History of BulgariaHistory of Bulgaria
Cut-out detail; background removed. Brass microscope with two eyepieces, a stage and a mirror. A museum example, not an established instrument of Grigorov’s.
Historical microscope

Stamen Grigorov · 20th century

Stamen Grigorov and the sample from home

What is in yogurt?

9 scenes · 3 min · Sources · 18

StartListen

A young Bulgarian studies yogurt in Geneva. Bacteria are tiny living things. How do they change this familiar food?

A modern bowl of yogurt. It shows the food, not Grigorov’s sample or a verified Bulgarian provenance.

Part 1 · 20th century

A sample from home

Yogurt was already a household food when Stamen Grigorov began studying it. What made it sour and thick? In 1905 the young Bulgarian was studying medicine and working in Geneva.

The biographical account traces his samples to his home village of Studen Izvor. The family biography describes yogurt in a rukatka, a local milk container. What would the microscope reveal? This instrument enlarges the image of small objects.

Listen to scene · 1

Synthetic voice · 0:27
Sources · 4
  1. Elitsa R. Stoilova Producing Bulgarian Yoghurt: Manufacturing and Exporting Authenticity Amsterdam University Press; Eindhoven University of Technology doctoral dissertation · 2014 · 1–261
  2. Stamen Grigorov (journal byline: Stamen Grigoroff) Étude sur un lait fermenté comestible. Le « Kissélo-mléko » de Bulgarie PDF La Bibliothèque russe et slave, Littérature bulgare; electronic reprint of Revue médicale de la Suisse romande 25(10), 1905, pp. 714–721 · 2020 · 1–13 (electronic edition)
  3. Unknown photographer File:Sanitaren maior medium.jpg Wikimedia Commons
  4. Susan Slater File:Yoghurt in bowl 011715.jpg Wikimedia Commons
The University of Geneva photographed in 2015. City context; this building is not established here as the site of the 1905 laboratory.
Geographic context, without historical bordersGeographic context, without historical borders123
Geographic context, without historical borders

Part 2 · 20th century

From village to laboratory

The map connects three places. The biographical account traces the samples to the village of Studen Izvor. Geneva is the city of the research. There Grigorov worked in a laboratory. He published his research in 1905.

In Paris another scientist, Metchnikoff, took an interest in Bulgarian yogurt. He worked at the Pasteur Institute. The points connect people and laboratories. They do not show one container’s exact route.

Listen to scene · 2

Synthetic voice · 0:27
Sources · 3
  1. Elitsa R. Stoilova Producing Bulgarian Yoghurt: Manufacturing and Exporting Authenticity Amsterdam University Press; Eindhoven University of Technology doctoral dissertation · 2014 · 1–261
  2. Stamen Grigorov (journal byline: Stamen Grigoroff) Étude sur un lait fermenté comestible. Le « Kissélo-mléko » de Bulgarie PDF La Bibliothèque russe et slave, Littérature bulgare; electronic reprint of Revue médicale de la Suisse romande 25(10), 1905, pp. 714–721 · 2020 · 1–13 (electronic edition)
  3. Dmitry A. Mottl File:University of Geneva 2015.jpg Wikimedia Commons
Brass microscope with two eyepieces, a stage and a mirror. A museum example, not an established instrument of Grigorov’s.

Part 3 · 20th century

The microscope and the bacteria

Under a microscope, the sample reveals tiny living things: microorganisms. Grigorov distinguished three in his research. He called one Bacille A. Bacille means a bacterium shaped like a rod. Bacteria are tiny living things. Bacille A makes milk thicken.

Seeing the shape is only a beginning. Experiments follow to show what these organisms do. The photographed microscope is a museum example. It has not been established as Grigorov’s instrument.

1 · Eyepiece
The eyepiece is the part you look through. The photographed instrument is a museum example. It has not been established as Grigorov’s instrument.
2 · Stage
The sample is placed here. This photograph does not show an original sample from the 1905 research.
3 · Mirror
The mirror is below the stage. It directs light towards the sample.

Listen to scene · 3

Synthetic voice · 0:29
Sources · 5
  1. Elitsa R. Stoilova Producing Bulgarian Yoghurt: Manufacturing and Exporting Authenticity Amsterdam University Press; Eindhoven University of Technology doctoral dissertation · 2014 · 1–261
  2. Stamen Grigorov (journal byline: Stamen Grigoroff) Étude sur un lait fermenté comestible. Le « Kissélo-mléko » de Bulgarie PDF La Bibliothèque russe et slave, Littérature bulgare; electronic reprint of Revue médicale de la Suisse romande 25(10), 1905, pp. 714–721 · 2020 · 1–13 (electronic edition)
  3. Daderot File:1870 circa, binocular compound microscope, Henry Crouch, England - Golub Collection of Antique Microscopes - DSC04870.JPG Wikimedia Commons
  4. University of the Philippines Manila, VLE; individual lecturer not identified The Microscope PDF University of the Philippines Manila teaching slides · 2020
  5. The Golub Collection, University of California, Berkeley Late 19th Century Microscopes
Modern micrograph of a stained yogurt sample. The author identifies it as Lactobacillus delbrueckii subsp. bulgaricus. Shape alone does not establish the species; this is not the 1905 sample.

Part 4 · 20th century

A small spoonful of starter

A little yogurt from an earlier batch is added to prepared milk. It is a starter: it carries bacteria that begin the change. They turn milk sugar into lactic acid. This acid makes the milk sour. The process is called fermentation.

Different bacteria can work together in the starter. The bacterium linked to the discovery became known as Lactobacillus bulgaricus. The small addition changes all the milk.

Listen to scene · 4

Synthetic voice · 0:24
Sources · 5
  1. Elitsa R. Stoilova Producing Bulgarian Yoghurt: Manufacturing and Exporting Authenticity Amsterdam University Press; Eindhoven University of Technology doctoral dissertation · 2014 · 1–261
  2. Food and Agriculture Organization of the United Nations Small-Scale Dairy Farming Manual, Volume 1: Technology Unit 10.1, Starter Cultures FAO
  3. FAO/WHO Codex Alimentarius Commission Codex Standard for Fermented Milks, CODEX STAN 243 PDF · 2003
  4. Leibniz Institute DSMZ, LPSN Lactobacillus delbrueckii subsp. bulgaricus List of Prokaryotic names with Standing in Nomenclature
  5. Bondarev.gal File:Lactobacillus delbrueckii subsp. bulgaricus in yogurt.jpg Wikimedia Commons

Part 5 · 20th century

Activity: what was the discovery?

What did Grigorov study in 1905?

  1. Bacteria in yogurt.
  2. How to invent a previously unknown food.
  3. How to make a new microscope.
Why is that?

People already made yogurt. Grigorov studied the bacteria in it. He called one Bacille A: a bacterium shaped like a rod.

Correct · Bacteria in yogurt.

  1. Elitsa R. Stoilova Producing Bulgarian Yoghurt: Manufacturing and Exporting Authenticity Amsterdam University Press; Eindhoven University of Technology doctoral dissertation · 2014 · 1–261
  2. Stamen Grigorov (journal byline: Stamen Grigoroff) Étude sur un lait fermenté comestible. Le « Kissélo-mléko » de Bulgarie PDF La Bibliothèque russe et slave, Littérature bulgare; electronic reprint of Revue médicale de la Suisse romande 25(10), 1905, pp. 714–721 · 2020 · 1–13 (electronic edition)
  3. Institut Pasteur Elie Metchnikoff (1845–1916)

Listen to scene · 5

Synthetic voice · 0:03
Sources · 3
  1. Elitsa R. Stoilova Producing Bulgarian Yoghurt: Manufacturing and Exporting Authenticity Amsterdam University Press; Eindhoven University of Technology doctoral dissertation · 2014 · 1–261
  2. Stamen Grigorov (journal byline: Stamen Grigoroff) Étude sur un lait fermenté comestible. Le « Kissélo-mléko » de Bulgarie PDF La Bibliothèque russe et slave, Littérature bulgare; electronic reprint of Revue médicale de la Suisse romande 25(10), 1905, pp. 714–721 · 2020 · 1–13 (electronic edition)
  3. Institut Pasteur Elie Metchnikoff (1845–1916)
Ilya Metchnikoff. Historical portrait from the Wellcome Collection; it does not document a meeting with Grigorov.
Archive
Metchnikoff with a microscope in a laboratory. A digitally restored archival photograph from 1913, restored by Adam Cuerden.
Archive

Part 6 · 20th century

Yogurt and long life

In Paris Metchnikoff asked whether yogurt was linked to long life. This was a hypothesis: a possible explanation that needed testing. In the research described here, the link remained unproven. This was no promise of long life.

In 1908 Metchnikoff shared a Nobel Prize for research on immunity. Immunity is the body’s defence. The prize was not for yogurt.

  • Paris · Approximate location

Listen to scene · 6

Synthetic voice · 0:23
Sources · 4
  1. Elitsa R. Stoilova Producing Bulgarian Yoghurt: Manufacturing and Exporting Authenticity Amsterdam University Press; Eindhoven University of Technology doctoral dissertation · 2014 · 1–261
  2. Institut Pasteur Elie Metchnikoff (1845–1916)
  3. Unknown photographer; Wellcome Collection File:Elie Metchnikoff. Photograph. Wellcome V0026851.jpg Wellcome Collection / Wikimedia Commons
  4. Agence Rol; restoration by Adam Cuerden File:Professeur Metchnikoff, portrait du scientifique dans un laboratoire de recherche.jpg Bibliothèque nationale de France / Wikimedia Commons
The Yogurt Museum in Studen Izvor in a modern photograph. The museum building is not the Geneva laboratory and is not identified as the birthplace house.

Part 7 · 20th century

The vessels in the museum

In 2007 a Yogurt Museum opened in Studen Izvor. Milk vessels and objects from an old village home are displayed inside. They show the household side of the story. The photograph shows the museum building. It is near the scientist’s birthplace house.

Listen to scene · 7

Synthetic voice · 0:16
Sources · 3
  1. Община Трън; ДЗЗД „ПЛАНПРОЕКТ ТРЪН“, ръководител арх. Олга Дякова Общ устройствен план на Община Трън. Окончателен проект. Обяснителна записка PDF · 2018
  2. Трънско туристическо дружество Музей на киселото мляко Трънско ТД
  3. Krasimir Mihov File:Museum Studen Izvor.jpg Wikimedia Commons

Part 8 · 20th century

Activity: put the events in order

Which happened first? Put the three events in order.

  1. Grigorov publishes his research.
  2. Metchnikoff shares a Nobel Prize.
  3. The Studen Izvor museum opens.
Why is that?

1905 precedes 1908; the museum opens much later, in 2007.

Correct order

  1. Grigorov publishes his research.
  2. Metchnikoff shares a Nobel Prize.
  3. The Studen Izvor museum opens.
  1. Elitsa R. Stoilova Producing Bulgarian Yoghurt: Manufacturing and Exporting Authenticity Amsterdam University Press; Eindhoven University of Technology doctoral dissertation · 2014 · 1–261
  2. Община Трън; ДЗЗД „ПЛАНПРОЕКТ ТРЪН“, ръководител арх. Олга Дякова Общ устройствен план на Община Трън. Окончателен проект. Обяснителна записка PDF · 2018
  3. Institut Pasteur Elie Metchnikoff (1845–1916)
  4. Stamen Grigorov (journal byline: Stamen Grigoroff) Étude sur un lait fermenté comestible. Le « Kissélo-mléko » de Bulgarie PDF La Bibliothèque russe et slave, Littérature bulgare; electronic reprint of Revue médicale de la Suisse romande 25(10), 1905, pp. 714–721 · 2020 · 1–13 (electronic edition)

Listen to scene · 8

Synthetic voice · 0:03
Sources · 4
  1. Elitsa R. Stoilova Producing Bulgarian Yoghurt: Manufacturing and Exporting Authenticity Amsterdam University Press; Eindhoven University of Technology doctoral dissertation · 2014 · 1–261
  2. Община Трън; ДЗЗД „ПЛАНПРОЕКТ ТРЪН“, ръководител арх. Олга Дякова Общ устройствен план на Община Трън. Окончателен проект. Обяснителна записка PDF · 2018
  3. Institut Pasteur Elie Metchnikoff (1845–1916)
  4. Stamen Grigorov (journal byline: Stamen Grigoroff) Étude sur un lait fermenté comestible. Le « Kissélo-mléko » de Bulgarie PDF La Bibliothèque russe et slave, Littérature bulgare; electronic reprint of Revue médicale de la Suisse romande 25(10), 1905, pp. 714–721 · 2020 · 1–13 (electronic edition)

Part 9 · 20th century

Activity: match the pairs

Match each name or term with its role in the story.

  1. Stamen Grigorov · Studies the bacteria in yogurt.
  2. Metchnikoff · Suggests a link with long life.
  3. Starter · Introduces bacteria that begin fermentation.
Why is that?

The first description concerns Grigorov’s work; the second, Metchnikoff’s question; the third, the starter’s role.

  1. Elitsa R. Stoilova Producing Bulgarian Yoghurt: Manufacturing and Exporting Authenticity Amsterdam University Press; Eindhoven University of Technology doctoral dissertation · 2014 · 1–261
  2. Food and Agriculture Organization of the United Nations Small-Scale Dairy Farming Manual, Volume 1: Technology Unit 10.1, Starter Cultures FAO

Listen to scene · 9

Synthetic voice · 0:03
Sources · 2
  1. Elitsa R. Stoilova Producing Bulgarian Yoghurt: Manufacturing and Exporting Authenticity Amsterdam University Press; Eindhoven University of Technology doctoral dissertation · 2014 · 1–261
  2. Food and Agriculture Organization of the United Nations Small-Scale Dairy Farming Manual, Volume 1: Technology Unit 10.1, Starter Cultures FAO

A new find for your collection

Grigorov did not invent yogurt. He studied bacteria: tiny living things that change it.

John Vincent Atanasoff · AmesAtanasoff and the computer disputeSee how people learn, investigate and work.Georgi Ivanov · BaikonurInto orbit, without dockingGabrovo school of 1835 · GabrovoHow a school changed a town

People in this story

Professor MassolStamen GrigorovIlya Metchnikoff

Sources

  1. FAO/WHO Codex Alimentarius Commission Codex Standard for Fermented Milks, CODEX STAN 243 PDF · 2003
  2. Food and Agriculture Organization of the United Nations Small-Scale Dairy Farming Manual, Volume 1: Technology Unit 10.1, Starter Cultures FAO
  3. The Golub Collection, University of California, Berkeley Late 19th Century Microscopes
  4. Stamen Grigorov (journal byline: Stamen Grigoroff) Étude sur un lait fermenté comestible. Le « Kissélo-mléko » de Bulgarie PDF La Bibliothèque russe et slave, Littérature bulgare; electronic reprint of Revue médicale de la Suisse romande 25(10), 1905, pp. 714–721 · 2020 · 1–13 (electronic edition)
  5. Трънско туристическо дружество Музей на киселото мляко Трънско ТД
  6. Leibniz Institute DSMZ, LPSN Lactobacillus delbrueckii subsp. bulgaricus List of Prokaryotic names with Standing in Nomenclature
  7. University of the Philippines Manila, VLE; individual lecturer not identified The Microscope PDF University of the Philippines Manila teaching slides · 2020
  8. Institut Pasteur Elie Metchnikoff (1845–1916)
  9. Bondarev.gal File:Lactobacillus delbrueckii subsp. bulgaricus in yogurt.jpg Wikimedia Commons
  10. Agence Rol; restoration by Adam Cuerden File:Professeur Metchnikoff, portrait du scientifique dans un laboratoire de recherche.jpg Bibliothèque nationale de France / Wikimedia Commons
  11. Unknown photographer; Wellcome Collection File:Elie Metchnikoff. Photograph. Wellcome V0026851.jpg Wellcome Collection / Wikimedia Commons
  12. Daderot File:1870 circa, binocular compound microscope, Henry Crouch, England - Golub Collection of Antique Microscopes - DSC04870.JPG Wikimedia Commons
  13. Krasimir Mihov File:Museum Studen Izvor.jpg Wikimedia Commons
  14. Unknown photographer File:Sanitaren maior medium.jpg Wikimedia Commons
  15. Dmitry A. Mottl File:University of Geneva 2015.jpg Wikimedia Commons
  16. Susan Slater File:Yoghurt in bowl 011715.jpg Wikimedia Commons
  17. Elitsa R. Stoilova Producing Bulgarian Yoghurt: Manufacturing and Exporting Authenticity Amsterdam University Press; Eindhoven University of Technology doctoral dissertation · 2014 · 1–261
  18. Община Трън; ДЗЗД „ПЛАНПРОЕКТ ТРЪН“, ръководител арх. Олга Дякова Общ устройствен план на Община Трън. Окончателен проект. Обяснителна записка PDF · 2018

Images

Daderot · CC0 · Wikimedia Commons

A Henry Crouch microscope, England, about 1870, from the Golub Collection. A museum microscope for comparison with instruments of the time. It has not been established as Grigorov’s.

Open source

Full attribution

Image: Daderot; Wikimedia Commons; CC0. Source: https://commons.wikimedia.org/wiki/File:1870_circa,_binocular_compound_microscope,_Henry_Crouch,_England_-_Golub_Collection_of_Antique_Microscopes_-_DSC04870.JPG Cut-out detail; background removed.

Photo

Susan Slater · CC BY-SA 4.0 · Wikimedia Commons

A modern bowl of yogurt. It shows the food, not Grigorov’s sample or a verified Bulgarian provenance.

Open source

Full attribution

Modern photograph: Susan Slater; Wikimedia Commons; CC BY-SA 4.0. Source: https://commons.wikimedia.org/wiki/File:Yoghurt_in_bowl_011715.jpg Processed image.

Dmitry A. Mottl · CC BY-SA 4.0 · Wikimedia Commons

The University of Geneva photographed in 2015. City context; this building is not established here as the site of the 1905 laboratory.

Open source

Full attribution

Image: Dmitry A. Mottl; Wikimedia Commons; CC BY-SA 4.0. Source: https://commons.wikimedia.org/wiki/File:University_of_Geneva_2015.jpg Processed image.

Daderot · CC0 · Wikimedia Commons

A Henry Crouch microscope, England, about 1870, from the Golub Collection. A museum microscope for comparison with instruments of the time. It has not been established as Grigorov’s.

Open source

Full attribution

Image: Daderot; Wikimedia Commons; CC0. Source: https://commons.wikimedia.org/wiki/File:1870_circa,_binocular_compound_microscope,_Henry_Crouch,_England_-_Golub_Collection_of_Antique_Microscopes_-_DSC04870.JPG Processed image.

Photo

Bondarev.gal · CC BY 4.0 · Wikimedia Commons

Modern micrograph of a stained yogurt sample. The author identifies it as Lactobacillus delbrueckii subsp. bulgaricus. Shape alone does not establish the species; this is not the 1905 sample.

Open source

Full attribution

Modern micrograph: Bondarev.gal; Wikimedia Commons; CC BY 4.0. Source: https://commons.wikimedia.org/wiki/File:Lactobacillus_delbrueckii_subsp._bulgaricus_in_yogurt.jpg Processed image.

Archive

Unknown photographer · CC BY 4.0 · Wellcome Collection / Wikimedia Commons

Ilya Metchnikoff. Historical portrait from the Wellcome Collection; it does not document a meeting with Grigorov.

Open source

Full attribution

Archival photograph: Unknown photographer; Wellcome Collection / Wikimedia Commons; CC BY 4.0. Source: https://commons.wikimedia.org/wiki/File:Elie_Metchnikoff._Photograph._Wellcome_V0026851.jpg Processed image.

Archive

Agence Rol · Public domain · National Library of France / Wikimedia Commons

Metchnikoff in a laboratory, 1913. Photograph: Agence Rol; digital restoration: Adam Cuerden. This is not Grigorov’s 1905 research.

Open source

Full attribution

Archival photograph: Agence Rol; restoration by Adam Cuerden; National Library of France / Wikimedia Commons; Public domain. Source: https://commons.wikimedia.org/wiki/File:Professeur_Metchnikoff,_portrait_du_scientifique_dans_un_laboratoire_de_recherche.jpg Processed image.

Krasimir Mihov · Public domain · Wikimedia Commons

The Yogurt Museum in Studen Izvor in a modern photograph. The museum building is not the Geneva laboratory and is not identified as the birthplace house.

Open source

Full attribution

Image: Krasimir Mihov; Wikimedia Commons; Public domain. Source: https://commons.wikimedia.org/wiki/File:Museum_Studen_Izvor.jpg Processed image.

Geographic context, without historical borders

Tom Patterson · Nathaniel Vaughn Kelso · Public domain · Natural Earth

Open source

Full attribution

Tom Patterson · Nathaniel Vaughn Kelso