Actually very easy

Kefir

The beliefKefir is taken for a runnier yoghurt, or for something that needs a machine.

The truthDrop the grains into milk, leave them a day at room temperature and strain. The grains come back every time.

Five minutes of work, twenty-four hours of waiting

How to make it

What you need

1–2 tablespoons of kefir grains
500 ml full-fat milk at room temperature
A glass jar and a plastic sieve

How the engine read this list (2 lines)

—	Kefir grains	no record
515 g	Full-fat milk	milk

An empty weight means that line could not be turned into grams — either the amount is open ("to taste") or the ingredient has no record here. Neither enters the sum as zero; they do not enter it at all.

Put the grains in a glass jar and pour the milk over them, leaving the jar a third empty: fermentation makes gas.
Do not seal it. Cover the jar with cloth or kitchen paper held by a band — a closed jar builds pressure.
Leave it at 20–25 °C out of direct sun for 18 to 24 hours. A warm kitchen may finish in 12, a cool room can take 36.
When it thickens and starts pulling away from the glass, strain it through a plastic sieve. Brief contact with metal is harmless; long contact is not.
Return the grains in the sieve to fresh milk and carry on. A further day in the fridge softens the finished kefir.

Why it works

Kefir differs from yoghurt in two fundamentals. First, temperature: yoghurt culture is thermophilic and wants 42–45 °C, while kefir’s is mesophilic and works at 20–25 °C — ordinary kitchen warmth, with no heat source required. Second, the cast: yoghurt has two bacteria, while a kefir grain holds dozens of bacteria and yeasts together inside a gel matrix of casein and sugars. The yeasts make kefir lightly carbonated and faintly alcoholic, usually under 0.5%, while the bacteria take the pH down to about 4.4. The grain itself is never consumed; it is a symbiotic colony and it grows with every ferment. For the same reason kefir is not a product but an ongoing culture — the grain is the last thing you ever buy.

The rough sum

515 grams going in

314 kcal in total

100% of the mass has figures behind it. This is the sum of what GOES IN rather than of what comes out. Wherever something evaporates, drains or ferments the two differ: a kilo of milk is 150 g of cheese.

Diets it qualifies for

Gluten-free Vegetarian

Storage & shelf life

How long it keeps

Strained kefir, in the fridge: 1 week
Grains in milk, in the fridge: 2 weeks
Grains dried: 6 months
Strained kefir at room temperature: 1 day, then it sharpens

Kefir keeps working in the fridge, only more slowly: a little sharper and a little fizzier each day. In a sealed bottle the pressure builds, so loosen the cap now and then. Clear liquid separating on top is whey rather than spoilage — shake it back in. Healthy grains look like cauliflower, elastic and white; yellowed, disintegrating or slimy grains mean the feeds have been left far too long.

When to bin it Fuzzy, coloured mould on the grains or the surface means both the kefir and the grains go. Kefir smells sharp and yeasty, which is normal; mouldy smells and coloured patches are not.

History

Where it comes from

Kefir comes from the Caucasus, where the grains were valuable enough to count as family property — passed down as inheritance or included in a dowry. It spread through Turkey mainly in the last twenty years, but its logic is not foreign here: from yayık ayranı to tarhana, souring milk into something that keeps is a basic reflex of this kitchen. What sets kefir apart is the yeast in the cast, which makes it a relative of boza and şalgam rather than of ayran. Its faint fizz is not a fault but part of the definition.

The knack

The grains multiply. Feed the surplus in a second jar as a backup, or pass it on — throwing it away is a waste.
Do not feed them flavoured, sweetened or lactose-free milk. The grains live on lactose and weaken without it.
For a break, put the grains in milk in the fridge: they hold for two weeks and recover after two feeds.

Milk and culture