Milk kefir is one of the gentlest fermentations there is: three ingredients, twenty-four hours of patience, and no equipment beyond what you probably already have in the kitchen. If you've been hesitant because you imagined a complicated process, the daily routine takes about two minutes. Here is the guide I wish I had when I started.
What you'll need
Most of these you already have. The only thing you need to source is the grains themselves.
- Live milk kefir grains: 20-30 g is enough to start. Real grains look like small white cauliflowers, not powder.
- Whole milk, pasteurized or UHT. Organic if you can — the grains appreciate it and the flavor is better.
- A glass jarof at least 500 ml. Clean, but don't sterilize it with bleach (chlorine residue is bad for the grains).
- A plastic strainer with mid-sized holes. Avoid stainless steel for prolonged contact with the grains.
- A cotton cloth and a rubber band to cover the jar during fermentation.
Step-by-step
1. Put the grains in the jar and add milk
Drop the grains into your clean glass jar and pour the milk in, following a rough ratio of 1 part grains to 10 parts milk by weight. To start, give the grains a generous amount: 30 g of grains in 300 ml of milk. More grains means faster fermentation and tangier kefir.
2. Cover and leave at room temperature
Cover the jar with a cotton cloth fixed by an elastic band. Leave it at room temperature, away from direct heat sources and sunlight. Ideal temperature is 20°C-25°C — fermentation is faster in summer, slower in winter.
Don't seal it tightly. Kefir produces a small amount of gas and the yeasts need a tiny bit of air exchange.
3. When ready: filter and start over
After 18-24 hours you'll see the milk thicken and start to separate slightly into two layers: a creamy white layer (the solids) and a yellowish layer (whey). That's the signal it's ready.
- Pour the contents through a plastic strainer.
- Stir gently with a spoon to push the liquid through. The filtered kefir collects in another container — that's your drink.
- The grains stay in the strainer. Optionally rinse them briefly (not required), then return them to the jar.
- Add fresh milk and start over. Drink the filtered kefir immediately or store it in the fridge for a couple of days.
How long should it ferment?
It depends on temperature, grain ratio, and personal taste:
| Condition | Indicative time |
|---|---|
| Summer, 25°C, 1:8 grain-to-milk | 14-18 hours |
| Average room temperature, 20°C | 20-24 hours |
| Winter, cool kitchen (16°C) | 30-36 hours |
The most reliable way to know it's ready is to look: when the milk is clearly thickened and a yellow whey line is starting to separate, filter. If you taste and it's too sour, filter earlier next time. If it's still thin and sweet, give it another hour.
Common beginner mistakes
Things I did wrong, so you don't have to.
- Using metal in prolonged contact.A spoon or steel strainer for a few seconds is fine, but don't leave grains in metal containers for hours.
- Sealing the jar tightly. Pressure builds up and fermentation gets weird. Loose lid or cloth + elastic band.
- Rinsing with chlorinated tap water. Milan tap water has chlorine that weakens grains. Use bottled water if you rinse, or skip the rinse.
- Letting it ferment way too long «to be safe».Beyond 36 hours grains start to suffer from milk depletion. Filter and feed them fresh milk.
What to do with fresh kefir
Drink it as is — cold, maybe with a spoon of honey and a sprinkle of cinnamon. Or use it for breakfast recipes like smoothie bowls and pancakes.
For a fizzier kefir, do a second fermentation: seal filtered kefir in a bottle with a piece of orange peel or a ginger slice and leave it 12-24 hours at room temperature. It becomes effervescent and slightly sweeter, almost like a kefir-champagne.
Once your grains start multiplying (which they will, within 2-3 weeks), you'll have more kefir than you can drink. That's the moment to learn how to manage growing grains long term.
Frequently asked
Can I make kefir without grains?+
Not really. Freeze-dried starter sachets exist, but they produce a different drink with fewer strains and need to be replaced after a few batches. Real live grains multiply themselves indefinitely.
What milk works best?+
Whole pasteurized milk, organic if possible. UHT also works. Avoid lactose-free or extensively microfiltered milks — they sometimes don't ferment properly.
Do I need to seal the jar tightly?+
No. Cover loosely with a cloth or place a lid on top without screwing it down. Kefir produces a small amount of CO₂ and the yeasts need a little air exchange.
