Interactive lesson

Kefir and soured milk, step by step

Interactive lesson: milk that sours on the kitchen table — safe milk, kefir from grains, looking after the grains, mesophilic soured milk, ayran, kefir cheese and tarhana.

Free sample Chapters 1 and 2 (8 steps) are free. The full lesson comes with the Soured milk and fermented dairy module. Already bought? Unlock

This lesson is general guidance, not professional training. Local regulations and expert advice always take precedence. Read our disclaimer.

The whole lesson as text

1. Milk and safety

Kefir and mesophilic soured milk work at room temperature, but the milk is always heated first.

Heat the milk — To 85 °C (185 °F), 90 °C is fine too, or bring it to the boil. For kefir, 72–75 °C (162–167 °F) for at least 1 minute, stirring all the time, is also enough.
Cool it quickly — In cold water, to 20–25 °C. The milk mustn't stand lukewarm for long.
Shop milk — Pasteurised or UHT milk can be used without heating. Just warm it or cool it to room temperature.
Milk from treated animals — It doesn't go into ferments until the withdrawal period is over. Antibiotics kill the culture, and the milk isn't fit to eat.

Why: At 20–25 °C (68–77 °F) the bacteria in raw milk that cause illness grow too: listeria, E. coli, staphylococci. For the first few hours the culture can't stop them. So the rule is the same as for yoghurt.

"Leave the milk to sour by itself" is not a recipe. Raw milk then sours from whatever bacteria happen to be in it.
Pregnant women, small children, older people and anyone who is ill don't eat ferments made from raw milk.

2. Kefir from grains

Kefir grains are white, rubbery lumps that look like tiny cauliflower florets.

Grains into the jar — For 1 L of kefir, 20–50 g of grains (1–3 tablespoons). Put them in a clean 1.5 L glass jar.
Pour over the milk — Milk at 20–25 °C, to three quarters of the jar. Cow's, goat's or sheep's.
Cover and wait — Cover with muslin or a loose lid. Leave 18–24 h at 20–25 °C, out of the sun.
Strain — Through a plastic or stainless steel sieve, stirring with a wooden or plastic spoon. Don't rinse the grains with water; put them straight into fresh milk.

Why: The grains are a community of lactic acid bacteria and yeasts. They can't be made from scratch; you get them from someone who has them, and they grow from batch to batch.

Fewer grains means slower, milder kefir.
Kefir from a sachet is made the same way, with the culture as directed on the sachet. For the next batch, keep back 2–3 tablespoons of finished kefir per 1 L.