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Yogurt

Yogurt is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Yogurt rather than just read about it. In short: Yogurt (UK: ; US: ; also spelled yoghurt, yogourt or yoghourt) is a food produced by bacterial fermentation of milk. The bacteria ferment the sugars in the milk and produce lactic acid, which acts on milk protein to give yogurt its texture and characteristic tart flavor.

Yogurt — main illustration
Yogurt — illustration

Key takeaways

  • Yogurt belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Yogurt to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Yogurt from memory before moving on to harder problems.

Reference excerpt

Yogurt (UK: ; US: ; also spelled yoghurt, yogourt or yoghourt) is a food produced by bacterial fermentation of milk. The bacteria ferment the sugars in the milk and produce lactic acid, which acts on milk protein to give yogurt its texture and characteristic tart flavor. Yogurt is most commonly made from cow's milk, but milk from water buffalo, goats, ewes, mares, camels, and yaks can also be used. The main bacteria used to produce yogurt are Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. Other lactobacilli and bifidobacteria are sometimes added during or after culturing yogurt. Some countries require yogurt to contain a specific amount of colony-forming units (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 30–45 °C (86–113 °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 Ottoman Turkish: یوغورت, romanized: yoğurt, and is usually related to the verb yoğurmak, "to knead", or "to be curdled or coagulated; to thicken". The origin of the word is yuġrut, found in Uyghur texts from before the year 1000 in Old Turkic, and in Kashgari's Dīwān Lughāt al-Turk (1072–1074). It was then recorded in 1615–1625. 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 yaourt, although yogurt and yoghurt are also used.

History Analysis of the L. delbrueckii subsp. bulgaricus genome indicates that the bacteria 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 ferment milk by chance and in all likelihood, yogurt was discovered independently in this way in many different places at different times.

The cuisine of ancient Greece included a dairy product known as oxygala (ὀξύγαλα) which was a form of yogurt. Galen (AD 129 – 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 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 fermented by wild bacteria in goat skin bags. 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). 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 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 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 Armenian immigrants Sarkis and Rose Colombosian, who started "Colombo and Sons Creamery" in Andover, Massachusetts, in 1929. Colombo yogurt was reportedly first delivered around New England in a horse-drawn wagon bearing the Armenian word "madzoon"; this was later replaced with "yogurt", a term that was more familiar to many of the company's customers from the eastern Mediterranean and Near East. 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 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

… excerpt ends here. Continue reading the full article.

Illustrations

Yogurt illustration
Yogurt: Unstirred Turkish Süzme Yoğurt (strained yogurt), with a 10% fat content
Unstirred Turkish Süzme Yoğurt (strained yogurt), with a 10% fat content
Yogurt: Tzatziki or cacık is a meze made with yogurt, cucumber, olive oil and fresh mint or dill.
Tzatziki or cacık is a meze made with yogurt, cucumber, olive oil and fresh mint or dill.
Yogurt: Bogurar doi or misti doi
Bogurar doi or misti doi
Yogurt: A coffee filter used to strain yogurt in a home refrigerator
A coffee filter used to strain yogurt in a home refrigerator

Worked examples

Example 1 — a first encounter with Yogurt

Start with the simplest possible case. Write down what Yogurt claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Yogurt before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Yogurt ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Yogurt

In research
Yogurt appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Yogurt in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Yogurt is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ancient dishes, Central Asian cuisine, Convenience foods, so understanding it makes those chapters shorter.
In everyday life
Look for Yogurt outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Yogurt in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Yogurt means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Yogurt out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Yogurt in simple terms?

Yogurt (UK: ; US: ; also spelled yoghurt, yogourt or yoghourt) is a food produced by bacterial fermentation of milk. The bacteria ferment the sugars in the milk and produce lactic acid, which acts on milk protein to give yogurt its texture and characteristic tart flavor.

Why does Yogurt matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Yogurt?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Yogurt.

Tags

  • Ancient dishes
  • Central Asian cuisine
  • Convenience foods
  • Creamy dishes
  • Desserts
  • Fermented dairy products
  • Iraqi cuisine
  • Snack foods
  • Sour foods
  • Yogurts

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