Milk fermented by bacteria that turn its sugar into lactic acid, which sets the protein into a gel and preserves it — and makes it digestible to people who cannot drink milk.
Where it comes from
Yoghurt belongs to a broad belt running from the Balkans through Anatolia, the Levant, the Caucasus, Iran and Central Asia to South Asia, where it is a daily food rather than a breakfast item. The word is Turkish; the practice is older than any of the names for it.
The two organisms in classic yoghurt, Lactobacillus bulgaricus and Streptococcus thermophilus, work together — each produces compounds the other needs — which is why yoghurt culture is passed on as a culture and not assembled from scratch.
The related soured milks are their own foods, not near-misses: kefir is fermented by a symbiotic community of bacteria and yeasts and is faintly fizzy and alcoholic; skyr, labneh and chakka are all strained to different degrees.
Varieties
- Plain set yoghurt — Fermented in the pot, so the gel is unbroken.
- Stirred / Greek-style — Strained of whey to concentrate it. Thicker, higher in protein, more acidic.
- Labneh — Strained much further, to a soft cheese. Rolled in oil and herbs, or spread.
- Skyr — Icelandic, technically a fresh cheese, strained very hard and very low in fat.
- Kefir — Fermented with grains of bacteria and yeast. Thinner, sharper, slightly effervescent.
- Dahi and chaas — South Asian set yoghurt and its thinned, salted drinking form.
- Ayran, doogh, lassi — Salted or sweet yoghurt drinks from Turkey, Iran and South Asia.
In the kitchen
Yoghurt curdles when heated because its proteins are already acid-destabilised. Stabilising it — with a little cornflour, or by tempering it with hot liquid before it goes in — is standard practice in every cuisine that cooks with it, and it is why Turkish and Persian yoghurt soups do not split.
Its acid tenderises meat surfaces and, more importantly, carries fat-soluble spice flavours into them, which is what a yoghurt marinade is actually doing.
To make it: milk heated to about 85°C and cooled to about 45°C, a spoonful of live yoghurt stirred in, held warm for several hours. The heating is what makes it set thick, by denaturing the whey proteins first.
Dishes with yoghurt
ChakaStrained sour yoghurt beaten with dried mint and garlic, spooned over rice and breadPakistanKadhi PakoraTangy yoghurt and gram-flour gravy holding fried onion fritters, ladled over riceMongoliaTaragThick soured yoghurt from cow, yak or camel milk, eaten by the bowl
Qurutobflatbread torn into kurut-yogurt sauce with onions; national dish, shared
BuredziciSmall burek rolls baked then drowned in garlicky yoghurt and butter.JordanLabnehstrained yoghurt eaten with olive oil, za'atar and cucumber at breakfastNamibiaOshikandelaSweetened cultured drinking yoghurt sold in flavoured sachetsYoghurt is tagged on 148 dishes from 68 countries in the atlas. These notes are written from general knowledge and carry no per-fact citation — see About.