Fermented milk

It is milk soured by live microbes, usually lactic-acid bacteria, which give it a tangy flavour and thicker texture. The term covers several foods, including cultured milk and kefir; they are not all made with the same cultures.

Yes. Use the same amount in pancakes, soda bread or scones: its acidity helps bicarbonate of soda raise the mixture and adds a gentle tang. If it is very thick, thin it with a little milk until it pours like buttermilk.

It can split if boiled. Take the pan off the heat, let it cool briefly, then stir in fermented milk; for a smoother sauce, whisk a spoonful of the warm sauce into it first.

Use it in a smoothie with berries or banana, pour it over porridge, or blend it with cucumber, garlic and herbs for a savoury dressing. For an ayran-style drink, whisk it with cold water and a pinch of salt.

Usually, in cold sauces, marinades and smoothies, though the flavour and thickness may differ. For a recipe that needs a thick, spoonable yoghurt, strain runnier fermented milk through clean muslin in the fridge until it reaches the consistency you need.

Keep it covered in the fridge and use a clean spoon or pour directly rather than drinking from the container. Follow the product’s storage instructions after opening; discard it if you notice mould, an unusual smell or a change in texture beyond its normal tang.

You can freeze it in a sealed container, leaving room for expansion, but thawing may make it grainy or separated. Stir it well and use it in baking, smoothies or cooked dishes rather than expecting its original texture.

No: kefir is one kind of fermented milk, made with a culture that includes bacteria and yeasts. Other fermented milks may use bacterial cultures only, so their tang, thickness and slight fizz can differ.