Dahi
What it is
Dahi is Indian yogurt: traditionally thicker, denser, and more sharply sour than most Western yogurt, often set from buffalo milk and therefore richer. It is the everyday cultured-milk staple of the subcontinent, eaten as is, churned into drinks, and cooked into sauces.
How it's made
Warm milk is inoculated with a spoonful of an existing batch of dahi (the live culture) and left to set undisturbed in a warm place overnight. Indian household cultures are typically a mixed, ambient population dominated by lactic-acid bacteria that yield a thicker set and a more pronounced tang than the controlled two-strain commercial yogurts of the West. Buffalo milk, with its high fat and solids, sets especially firm.
Flavor profile
Tangy and sour, with the depth of sourness depending on how long it sets; rich and thick in mouthfeel, especially when buffalo-milk based. Hung (strained) dahi becomes thick and spreadable, approaching labneh.
Culinary uses
Dahi is whisked into raita (with cucumber, boondi, or spices), thinned and spiced into chaas and lassi, cooked with gram flour into the sauce base of kadhi, used to marinate meats for tandoori and biryani (its acidity and enzymes tenderize), and eaten with rice as a cooling end to a meal (curd rice). Hung curd makes the base of dips and some sweets (shrikhand).
Regional variations
Buffalo-milk dahi (north and west) is thicker and richer; cow-milk dahi is lighter. Mishti doi of Bengal is a sweetened, caramel-tinged baked yogurt set in clay pots. South Indian curd tends to be tangier and is central to curd rice and the buttermilk drink neer mor.
Cultural & historical context
Yogurt is ancient across South and Central Asia and carries auspicious meaning — a spoonful of dahi (often with sugar) is eaten before journeys and exams for good luck. It is also a cornerstone of Ayurvedic eating. Why substitution fails: thin, mild Western yogurt added to a hot kadhi or curry will curdle and lacks the body and tang the dish expects; the standard fix (tempering with flour or never boiling) exists precisely because Indian recipes assume a thicker, more robust dahi.
Reference notes
Tags: `yogurt`, `cultured`, `buffalo-milk`, `tangy`, `marinade`. Related ingredients: lassi, chaas, labneh, Bulgarian yogurt, malai. Related cuisines: North Indian, South Indian, Bengali. Suggested links: Lassi, Chaas, Raita, Kadhi, Mishti Doi.