How to Make Milk Kefir at Home

Milk kefir is a fermented milk drink made using kefir grains: small clusters containing bacteria and yeasts. When the grains are added to milk, they ferment part of the lactose and gradually turn the milk into a slightly sour, creamy drink.

Once you have active kefir grains, you can reuse them from one batch to the next. Healthy grains usually grow and multiply over time.

What are milk kefir grains?

Despite their name, kefir grains are not cereal grains. They are small, irregular clusters with a cauliflower-like appearance, made from a matrix of proteins and polysaccharides inhabited by bacteria and yeasts.

They are different from powdered kefir starter cultures. Traditional kefir grains can be strained out and reused repeatedly.

You can buy live grains from specialist fermentation suppliers. In Europe, one option is Wellness-Drinks in Germany. In the United States, Kombucha Kamp sells live milk kefir grains. Because healthy grains multiply naturally, they are also commonly shared by people who already make kefir.

What you need

• Milk kefir grains

• Milk

• A clean glass jar

• A lid

• A plastic, nylon or stainless-steel sieve

• A container for the finished kefir

You do not need specialist equipment. Dedicated kefir jars, such as those made by Kefirko, can make the process more convenient, but an ordinary glass jar works perfectly well.

Brief contact with stainless steel is fine. Reactive metals such as aluminium or copper are better avoided, particularly for prolonged contact with acidic fermented foods.

Which milk should you use?

Cow's milk and goat's milk both work well. Whole milk generally produces a thicker, creamier kefir, but semi-skimmed milk can also be used.

Traditional milk kefir grains are adapted to dairy milk. Plant-based drinks do not contain lactose and are therefore not a straightforward replacement if you want to maintain the grains over time.

How to make milk kefir

1. Add the grains to milk

Place the kefir grains in a clean glass jar and add fresh milk.

A useful starting point is roughly 1 tablespoon of kefir grains for 250–500 ml of milk.

This does not need to be exact. More grains, less milk and warmer temperatures will generally make fermentation happen faster.

2. Leave it to ferment

Place a lid loosely on the jar rather than sealing it tightly. Leave it at room temperature and out of direct sunlight.

Fermentation often takes around 18–24 hours, but the appearance matters more than the clock. The milk should begin to thicken and develop a pleasantly sour smell. You may see small pockets of clear or yellowish whey forming between the thicker milk.

A milder kefir can be strained earlier. A longer fermentation gives a stronger, more acidic result.

3. Strain the kefir

Pour the kefir through a sieve and gently stir or shake it until the liquid has passed through and the grains remain behind.

There is no need to routinely rinse the grains between batches.

4. Start again

Put the grains back into a clean jar, add fresh milk and repeat the process.

After a few batches, it becomes much easier to judge the kefir by appearance, smell and taste rather than by a fixed number of hours.

Storing your kefir

Keep the finished kefir in a closed container in the refrigerator.

Fermentation slows considerably when chilled, although it does not stop completely, so the kefir may gradually become more acidic.

If you want to take a break from making kefir, place the grains in fresh milk in a covered jar in the refrigerator. When you want to restart, strain them, add fresh milk and return them to room temperature. After a longer break, they may need one or two batches before becoming fully active again.

What to do when the grains multiply

Healthy kefir grains often grow over time. If you keep adding all of them to the same amount of milk, fermentation gradually becomes faster.

Remove some when you have more than you need. You can give them to someone else, keep some as a backup, or eat them. Kefir grains are edible, although their soft, slightly rubbery texture is unusual.

Troubleshooting

The kefir separates into curds and yellowish liquid

It has probably fermented longer than necessary. This is usually normal. Strain or stir it as usual, then shorten the next fermentation, use more milk or reduce the amount of grains.

The kefir is fermenting very quickly

The room may be warmer than usual, or the grains may have multiplied. Use more milk, remove some grains or shorten the fermentation time.

The kefir stays thin

Give it more time, especially in a cool room. Grains that have recently been refrigerated or transported may also need several batches before becoming fully active again.

There is a flat or wrinkled white film on top

This can sometimes happen when surface yeasts become more dominant, particularly after repeated long or warm fermentations. Strain the grains, add fresh milk and place them in the refrigerator for a short period before returning to your normal routine.

There is fuzzy or hair-like growth

Discard both the kefir and the grains. Fuzzy growth can indicate mould and is not something to try to rescue at home.

There are coloured patches

Pink, orange, green, blue or black growth is not normal. Discard the kefir and grains.

The smell is clearly wrong

Kefir naturally smells sour and slightly yeasty, and this can vary from batch to batch. A rotten or distinctly unpleasant smell is a reason to discard it.

A few practical questions

Do I need to wash the grains?

No. Routine rinsing is unnecessary. Strain them and transfer them directly into fresh milk.

Can I use lactose-free milk?

Fermentation becomes less predictable because traditional kefir grains normally rely on lactose as an important substrate. If you want to maintain vigorous grains over time, regular dairy milk is the simplest option.

Fermentation reduces some of the lactose in milk, but finished kefir should not automatically be considered lactose-free.

Is separated kefir still usable?

Usually, yes. Separation into thicker curds and yellowish whey generally means fermentation has progressed further. That is different from coloured or fuzzy surface growth.

Food safety

Use clean jars and utensils, use fresh milk, and discard kefir if you see obvious mould, unusual colours or signs of spoilage.

Milk kefir remains a dairy product. It is not suitable for people with a milk-protein allergy, and home-fermented foods may require extra caution in people who are severely immunocompromised. During pregnancy, consuming unpasteurized fermented foods is not recommended.