Food

Yogurt

Also known as: Yoghurt, Yaourt

Cultured milk fermented by lactic-acid bacteria — typically Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus working in symbiosis. Documented across Central Asia, the Middle East, the Caucasus, and the Mediterranean for at least 5,000 years. Likely originated when milk stored in animal-skin containers in warm climates was inoculated by environmental bacteria. Made fresh daily in many traditional households; provides protein, calcium, B vitamins, and live cultures that contribute to gut microbiome diversity. Greek-style strained yogurt, Bulgarian yogurt, Turkish süzme, Indian dahi, and dozens of regional variants exist.

How yogurt is made

Heat milk — typically to ~180°F to denature whey proteins (this thickens the final yogurt) and pasteurize
Cool to inoculation temperature — ~110°F, the optimal range for the bacteria
Inoculate — add a small amount of previous yogurt or commercial culture
Hold at ~110°F for 4–12 hours — the bacteria multiply, produce [[lactic-acid|lactic acid]], lower the pH, and thicken the milk
Cool and refrigerate — fermentation slows; texture continues to develop

The two organisms work in symbiosis: [[yogurt-culture|Streptococcus thermophilus]] grows fastest at the start, lowering the pH; Lactobacillus delbrueckii picks up as the Streptococcus slows, finishing the acidification and producing characteristic flavor compounds.

Traditional and regional variations

Greek / strained yogurt — yogurt strained to remove whey; thicker, higher protein
Bulgarian yogurt — traditionally heirloom strains specific to the region; longer fermentation
Skyr (Iceland) — extra-strained, very thick; distinct cultures including [[yogurt-culture|Streptococcus thermophilus]] and Lactobacillus with traditional secondary microbes
Süzme (Turkish) — strained yogurt, often used as a thicker spread
Dahi (Indian) — wild-fermented at room temperature with whatever lactic-acid bacteria are present locally; more variable, often more sour
Filmjölk, viili, tarag — Scandinavian, Finnish, and Mongolian traditional yogurt-related ferments using mixed cultures with different yeasts and molds

Live cultures

Industrial yogurt manufacturing typically pasteurizes after fermentation (killing the cultures) for shelf stability. Live-culture yogurt is preferable for microbiome benefits; raw-milk yogurts and home-cultured yogurts are most-microbially-diverse.

Home practice

Yogurt is among the easiest dairy ferments. The minimum requires only milk, a starter (a tablespoon of live yogurt), and a way to maintain ~110°F for 4–12 hours (oven on lowest setting with light, dedicated yogurt maker, insulated container, or instant pot).

Sources

[[the-art-of-fermentation|The Art of Fermentation]], [[sandor-katz|Sandor Ellix Katz]]
Wild Fermentation, [[sandor-katz|Sandor Ellix Katz]]
Yogurt: Roles in Nutrition and Impacts on Health, Sharma & Kanwar eds. (CRC Press, 2017)

Rooted in life.

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Cultural

shares approach with

Kefir both are cultured-milk fermentations; kefir uses mixed-culture grains rather than yogurt's two-species starter; kefir is more biologically complex

1 inbound link · 3 outbound