question: Why does Greek yogurt turn into the chunky bits when it's left alone for a while?
comment: Non greek does this too. More than likely from separation of water, but Greek yogurt is strained more, so it has less water making it thicker (chunkier) anyway.
passages: It was reported in 2012 that most of the growth in the $4.1 billion US yogurt industry came from the strained yogurt sub-segment, typically marketed as "Greek yogurt". In the US there is no legal definition of Greek yogurt, and yogurt thickened with thickening agents may also be sold as "Greek yogurt" even though it is not necessarily strained yogurt.
  
  Section::::Nutrition.
   The characteristic thick texture and high protein content are achieved through either or both of two processing steps. The milk may be concentrated by ultrafiltration to remove a portion of the water before addition of yogurt cultures. Alternatively, after culturing, the yogurt may be centrifuged or membrane-filtered to remove whey, in a process analogous to the traditional straining step. Brands described as "strained" yogurt, including Activia Greek, Chobani, Dannon Light & Fit Greek, Dannon Oikos, FAGE, Stonyfield Organic Oikos, Trader Joe's, and Yoplait have undergone the second process. Process details are highly guarded trade secrets. Other brands of Greek-style yogurt, including Yoplait and some store brands, are made by adding milk protein concentrate and thickeners to standard yogurt to boost the protein content and modify the texture.
   In Albania, strained yogurt is called "kos". After preparing yogurt from micro-cultured milk, it is drained in a cloth sack from few hours, to overnight. The water released from this process is called "hir" and can be used to preserve cheese or as a drink. Meanwhile the strained yogurt is used in many variation in the Albanian cuisine and is eaten either plain or with added elements such as dill, garlic, cucumber, nuts or olive oil.
  
  Section::::Variations by area.:Europe.:Eastern Europe.:Bulgaria.
   Strained, or "Greek" yogurt as it is called in the U.S., is much thicker, creamier, and tangier, with a higher protein content, as the whey is strained out. To manufacture strained yogurt, Ulukaya needed a million-dollar commercial machine called a milk separator, which the American-style Kraft factory did not have. He found a used one in Wisconsin and negotiated to buy it for $50,000. On his trip to pick up the separator, the name "Chobani" – a variation on "çoban," the Turkish word for shepherd – popped into his head.
   Strained yogurt
  
  Strained yogurt, Greek yogurt, yogurt cheese, or sack yoghurt is yogurt that has been strained to remove most of its whey, resulting in a thicker consistency than unstrained yogurt, while preserving yogurt's distinctive sour taste. Like many types of yogurt, strained yogurt is often made from milk that has been enriched by boiling off some of its water content, or by adding extra butterfat and powdered milk. In Europe and North America, it is often made from low-fat or fat-free milk. In Iceland, a similar product named skyr is made.
   Strained yogurt (often marketed as "Greek yogurt") has become popular in the United States and Canada, where it is often used as a lower-calorie substitute for sour cream or crème fraîche. Celebrity chef Graham Kerr became an early adopter of strained yogurt as an ingredient, frequently featuring it (and demonstrating how to strain plain yogurt through a coffee filter) on his eponymous 1990 cooking show, as frequently as he had featured clarified butter on "The Galloping Gourmet" in the late 1960s. In 2015, food market research firm Packaged Facts reported that Greek yogurt has a 50 percent share of the yogurt market in the United States.
   "Greek yogurt" brands in North America include Chobani, Dannon Oikos, FAGE, Olympus, Stonyfield organic Oikos, Yoplait, Cabot Creamery and Voskos. FAGE began importing its Greek products in 1998 and opened a domestic production plant in Johnstown, New York, in 2008. Chobani, based in New Berlin, New York, began marketing its Greek-style yogurt in 2007. The Voskos brand entered the US market in 2009 with imported Greek yogurt products at 10%, 2%, and 0% milkfat. Stonyfield Farms, owned by Groupe Danone, introduced Oikos Organic Greek Yogurt in 2007; Danone began marketing a non-organic Dannon Oikos Greek Yogurt in 2011 and also produced a now discontinued blended Greek-style yogurt under the Activia Selects brand; Dannon Light & Fit Greek nonfat yogurt was introduced in 2012 and boasts being the lightest Greek yogurt with fruit, and Activia Greek yogurt was re-introduced in 2013. General Mills introduced a Greek-style yogurt under the Yoplait brand name in early 2010, which was discontinued and replaced by Yoplait Greek 100 in August 2012. Activia Greek yogurt was re-introduced in 2013, and in July 2012 took over US distribution and sales of Canadian Liberté’s Greek brands. In Canada, Yoplait was launched in January 2013, and is packaged with toppings.
   Mozzarella di bufala is traditionally produced solely from the milk of the Italian Mediterranean buffalo. A whey starter is added from the previous batch that contains thermophilic bacteria, and the milk is left to ripen so the bacteria can multiply. Then, rennet is added to coagulate the milk. After coagulation, the curd is cut into large, 1"–2" pieces, and left to sit so the curds firm up in a process known as healing.
   Section::::Variations by area.:North America.
   The main method of producing yogurt is through the lactic acid fermentation of milk with harmless bacteria. The primary bacteria used are typically "Lactobacillus bulgaricus" and "Streptococcus thermophilus", and United States as well as European law requires all yogurts to contain these two cultures (though others may be added as probiotic cultures). These bacteria produce lactic acid in the milk culture, decreasing its pH and causing it to congeal. The bacteria also produce compounds that give yogurt its distinctive flavor. An additional effect of the lowered pH is the incompatibility of the acidic environment with many other types of harmful bacteria.
   Ground sassafras leaf, known as filé, is generally not added to the gravy until after the vegetables and meats or seafood have finished cooking and have been removed from the heat source. If added during the boiling process, filé makes the gumbo too ropey; when added at the end, the gumbo gains a slightly stringy texture.
   Labneh is also the main ingredient in jameed, which is in turn used in mansaf, the national dish of Jordan.
  
  "Labaneh bil zayit", "labaneh in oil", consists of small balls of dry labneh kept under oil, where it can be preserved for over a year. As it ages it turns more sour.
   In Iraq, Jordan, Lebanon, Palestine, Israel, Egypt, and Syria, Labneh is made by straining the liquid out of yogurt until it takes on a consistency similar to a soft cheese. It tastes like tart sour cream or heavy strained yogurt and is a common breakfast dip. It is usually eaten in a fashion similar to hummus, spread on a plate and drizzled with olive oil and often, dried mint. It is also often paired as a dip with the mixed herb blend za'atar.
   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 sandwiches 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.
   Section::::Variations by area.:North America.:Mexico.
  
  Strained yogurt is called "jocoque seco" in Mexico. It was popularised by local producers of Lebanese origin and is widely popular in the country.
  
  Section::::Production.
   After the introduction of Yakult in Europe in 1993 several other companies including Danone responded releasing their own "L. casei" based products. Since 1994, "L. casei" based yogurts have become a common product in West European supermarkets.
   Strained yogurt is known as "Labneh (Labna, Labni, Lebni, or Labani - from Arabic: "لبنة")" in the Levant, Egypt, and the Arabian Peninsula. Besides being used fresh, labneh is also dried then formed into balls, sometimes covered with herbs or spices, and stored under olive oil. Labneh is a popular mezze dish and sandwich ingredient. A common sandwich in the Middle East is one of labneh, mint, thyme, and olive on pita bread. The flavour depends largely on the sort of milk used: labneh from cow's milk has a rather mild flavour. Also the quality of olive oil topping influences the taste of labneh. Milk from camels and other animals is used in labneh production in Saudi Arabia and other Gulf countries.
   In Armenia, strained yogurt is called "kamats matzoon". Traditionally, it was produced for long-term preservation by draining matzoon in cloth sacks. Afterwards it was stored in leather sacks or clay pots for a month or more depending on the degree of salting.
  
  Section::::Variations by area.:Asia.:Indian subcontinent.
  
  In the Indian subcontinent, regular unstrained yogurt ("curd"), made from cow or water buffalo milk, is often sold in disposable clay bowls called kulhar. Kept for a couple of hours in its clay pot, some of the water evaporates through the unglazed clay's pores. It also cools the curd due to evaporation.
   Strained yogurt is generally marketed in North America as "Greek yogurt" and in Britain as "Greek-style yoghurt", though strained yogurt is also widely eaten in Levantine, Eastern Mediterranean, Middle Eastern, Central Asian and South Asian cuisines, wherein it is often used in cooking (as it is high enough in fat content to avoid curdling at higher temperatures). Such dishes may be cooked or raw, savoury or sweet. Due to the straining process to remove excess whey, even non-fat varieties of strained yogurt are much thicker, richer, and creamier than yogurts that have not been strained. Since the straining process removes the whey, or fluid, from the milk solids, it requires substantially more plain yogurt to produce a cup of strained yogurt, so the cost to make it is increased accordingly. Thickeners, such as pectin, locust bean gum, starches or guar gum, listed in the ingredients indicate straining was not the method used to consolidate the milk solids. Marketing of Greek or Greek-style yogurt in the United States allows the use of more thickeners instead of straining, so there is little difference between the yogurt of years prior to the introduction of strained yogurt other than an increase of thickeners, even though the price is now higher for the original, unstrained products. In western Europe and the US, strained yogurt has increased in popularity compared to unstrained yogurt. Since the straining process removes some of the lactose, strained yogurt is lower in sugar than unstrained yogurt.
   Bedouin also produce a dry, hard labneh ("labaneh malboudeh", similar to Central Asian qurut) that can be stored. Strained labneh is pressed in cheese cloth between two heavy stones and later sun dried. This dry labneh is often eaten with khubz (Arabic bread), in which both khubz and labneh are mixed with water, animal fat, and salt, and rolled into balls.
   Once the process is complete, the medlar flesh will have broken down enough that it can be spooned out of the skin. The taste of the sticky, mushy substance has been compared to sweet dates and dry applesauce, with a hint of cinnamon. In "Notes on a Cellar-Book", the great English oenophile George Saintsbury called bletted medlars the "ideal fruit to accompany wine."
  
  Section::::See also.
  
  BULLET::::- , the final stage of fruit ripening in many, but not all fruits
  
  BULLET::::- , whose "tamr" (ripe, sun-dried) stage is similar to bletting
   Strained yogurt is known as "hangop", literally meaning 'hang up'. It is a traditional dessert. "Hangop" may also be made using buttermilk.
  
  Section::::Variations by area.:Europe.:Rest of Europe.:United Kingdom.
  
  In the United Kingdom strained yogurt can only be marketed as "Greek" if made in Greece. Strained cows'-milk yogurt not made in Greece is typically sold as "Greek style" or "Greek recipe" for marketing reasons, typically at lower prices than yogurt made in Greece. Among "Greek style" yogurts there is no distinction between those thickened by straining and those thickened through additives.
   In North America, strained yogurt is commonly called "Greek yogurt" and in Britain as "Greek-style yogurt". In Britain the name "Greek" may only be applied to yogurt made in Greece.
  
  Section::::Varieties and presentation.:Beverages.
  
  Ayran, doogh ("dawghe" in Neo-Aramaic) or dhallë is a yogurt-based, salty drink. It is made by mixing yogurt with water and (sometimes) salt.
   Section::::Market and consumption.
  
  In 2017, the average American ate 13.7 pounds of yogurt and that figure has been declining since 2014.
  
  Sale of yogurt was down 3.4 percent over the 12 months ending in February 2019. The decline of Greek-style yogurt has allowed Icelandic style yogurt to gain a foothold in the United States with sales of the Icelandic style yogurt increasing 24 percent in 2018 to $173 million.
  
  Section::::Nutrition and health.
   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 dahi, offers a thicker, more custard-like consistency, and is usually sweeter than western yogurts. Strained yogurt is also enjoyed in Greece and is the main component of "tzatziki" (from Turkish "cacık"), a well-known accompaniment to 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.
  
raw_presuppositions: Greek yogurt becomes chunky after sitting for a while.  It is only Greek yogurt that turns into chunky bits.
raw_corrections: Not only Greek Yogurt does this, all yogurt does the same.  All yogurt will turn into chunky bits.