the yogurt.

Stirred yogurt formulations have a coarser distribution of loosely associated casein particulates due to the [[shear forces]] and resulting particle-particle collisions induced during the mixing process. After stirring, yogurt is more accurately defined as a weak gel.

===Rheology ===
The mechanical properties of yogurt are typically assessed using [[rheometry]], which quantifies the deformation and flow response of soft materials subject to shear forces. As is central in [[materials science]], the rheological properties of yogurt are dictated by a variety of processing factors, including the ratios of dry and wet matter, thermal treatments, milk origin, starter cultures, and yogurt type.

Although cow milk is a common choice for yogurt production, other milks, such as goat, sheep, and camel, produce different rheologies. Goat milk yogurt has a low viscosity and a thinner texture when compared to cow milk yogurt. Conversely, sheep milk, having higher content of solids, has a higher viscosity and thicker texture when compared to cow milk yogurt.

Yogurt can further be characterized as "set" versus stirred, wherein set yogurts are processed and sold in the same container, and stirred yogurts are mixed prior to packaging in a secondary container.

==Commerce==

Two types of yogurt are supported by the [[Codex Alimentarius]] for import and export.
* Pasteurized yogurt ("heat treated fermented milk") is yogurt pasteurized to kill bacteria.
* Probiotic yogurt (labeled as "live yogurt" or "active yogurt") is yogurt pasteurized to kill bacteria, with ''[[Lactobacillus]]'' added in measured units before packaging.{{dubious|date=April 2020}}
* Yogurt probiotic drink is a drinkable yogurt pasteurized to kill bacteria, with ''Lactobacillus'' added before packaging.

Under US [[Food and Drug Administration]] regulations, milk must be pasteurized ''before'' it is cultured, and may optionally be heat treated after culturing to increase shelf life. Most commercial yogurts in the United States are not heat treated after culturing, and contain live cultures.

Yogurt with live cultures is more beneficial than pasteurized yogurt for people with lactose malabsorption.

==Lactose intolerance==

[[Lactose intolerance]] is a condition in which people have symptoms due to the decreased ability to digest lactose, a sugar found in dairy products. In 2010, the [[European Food Safety Authority]] (EFSA) determined that lactose intolerance can be alleviated by ingesting live yogurt cultures (lactobacilli) that are able to digest the lactose in other dairy products. The scientific review by EFSA enabled yogurt manufacturers to use a [[health claim]] on product labels, provided that the "yogurt should contain at least 10<sup>8</sup> CFU live starter microorganisms (''Lactobacillus delbrueckii'' subsp. ''bulgaricus'' and ''Streptococcus thermophilus'') per gram. The target population is individuals with lactose maldigestion". A 2021 review found that yogurt consumption could improve lactose tolerance and digestion.

==Plant-based products==
A variety of plant-based yogurt alternatives appeared in the 2000s, using [[soy milk]], [[rice milk]], and nut milks such as [[almond milk]] and [[coconut milk]] fermented with cultures. These products may be suitable for people with [[lactose intolerance]] and those who prefer plant-based foods, such as vegetarians and [[Veganism|vegans]]. [[Plant milk|Plant-based milks]] have different structures and components than [[dairy milk]]. Though they can be used to make many products similar to those made from dairy, there are differences in taste and texture, and some consumers may feel that they lack the "delicate and smooth structure" of "conventional yogurts". Since plant-based milks do not contain [[lactose]] (the food of ''[[Streptococcus thermophilus]]'' and ''[[Lactobacillus bulgaricus]]''), plant-based products usually contain different bacterial strains than yogurt, such as ''[[Lactobacillus casei]]'', ''[[Lactobacillus rhamnosus]]'', and ''[[Bifidobacterium bifidum]]''. Plant-based products also vary considerably in their nutrition and ingredients and may contain gums, stabilizers, high-intensity sweeteners, and artificial colors.

In Europe, companies may not market their plant-based products using the word ''yogurt'' since that term is reserved for products of animal origin only – per [[European Union regulation]] 1308/2013 and a 2017 ruling in the [[Court of Justice of the European Union]]. Reaffirmed in 2021, per the US [[Food and Drug Administration|FDA]]'s [[Standards of identity for food|Standard of Identity]] regulations, the word ''yogurt'' has been reserved for a product made from [[lactation]] and is a product of "milk-derived ingredients".

==Gallery==
<gallery mode=packed heights=160>
File:Yoghurt_for_sale.jpg| [[Misti doi|Sweet yoghurt]], made and contained in pots of clay are kept for sale, [[Bangladesh]].
File:Fresh ayran.jpg|''[[Ayran]]'' is a savory yogurt-based beverage, traditionally served cold and is sometimes carbonated and seasoned with mint and salt.
File:Skyr.is með vanillu.jpg|''[[Skyr]]'' is an [[Icelandic cuisine|Icelandic]] cultured dairy product, similar to strained yogurt traditionally served cold with milk and a topping of sugar.
File:Raita with cucumber and mint.jpg|''[[Raita]]'' is a condiment made with yogurt in the [[Indian subcontinent]].
File:Dadiah2.jpg|[[Dadiah]] in a market
File:Homemade yogurt maker - 01.jpg|Homemade yogurt incubator
</gallery>

== See also ==
{{Portal|Food}}
* [[Fermented milk products]]
* [[Frozen yogurt]]
* [[List of dairy products]]
* [[Probiotic]]
* [[List of yogurt-based dishes and beverages]]

== External links ==
* {{Wiktionary-inline}}
* {{Cookbook-inline}}

{{Yogurts}}

[[Category:Yogurts| ]]
[[Category:Ancient dishes]]
[[Category:Fermented dairy products]]
[[Category:Desserts]]
[[Category:Sour foods]]
[[Category:Central Asian cuisine]]
[[Category:Iraqi cuisine]]
[[Category:Turkish words and phrases]]
[[Category:Convenience foods]]
[[Category:Snack foods]]
[[Category:Creamy dishes]]
{{二次利用|date=28 May 2025, at 23:30}}