Ingredient

Soured cream

Soured cream is cream cultured with bacteria until it thickens and turns tangy. It is lower in fat than crème fraîche and higher in acid, and those two facts together explain its one real problem: it splits in a hot pan far more readily than anything else in the chiller cabinet.

Why fat and acid decide everything

Dairy splits when its casein proteins clump together and squeeze out the water they were holding. Two things push them towards that: acidity, which brings the proteins closer to the point where they coagulate, and heat, which gives them the energy to do it.

Fat is what protects against it. Fat globules physically get in the way of proteins finding each other, so a higher-fat dairy product tolerates far more heat before it breaks.

That gives a clear order. Double cream, very high in fat and barely acidic, can be boiled hard with impunity. Crème fraîche, high in fat and cultured, is very forgiving. Soured cream, typically around eighteen per cent fat and distinctly acidic, splits readily. Yoghurt and kefir, lower in fat and more acidic still, split almost immediately.

So when a recipe says to add soured cream off the heat, it is not being fussy. It is the one instruction that keeps a stroganoff from looking curdled.

How to stop it splitting

Any one of these helps; two or three together make it reliable.

• Take the pan off the heat first, and let it stop bubbling before the cream goes anywhere near it.
• Temper it. Stir a few spoonfuls of the hot liquid into the soured cream in a separate bowl, then return the loosened mixture to the pan. It never meets a temperature shock.
• Stabilise it with starch. Whisk a teaspoon of flour or cornflour into the soured cream before it goes in. The starch gets between the proteins and physically stops them clumping — this is the most robust fix and it is what many classic recipes quietly rely on.
• Use full-fat. Reduced-fat soured cream splits much more easily, because fat is the protection.
• Never let it boil, at any point, after it has gone in.
• Or use crème fraîche instead, which will take a boil and is the sensible swap for a dish you cannot babysit.
• If it has already split, it is a cosmetic failure rather than a spoiled dish. Blending it or whisking hard off the heat will often bring it back.

Soured cream against its neighbours

Soured cream

Around 18% fat, cultured, distinctly tangy. Splits readily with heat. For dolloping, dipping and finishing off the heat.

Crème fraîche

Around 30–40% fat, cultured, milder and richer. Can be boiled. The one to use when a sauce needs to simmer.

Double cream

Around 48% fat, not cultured, sweet. Boils without splitting. No tang at all.

Greek yoghurt

Around 10% fat, more acidic. Splits easily. Closest substitute for soured cream in a cold application.

Buttermilk

Low fat, high acid, thin. A different thing entirely — see buttermilk.

Substituting

Crème fraîche for soured cream works everywhere and is richer and less tangy. Greek yoghurt works cold. Neither is exact.

What to use it in

• On baked potatoes, chilli, tacos and soup, cold, as a dollop. Its acidity is doing the same job a squeeze of lime would.
• In stroganoff, off the heat, stabilised with a little flour.
• In dips, with chives, onion, or blended with herbs.
• In baking — soured cream cakes and coffee cakes, where the acid reacts with bicarbonate of soda and the fat keeps the crumb tender.
• In Eastern European cooking, where it is a staple rather than a garnish: stirred into borscht, goulash, mushroom dishes and dumplings.
• In a dressing, thinned with milk or buttermilk.
• In scones and soda bread, where it substitutes for buttermilk with extra richness.
• Not in anything that will boil, unless you have stabilised it.

Common questions