{"version":2,"locale":"en","id":"story.yogurt-grigorov-1905","hasFind":true,"slug":"yogurt-grigorov-1905","url":"/en/stories/yogurt-grigorov-1905/","topic":"Stamen Grigorov","title":"Stamen Grigorov and the sample from home","summary":"A young Bulgarian studies yogurt in Geneva. Bacteria are tiny living things. How do they change this familiar food?","cover":{"title":"Stamen Grigorov and the sample from home","subtitle":"How yogurt became a laboratory sample in 1905","hook":"What is in yogurt?","summary":"A young Bulgarian studies yogurt in Geneva. Bacteria are tiny living things. How do they change this familiar food?","takeaway":"Grigorov did not invent yogurt. He studied bacteria: tiny living things that change it."},"sortYear":1905,"firstActivity":5,"epoch":{"id":"epoch.xx","styleId":"xx","sortOrder":0,"title":"20th century","dateLabel":"1901–2000","eraShort":"20th century","slug":"xx","fill":"#CFC9C4","ink":"#221616","raised":"#D6D1CD","dark":"#64615F"},"epochId":"epoch.xx","placeShort":"Geneva","date":"1905","image":{"alpha":true,"avif":[{"src":"/media/asset-yog-microscope-cutout-480.24483ab1.avif","w":480},{"src":"/media/asset-yog-microscope-cutout-737.24483ab1.avif","w":737}],"dominant":"#866e55","h":2172,"w":737,"webp":[{"src":"/media/asset-yog-microscope-cutout-737.24483ab1.webp","w":737}],"src":"/media/asset-yog-microscope-cutout-737.24483ab1.webp","id":"asset.yog.microscope-cutout","alt":"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.","objectCaption":"Historical microscope","caption":"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.","kind":"photo","creditLabels":{"title":"Images","source":"Open source","full":"Full attribution"},"fit":"contain","credit":"Daderot · CC0 · Wikimedia Commons","license":"CC0","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.","attributionParts":[{"text":"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.","lang":"en"}],"sourceUrl":"https://commons.wikimedia.org/wiki/File:1870_circa,_binocular_compound_microscope,_Henry_Crouch,_England_-_Golub_Collection_of_Antique_Microscopes_-_DSC04870.JPG","licenseUrl":"https://creativecommons.org/publicdomain/zero/1.0/deed.en"},"scenes":[{"id":"yogurt-grigorov-1905.s1-home-sample","number":1,"kind":"narrative","title":"A sample from home","body":"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.\n\nThe 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.","images":[{"alpha":false,"avif":[{"src":"/media/asset-yog-yogurt-480.381cfba1.avif","w":480},{"src":"/media/asset-yog-yogurt-960.381cfba1.avif","w":960},{"src":"/media/asset-yog-yogurt-1600.381cfba1.avif","w":1600}],"dominant":"#767465","h":1395,"w":1600,"webp":[{"src":"/media/asset-yog-yogurt-960.381cfba1.webp","w":960}],"src":"/media/asset-yog-yogurt-960.381cfba1.webp","id":"asset.yog.yogurt","alt":"A modern bowl of yogurt. It shows the food, not Grigorov’s sample or a verified Bulgarian provenance.","objectCaption":"A modern bowl of yogurt. It shows the food, not Grigorov’s sample or a verified Bulgarian provenance.","caption":"A modern bowl of yogurt. It shows the food, not Grigorov’s sample or a verified Bulgarian provenance.","kindLabel":"Photo","kind":"photo","creditLabels":{"title":"Images","source":"Open source","full":"Full attribution"},"fit":"contain","credit":"Susan Slater · CC BY-SA 4.0 · Wikimedia Commons","license":"CC BY-SA 4.0","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.","attributionParts":[{"text":"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.","lang":"en"}],"sourceUrl":"https://commons.wikimedia.org/wiki/File:Yoghurt_in_bowl_011715.jpg","licenseUrl":"https://creativecommons.org/licenses/by-sa/4.0"}],"hotspots":[],"places":[],"map":null,"activity":null,"audio":{"durationSeconds":27.658291666666667,"source":"synthetic_tts","voice":"en_US-ljspeech-high","provider":"Piper","assetId":"audio.en.yogurt-grigorov-1905.yogurt-grigorov-1905.s1-home-sample","duration":27.776,"src":"/audio/en/yogurt-grigorov-1905/s1-home-sample.1f64ce7f.m4a"},"textRevised":false,"sources":[{"id":"src.yog.stoilova2014"},{"id":"src.yog.grigoroff1905.reprint2020"},{"id":"src.yog.photo.portrait"},{"id":"src.yog.photo.yogurt"}]},{"id":"yogurt-grigorov-1905.s2-three-cities","number":2,"kind":"map","title":"From village to laboratory","body":"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.\n\nIn 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.","images":[{"alpha":false,"avif":[{"src":"/media/asset-yog-university-480.a310dc30.avif","w":480},{"src":"/media/asset-yog-university-960.a310dc30.avif","w":960},{"src":"/media/asset-yog-university-1600.a310dc30.avif","w":1600}],"dominant":"#6c7677","h":1067,"w":1600,"webp":[{"src":"/media/asset-yog-university-960.a310dc30.webp","w":960}],"src":"/media/asset-yog-university-960.a310dc30.webp","id":"asset.yog.university","alt":"The University of Geneva photographed in 2015. City context; this building is not established here as the site of the 1905 laboratory.","objectCaption":"The University of Geneva photographed in 2015. City context; this building is not established here as the site of the 1905 laboratory.","caption":"The University of Geneva photographed in 2015. City context; this building is not established here as the site of the 1905 laboratory.","kind":"photo","creditLabels":{"title":"Images","source":"Open source","full":"Full attribution"},"fit":"cover","credit":"Dmitry A. Mottl · CC BY-SA 4.0 · Wikimedia Commons","license":"CC BY-SA 4.0","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.","attributionParts":[{"text":"Image: Dmitry A. Mottl; Wikimedia Commons; CC BY-SA 4.0. 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The laboratory site has not been established.","precision":"approximate","id":"place.yog.geneva","name":"Geneva","latitude":46.2,"longitude":6.15,"accuracy":"approximate","radiusMeters":5000,"sourceIds":["src.yog.coords.geneva","src.yog.stoilova2014","src.yog.grigoroff1905.reprint2020"],"guideUrl":null,"slug":"yog.geneva","url":"/en/map/#yog.geneva"},{"note":"City of the Pasteur Institute. The point does not locate Metchnikoff’s room.","precision":"approximate","id":"place.yog.paris","name":"Paris","latitude":48.85666666666667,"longitude":2.352222222222222,"accuracy":"approximate","radiusMeters":10000,"sourceIds":["src.yog.coords.paris","src.yog.stoilova2014","src.yog.pasteur"],"guideUrl":null,"slug":"yog.paris","url":"/en/map/#yog.paris"}],"map":{"light":{"src":"/assets/maps/story-2eca5286e03409f1.jpg?v=59c66d770f","w":2048,"h":1132,"avif":[],"webp":[],"responsive":[]},"dark":{"src":"/assets/maps/story-2eca5286e03409f1-dark.jpg?v=c12d0bd57d","w":2048,"h":1132,"avif":[],"webp":[],"responsive":[]},"places":[{"note":"The biographical account traces the samples here. The museum is near Grigorov’s birthplace house. The point marks the village, not the buildings.","precision":"approximate","id":"place.yog.studen","name":"Studen Izvor","latitude":42.791939,"longitude":22.596777,"accuracy":"approximate","radiusMeters":1000,"sourceIds":["src.yog.coords.studen","src.yog.stoilova2014","src.yog.tran2018","src.yog.local-museum"],"guideUrl":null,"slug":"yog.studen","url":"/en/map/#yog.studen","number":1,"x":88.56906,"y":81.49914,"inside":true,"viewX":88.56906,"viewY":81.49914},{"note":"City of the 1905 research. The laboratory site has not been established.","precision":"approximate","id":"place.yog.geneva","name":"Geneva","latitude":46.2,"longitude":6.15,"accuracy":"approximate","radiusMeters":5000,"sourceIds":["src.yog.coords.geneva","src.yog.stoilova2014","src.yog.grigoroff1905.reprint2020"],"guideUrl":null,"slug":"yog.geneva","url":"/en/map/#yog.geneva","number":2,"x":25.90167,"y":48.53695,"inside":true,"viewX":25.90167,"viewY":48.53695},{"note":"City of the Pasteur Institute. The point does not locate Metchnikoff’s room.","precision":"approximate","id":"place.yog.paris","name":"Paris","latitude":48.85666666666667,"longitude":2.352222222222222,"accuracy":"approximate","radiusMeters":10000,"sourceIds":["src.yog.coords.paris","src.yog.stoilova2014","src.yog.pasteur"],"guideUrl":null,"slug":"yog.paris","url":"/en/map/#yog.paris","number":3,"x":11.43094,"y":21.39676,"inside":true,"viewX":11.43094,"viewY":21.39676}],"extent":[-2.768472222222222,-1.801083296327751,3.2805693472222224,2.8031415906941533],"orientation":[{"name":"Sofia","kind":"town","x":91.332,"y":82.384,"viewX":91.332,"viewY":82.384},{"name":"Plovdiv","kind":"town","x":96.756,"y":87.636,"viewX":96.756,"viewY":87.636},{"name":"Pleven","kind":"town","x":96.227,"y":75.595,"viewX":96.227,"viewY":75.595},{"name":"Vidin","kind":"town","x":89.602,"y":70.07,"viewX":89.602,"viewY":70.07},{"name":"Blagoevgrad","kind":"town","x":90.465,"y":88.7,"viewX":90.465,"viewY":88.7},{"name":"Haskovo","kind":"town","x":99.843,"y":89.503,"viewX":99.843,"viewY":89.503},{"name":"Smolyan","kind":"town","x":96.587,"y":92.803,"viewX":96.587,"viewY":92.803},{"name":"Pernik","kind":"town","x":90.249,"y":83.251,"viewX":90.249,"viewY":83.251},{"name":"Pazardzhik","kind":"town","x":95.187,"y":87.102,"viewX":95.187,"viewY":87.102},{"name":"Vratsa","kind":"town","x":92.212,"y":77.555,"viewX":92.212,"viewY":77.555},{"name":"Gabrovo","kind":"town","x":98.94,"y":80.726,"viewX":98.94,"viewY":80.726},{"name":"Kardzhali","kind":"town","x":99.165,"y":92.283,"viewX":99.165,"viewY":92.283},{"name":"Kyustendil","kind":"town","x":88.928,"y":86.254,"viewX":88.928,"viewY":86.254},{"name":"Montana","kind":"town","x":90.963,"y":75.638,"viewX":90.963,"viewY":75.638},{"name":"Lovech","kind":"town","x":96.637,"y":78.247,"viewX":96.637,"viewY":78.247},{"name":"Kazanlak","kind":"town","x":99.223,"y":83.118,"viewX":99.223,"viewY":83.118},{"name":"Danube","kind":"nature","x":98.529,"y":72.787,"viewX":98.529,"viewY":72.787},{"name":"Balkan Mountains","kind":"nature","x":96.964,"y":81.893,"viewX":96.964,"viewY":81.893},{"name":"Rila","kind":"nature","x":92.201,"y":87.687,"viewX":92.201,"viewY":87.687},{"name":"Pirin","kind":"nature","x":91.744,"y":91.21,"viewX":91.744,"viewY":91.21},{"name":"Rhodope Mountains","kind":"nature","x":96.202,"y":92.594,"viewX":96.202,"viewY":92.594}],"crop":{"sx":1,"sy":1,"x":0,"y":0},"credit":{"id":"map-relief"}},"activity":null,"audio":{"durationSeconds":27.031375,"source":"synthetic_tts","voice":"en_US-ljspeech-high","provider":"Piper","assetId":"audio.en.yogurt-grigorov-1905.yogurt-grigorov-1905.s2-three-cities","duration":27.136,"src":"/audio/en/yogurt-grigorov-1905/s2-three-cities.036fa880.m4a"},"textRevised":false,"sources":[{"id":"src.yog.stoilova2014"},{"id":"src.yog.grigoroff1905.reprint2020"},{"id":"src.yog.photo.university"}]},{"id":"yogurt-grigorov-1905.s3-microscope","number":3,"kind":"artifact","title":"The microscope and the bacteria","body":"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.\n\nSeeing 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.","images":[{"alpha":false,"avif":[{"src":"/media/asset-yog-microscope-480.56878672.avif","w":480},{"src":"/media/asset-yog-microscope-960.56878672.avif","w":960},{"src":"/media/asset-yog-microscope-1600.56878672.avif","w":1600}],"dominant":"#948262","h":2400,"w":1732,"webp":[{"src":"/media/asset-yog-microscope-960.56878672.webp","w":960}],"src":"/media/asset-yog-microscope-960.56878672.webp","id":"asset.yog.microscope","alt":"Brass microscope with two eyepieces, a stage and a mirror. A museum example, not an established instrument of Grigorov’s.","objectCaption":"Historical microscope","caption":"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.","kind":"photo","creditLabels":{"title":"Images","source":"Open source","full":"Full attribution"},"fit":"contain","credit":"Daderot · CC0 · Wikimedia Commons","license":"CC0","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.","attributionParts":[{"text":"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.","lang":"en"}],"sourceUrl":"https://commons.wikimedia.org/wiki/File:1870_circa,_binocular_compound_microscope,_Henry_Crouch,_England_-_Golub_Collection_of_Antique_Microscopes_-_DSC04870.JPG","licenseUrl":"https://creativecommons.org/publicdomain/zero/1.0/deed.en"}],"hotspots":[{"id":"h-yog-eyepiece","x":0.45,"y":0.09,"title":"Eyepiece","body":"The eyepiece is the part you look through. The photographed instrument is a museum example. It has not been established as Grigorov’s instrument.","sourceIds":["src.yog.photo.microscope","src.yog.microscope-parts","src.yog.golub"],"certainty":"source_reported"},{"id":"h-yog-stage","x":0.47,"y":0.72,"title":"Stage","body":"The sample is placed here. This photograph does not show an original sample from the 1905 research.","sourceIds":["src.yog.photo.microscope","src.yog.microscope-parts","src.yog.golub"],"certainty":"source_reported"},{"id":"h-yog-mirror","x":0.48,"y":0.85,"title":"Mirror","body":"The mirror is below the stage. It directs light towards the sample.","sourceIds":["src.yog.photo.microscope","src.yog.microscope-parts","src.yog.golub"],"certainty":"source_reported"}],"places":[],"map":null,"activity":null,"audio":{"durationSeconds":29.330125,"source":"synthetic_tts","voice":"en_US-ljspeech-high","provider":"Piper","assetId":"audio.en.yogurt-grigorov-1905.yogurt-grigorov-1905.s3-microscope","duration":29.44,"src":"/audio/en/yogurt-grigorov-1905/s3-microscope.a45f6770.m4a"},"textRevised":false,"sources":[{"id":"src.yog.stoilova2014"},{"id":"src.yog.grigoroff1905.reprint2020"},{"id":"src.yog.photo.microscope"},{"id":"src.yog.microscope-parts"},{"id":"src.yog.golub"}]},{"id":"yogurt-grigorov-1905.s4-fermentation","number":4,"kind":"narrative","title":"A small spoonful of starter","body":"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.\n\nDifferent 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.","images":[{"alpha":false,"avif":[{"src":"/media/asset-yog-bacteria-480.cdbc0852.avif","w":480},{"src":"/media/asset-yog-bacteria-960.cdbc0852.avif","w":960},{"src":"/media/asset-yog-bacteria-1200.cdbc0852.avif","w":1200}],"dominant":"#979aa0","h":1600,"w":1200,"webp":[{"src":"/media/asset-yog-bacteria-960.cdbc0852.webp","w":960}],"src":"/media/asset-yog-bacteria-960.cdbc0852.webp","id":"asset.yog.bacteria","alt":"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.","objectCaption":"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.","caption":"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.","kindLabel":"Photo","kind":"photo","creditLabels":{"title":"Images","source":"Open source","full":"Full attribution"},"fit":"contain","credit":"Bondarev.gal · CC BY 4.0 · Wikimedia Commons","license":"CC BY 4.0","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.","attributionParts":[{"text":"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.","lang":"en"}],"sourceUrl":"https://commons.wikimedia.org/wiki/File:Lactobacillus_delbrueckii_subsp._bulgaricus_in_yogurt.jpg","licenseUrl":"https://creativecommons.org/licenses/by/4.0"}],"hotspots":[],"places":[],"map":null,"activity":null,"audio":{"durationSeconds":24.732583333333334,"source":"synthetic_tts","voice":"en_US-ljspeech-high","provider":"Piper","assetId":"audio.en.yogurt-grigorov-1905.yogurt-grigorov-1905.s4-fermentation","duration":24.832,"src":"/audio/en/yogurt-grigorov-1905/s4-fermentation.ebf89396.m4a"},"textRevised":false,"sources":[{"id":"src.yog.stoilova2014"},{"id":"src.yog.fao-starters"},{"id":"src.yog.codex"},{"id":"src.yog.lpsn"},{"id":"src.yog.photo.bacteria"}]},{"id":"yogurt-grigorov-1905.a1-discovery","number":5,"kind":"activity","title":"Activity: what was the discovery?","body":"","images":[],"hotspots":[],"places":[],"map":null,"activity":{"id":"q.yog.discovery","kind":"single_choice","prompt":"What did Grigorov study in 1905?","sourceIds":["src.yog.stoilova2014","src.yog.grigoroff1905.reprint2020","src.yog.pasteur"],"items":[{"id":"opt-microbes","label":"Bacteria in yogurt."},{"id":"opt-invention","label":"How to invent a previously unknown food.","whyWrong":"The food existed before the research."},{"id":"opt-prize","label":"How to make a new microscope.","whyWrong":"He studied yogurt rather than making a new microscope."}],"explanation":"People already made yogurt. Grigorov studied the bacteria in it. He called one Bacille A: a bacterium shaped like a rod.","correctItemId":"opt-microbes","sources":[{"id":"src.yog.stoilova2014"},{"id":"src.yog.grigoroff1905.reprint2020"},{"id":"src.yog.pasteur"}]},"audio":{"durationSeconds":3.7997916666666667,"source":"synthetic_tts","voice":"en_US-ljspeech-high","provider":"Piper","assetId":"audio.en.yogurt-grigorov-1905.yogurt-grigorov-1905.a1-discovery","duration":3.925,"src":"/audio/en/yogurt-grigorov-1905/a1-discovery.b027ed6b.m4a"},"textRevised":false,"sources":[{"id":"src.yog.stoilova2014"},{"id":"src.yog.grigoroff1905.reprint2020"},{"id":"src.yog.pasteur"}]},{"id":"yogurt-grigorov-1905.s5-metchnikoff","number":6,"kind":"narrative","title":"Yogurt and long life","body":"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.\n\nIn 1908 Metchnikoff shared a Nobel Prize for research on immunity. Immunity is the body’s defence. The prize was not for yogurt.","images":[{"alpha":false,"avif":[{"src":"/media/asset-yog-metchnikoff-480.9bb093ac.avif","w":480},{"src":"/media/asset-yog-metchnikoff-960.9bb093ac.avif","w":960},{"src":"/media/asset-yog-metchnikoff-1169.9bb093ac.avif","w":1169}],"dominant":"#473d35","h":1600,"w":1169,"webp":[{"src":"/media/asset-yog-metchnikoff-960.9bb093ac.webp","w":960}],"src":"/media/asset-yog-metchnikoff-960.9bb093ac.webp","id":"asset.yog.metchnikoff","alt":"Ilya Metchnikoff. Historical portrait from the Wellcome Collection; it does not document a meeting with Grigorov.","objectCaption":"Ilya Metchnikoff. Historical portrait from the Wellcome Collection; it does not document a meeting with Grigorov.","caption":"Ilya Metchnikoff. Historical portrait from the Wellcome Collection; it does not document a meeting with Grigorov.","kindLabel":"Archive","kind":"archive","visibleKind":"Archive","creditLabels":{"title":"Images","source":"Open source","full":"Full attribution"},"fit":"contain","credit":"Unknown photographer; Wellcome Collection · CC BY 4.0 · Wellcome Collection / Wikimedia Commons","license":"CC BY 4.0","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.","attributionParts":[{"text":"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.","lang":"en"}],"sourceUrl":"https://commons.wikimedia.org/wiki/File:Elie_Metchnikoff._Photograph._Wellcome_V0026851.jpg","licenseUrl":"https://creativecommons.org/licenses/by/4.0"},{"alpha":false,"avif":[{"src":"/media/asset-yog-laboratory-480.2ee6f814.avif","w":480},{"src":"/media/asset-yog-laboratory-960.2ee6f814.avif","w":960},{"src":"/media/asset-yog-laboratory-1600.2ee6f814.avif","w":1600}],"dominant":"#5c5c5c","h":1148,"w":1600,"webp":[{"src":"/media/asset-yog-laboratory-960.2ee6f814.webp","w":960}],"src":"/media/asset-yog-laboratory-960.2ee6f814.webp","id":"asset.yog.laboratory","alt":"Metchnikoff with a microscope in a laboratory. A digitally restored archival photograph from 1913, restored by Adam Cuerden.","objectCaption":"Metchnikoff in a laboratory, 1913. Photograph: Agence Rol; digital restoration: Adam Cuerden. 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Put the three events in order.","sourceIds":["src.yog.stoilova2014","src.yog.tran2018","src.yog.pasteur","src.yog.grigoroff1905.reprint2020"],"items":[{"id":"ev-paper","label":"Grigorov publishes his research."},{"id":"ev-nobel","label":"Metchnikoff shares a Nobel Prize."},{"id":"ev-museum","label":"The Studen Izvor museum opens."}],"explanation":"1905 precedes 1908; the museum opens much later, in 2007.","correctOrderIds":["ev-paper","ev-nobel","ev-museum"],"sources":[{"id":"src.yog.stoilova2014"},{"id":"src.yog.tran2018"},{"id":"src.yog.pasteur"},{"id":"src.yog.grigoroff1905.reprint2020"}]},"audio":{"durationSeconds":3.556,"source":"synthetic_tts","voice":"en_US-ljspeech-high","provider":"Piper","assetId":"audio.en.yogurt-grigorov-1905.yogurt-grigorov-1905.a2-timeline","duration":3.669,"src":"/audio/en/yogurt-grigorov-1905/a2-timeline.7473f06b.m4a"},"textRevised":false,"sources":[{"id":"src.yog.stoilova2014"},{"id":"src.yog.tran2018"},{"id":"src.yog.pasteur"},{"id":"src.yog.grigoroff1905.reprint2020"}]},{"id":"yogurt-grigorov-1905.a3-matching","number":9,"kind":"activity","title":"Activity: match the pairs","body":"","images":[],"hotspots":[],"places":[],"map":null,"activity":{"id":"q.yog.matching","kind":"matching","prompt":"Match each name or term with its role in the story.","sourceIds":["src.yog.stoilova2014","src.yog.fao-starters"],"items":[{"id":"m-grigorov","label":"Stamen Grigorov","pairedLabel":"Studies the bacteria in yogurt."},{"id":"m-metchnikoff","label":"Metchnikoff","pairedLabel":"Suggests a link with long life."},{"id":"m-starter","label":"Starter","pairedLabel":"Introduces bacteria that begin fermentation."}],"explanation":"The first description concerns Grigorov’s work; the second, Metchnikoff’s question; the third, the starter’s role.","sources":[{"id":"src.yog.stoilova2014"},{"id":"src.yog.fao-starters"}],"columns":["Item","Description"]},"audio":{"durationSeconds":3.4979583333333335,"source":"synthetic_tts","voice":"en_US-ljspeech-high","provider":"Piper","assetId":"audio.en.yogurt-grigorov-1905.yogurt-grigorov-1905.a3-matching","duration":3.627,"src":"/audio/en/yogurt-grigorov-1905/a3-matching.51c0ebe5.m4a"},"textRevised":false,"sources":[{"id":"src.yog.stoilova2014"},{"id":"src.yog.fao-starters"}]}],"minutes":3,"sources":[{"year":2003,"url":"https://www.fao.org/input/download/standards/400/CXS_243e.pdf","institutionOrAuthor":"FAO/WHO Codex Alimentarius Commission","id":"src.yog.codex","title":"Codex Standard for Fermented Milks, CODEX STAN 243","accessedOn":"2026-11-03","supports":{"en":"Yogurt culture names; fermentation and coagulation. The consulted 2003 standard bears revisions 2008/2010; §2.1 pairs Lactobacillus delbrueckii subsp. bulgaricus with Streptococcus thermophilus."},"authors":["FAO/WHO Codex Alimentarius Commission"],"accessed":"2026-11-03","isPdf":true,"container":""},{"year":null,"url":"https://www.fao.org/4/t1265e/t1265e12.htm","institutionOrAuthor":"Food and Agriculture Organization of the United Nations","id":"src.yog.fao-starters","title":"Small-Scale Dairy Farming Manual, Volume 1: Technology Unit 10.1, Starter Cultures","container":"FAO","accessedOn":"2026-11-03","supports":{"en":"Starter culture; lactose converted to lactic acid; pure and mixed cultures."},"authors":["Food and Agriculture Organization of the United Nations"],"accessed":"2026-11-03"},{"year":null,"url":"https://golubcollection.berkeley.edu/late-19th-century-microscopes/","institutionOrAuthor":"The Golub Collection, University of California, Berkeley","id":"src.yog.golub","title":"Late 19th Century Microscopes","accessedOn":"2026-11-03","supports":{"en":"Institutional collection context and approximate dating of comparison instrument; no Grigorov ownership."},"authors":["The Golub Collection, University of California, Berkeley"],"accessed":"2026-11-03","container":""},{"year":2020,"url":"https://bibliotheque-russe-et-slave.com/Livres/Grigorov_-_Etude_sur_un_lait_fermente_comestible.pdf","institutionOrAuthor":"Stamen Grigorov (journal byline: Stamen Grigoroff)","id":"src.yog.grigoroff1905.reprint2020","title":"Étude sur un lait fermenté comestible. Le « Kissélo-mléko » de Bulgarie","container":"La Bibliothèque russe et slave, Littérature bulgare; electronic reprint of Revue médicale de la Suisse romande 25(10), 1905, pp. 714–721","pages":"1–13 (electronic edition)","accessedOn":"2026-11-03","supports":{"en":"Directly read later typeset reprint, not a journal facsimile. Bacille A is a long rod on PDF p. 4, whereas Stoilova p. 39 calls it a small rod. Rod shape and coagulation are supported; size adjective withheld pending facsimile comparison."},"authors":["Stamen Grigorov (journal byline: Stamen Grigoroff)"],"accessed":"2026-11-03","isPdf":true},{"year":null,"url":"https://transkotd.org/zabelezhitelnost/muzey-na-kiseloto-mlyako/","institutionOrAuthor":"Трънско туристическо дружество","id":"src.yog.local-museum","title":"Музей на киселото мляко","container":"Трънско ТД","accessedOn":"2026-11-03","supports":{"en":"Exhibition layout, household milk vessels, proximity to birthplace, opening date. Secondary local account; medical claims excluded."},"authors":["Трънско туристическо дружество"],"accessed":"2026-11-03","fieldLanguages":{"institutionOrAuthor":"bg","container":"bg"}},{"year":null,"url":"https://lpsn.dsmz.de/subspecies/lactobacillus-delbrueckii-bulgaricus","institutionOrAuthor":"Leibniz Institute DSMZ, LPSN","id":"src.yog.lpsn","title":"Lactobacillus delbrueckii subsp. bulgaricus","container":"List of Prokaryotic names with Standing in Nomenclature","accessedOn":"2026-11-03","supports":{"en":"Current name and distinction between discovery and later nomenclature. Scientific name details belong in evidence, not the reading body; subspecies is a smaller group within a species, a classification of organisms."},"authors":["Leibniz Institute DSMZ, LPSN"],"accessed":"2026-11-03"},{"year":2020,"url":"https://vle.upm.edu.ph/pluginfile.php/135226/mod_resource/content/1/%20Microscope%20%5BCompatibility%20Mode%5D.pdf","institutionOrAuthor":"University of the Philippines Manila, VLE; individual lecturer not identified","id":"src.yog.microscope-parts","title":"The Microscope","container":"University of the Philippines Manila teaching slides","accessedOn":"2026-11-03","supports":{"en":"Eyepiece, stage and reflecting mirror functions; general optics only, not provenance of historical instrument."},"authors":["University of the Philippines Manila, VLE; individual lecturer not identified"],"accessed":"2026-11-03","isPdf":true},{"year":null,"url":"https://www.pasteur.fr/fr/nous-connaitre/elie-metchnikoff-1845-1916","institutionOrAuthor":"Institut Pasteur","id":"src.yog.pasteur","title":"Elie Metchnikoff (1845–1916)","accessedOn":"2026-11-03","supports":{"en":"Metchnikoff worked at Pasteur Institute; Nobel recognition for immunity, not yogurt."},"authors":["Institut Pasteur"],"accessed":"2026-11-03","container":""},{"year":null,"url":"https://commons.wikimedia.org/wiki/File:Lactobacillus_delbrueckii_subsp._bulgaricus_in_yogurt.jpg","institutionOrAuthor":"Bondarev.gal","id":"src.yog.photo.bacteria","title":"File:Lactobacillus delbrueckii subsp. bulgaricus in yogurt.jpg","container":"Wikimedia Commons","accessedOn":"2026-11-03","supports":{"en":"Visual object identification and photographic licence only. 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."},"authors":["Bondarev.gal"],"accessed":"2026-11-03"},{"year":null,"url":"https://commons.wikimedia.org/wiki/File:Professeur_Metchnikoff,_portrait_du_scientifique_dans_un_laboratoire_de_recherche.jpg","institutionOrAuthor":"Agence Rol; restoration by Adam Cuerden","id":"src.yog.photo.laboratory","title":"File:Professeur Metchnikoff, portrait du scientifique dans un laboratoire de recherche.jpg","container":"Bibliothèque nationale de France / Wikimedia Commons","accessedOn":"2026-11-03","supports":{"en":"Visual object identification and photographic licence only. Metchnikoff with a microscope in a laboratory. Archival Agence Rol photograph restored by Adam Cuerden. It does not document Grigorov or his 1905 research."},"authors":["Agence Rol; restoration by Adam Cuerden"],"accessed":"2026-11-03"},{"year":null,"url":"https://commons.wikimedia.org/wiki/File:Elie_Metchnikoff._Photograph._Wellcome_V0026851.jpg","institutionOrAuthor":"Unknown photographer; Wellcome Collection","id":"src.yog.photo.metchnikoff","title":"File:Elie Metchnikoff. Photograph. Wellcome V0026851.jpg","container":"Wellcome Collection / Wikimedia Commons","accessedOn":"2026-11-03","supports":{"en":"Visual object identification and photographic licence only. Ilya Metchnikoff. Historical portrait from the Wellcome Collection; it does not document a meeting with Grigorov."},"authors":["Unknown photographer; Wellcome Collection"],"accessed":"2026-11-03"},{"year":null,"url":"https://commons.wikimedia.org/wiki/File:1870_circa,_binocular_compound_microscope,_Henry_Crouch,_England_-_Golub_Collection_of_Antique_Microscopes_-_DSC04870.JPG","institutionOrAuthor":"Daderot","id":"src.yog.photo.microscope","title":"File:1870 circa, binocular compound microscope, Henry Crouch, England - Golub Collection of Antique Microscopes - DSC04870.JPG","container":"Wikimedia Commons","accessedOn":"2026-11-03","supports":{"en":"Visual object identification and photographic licence only. Binocular microscope by Henry Crouch, England, about 1870. Museum photograph from the Golub Collection. A comparison object; not established as Grigorov’s microscope."},"authors":["Daderot"],"accessed":"2026-11-03"},{"year":null,"url":"https://commons.wikimedia.org/wiki/File:Museum_Studen_Izvor.jpg","institutionOrAuthor":"Krasimir Mihov","id":"src.yog.photo.museum","title":"File:Museum Studen Izvor.jpg","container":"Wikimedia Commons","accessedOn":"2026-11-03","supports":{"en":"Visual object identification and photographic licence only. 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."},"authors":["Krasimir Mihov"],"accessed":"2026-11-03"},{"year":null,"url":"https://commons.wikimedia.org/wiki/File:Sanitaren_maior_medium.jpg","institutionOrAuthor":"Unknown photographer","id":"src.yog.photo.portrait","title":"File:Sanitaren maior medium.jpg","container":"Wikimedia Commons","accessedOn":"2026-11-03","supports":{"en":"Identity and Commons licence declaration only. Anonymous photograph dated there before 1918. First publication date/place not established; rights unknown; withheld from story use."},"authors":["Unknown photographer"],"accessed":"2026-11-03"},{"year":null,"url":"https://commons.wikimedia.org/wiki/File:University_of_Geneva_2015.jpg","institutionOrAuthor":"Dmitry A. Mottl","id":"src.yog.photo.university","title":"File:University of Geneva 2015.jpg","container":"Wikimedia Commons","accessedOn":"2026-11-03","supports":{"en":"Visual object identification and photographic licence only. The University of Geneva photographed in 2015. City context; this building is not established here as the site of the 1905 laboratory."},"authors":["Dmitry A. 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