Buttermilk

A tangy, slightly thick cultured milk — the acidic, faintly sour dairy that makes biscuits fluffy, fried chicken juicy, and pancakes tender. Its lactic bite and thin-yogurt body do quiet work in almost every Southern kitchen.

What it is

The buttermilk you buy today is cultured buttermilk: low-fat or nonfat milk fermented with lactic-acid bacteria until it thickens and turns pleasantly sour. That acidity is the whole point in cooking — it tenderizes, adds tang, and reacts with baking soda to create lift. It’s thicker than milk but pours more freely than yogurt, and it carries a clean, buttery sourness. Despite the name, it’s low in fat, not rich or buttery in the fatty sense.

History & origin

The original buttermilk was traditional buttermilk — the thin, tangy liquid left behind after churning cream into butter. On farms, that leftover liquid had naturally soured from the wild bacteria in the cream, giving it its characteristic tang, and it was prized as a refreshing drink and a baking ingredient. As commercial dairies moved to sweet-cream butter and pasteurization, that byproduct largely disappeared from stores. Producers began deliberately culturing fresh milk to recreate the flavor and acidity, and cultured buttermilk became the standard product from the mid-20th century onward.

Where it comes from today

It’s made by nearly every commercial dairy, sold in cartons in the refrigerated milk section under brands like Kate’s, Organic Valley, and countless regional dairies. Cultured versions dominate North American and European markets. Fermented buttermilk-style drinks remain hugely popular worldwide too — chaas and sweet/salted lassi in South Asia, ayran in Turkey, and Nordic cultured milks like Finnish piimä — all part of the same tangy-cultured-dairy family.

How it’s used today

In baking it’s the acid that activates baking soda, so it’s central to buttermilk biscuits, buttermilk pancakes, cornbread, soda bread, and tender cakes. Its enzymes and acidity make it the classic soak for buttermilk fried chicken, seasoning and tenderizing the meat. It’s the base for creamy ranch dressing and buttermilk dressings, adds tang to marinades and mashed potatoes, and is enjoyed on its own as a cold drink in the American South and across South Asia.

Make your own

You can make a quick baking substitute by stirring 1 tablespoon of lemon juice or white vinegar into 1 cup of milk and letting it sit 5 to 10 minutes until it curdles slightly. True cultured buttermilk can be made at home by adding a few tablespoons of live cultured buttermilk to fresh milk and leaving it at room temperature until thickened. A from-scratch recipe is on the way.

Substitutes (if absolutely necessary)

• Milk + lemon juice or vinegar — 1 cup milk plus 1 Tbsp acid, rested 5–10 min; the go-to swap for baking, provides the acidity but not the body.
• Plain yogurt, thinned — whisk with a little milk or water to buttermilk consistency; adds tang and thickness, great in marinades and baking.
• Kefir — cultured and tangy like buttermilk; use straight across in most recipes.
• Cream of tartar + milk — stir about 1¾ tsp cream of tartar into 1 cup milk for the acid a recipe needs when you have no fresh acid on hand.

Where to find it

• Local store: the refrigerated dairy case beside the regular milk (Kate’s, Organic Valley, store brands).
• Online: grocery delivery services; buttermilk powder (SACO cultured buttermilk blend) is shelf-stable and available on Amazon for occasional baking.
• Make your own: stir 1 Tbsp lemon juice or vinegar into 1 cup milk and rest 5–10 minutes; or culture fresh milk with a splash of live buttermilk overnight.