Water kefir is made with translucent crystals in sugared water: no dairy, no lactose, no caffeine, about 25 kcal and 1 to 4 g of sugar per 100 ml, ready in 24 to 48 hours and strongly fizzy. Milk kefir is made with white clusters in milk: about 55 kcal and 3 g of protein per 100 ml, ready in 18 to 30 hours, thick rather than fizzy, and usable in cooking. The two cultures are not interchangeable.
Both are called kefir, both are live reusable cultures, and there the similarity ends. Water kefir gives a drink close to a dry lemonade, milk kefir gives something close to drinking yoghurt. This page sets out the nine differences that actually change a decision.
The first row is the one people get wrong. These are two distinct communities of bacteria and yeasts, not one culture used two ways. Water kefir crystals placed in milk stop working, and white milk clusters placed in sugared water do the same. When buying, read the exact wording rather than the picture.
A sachet of freeze dried ferments is a third thing again. It lasts one to three transfers and then has to be bought anew. Real crystals and clusters last indefinitely and multiply.
| Per 100 ml | Water kefir | Milk kefir | Cola |
|---|---|---|---|
| Energy | about 25 kcal | about 55 kcal | about 42 kcal |
| Sugar | 1 to 4 g, by fermentation time | residual lactose, low | about 10 g |
| Protein | almost none | about 3 g | none |
| Calcium | none | from the milk | none |
| Fibre | 0 g | 0 g | 0 g |
| Caffeine | none | none | about 10 mg |
| Live cultures | yes | yes | none |
Water kefir is the lighter of the two by a wide margin, and that is its main practical argument as a replacement for a soft drink. Milk kefir is closer to a food than to a drink: it brings protein and calcium, which water kefir cannot.
| Room temperature | Water kefir | Milk kefir |
|---|---|---|
| 18 C | 48 to 72 hours | 30 to 36 hours |
| 22 C | 36 to 48 hours | 24 to 30 hours |
| 24 C | 24 to 36 hours | 20 to 24 hours |
| 28 C | 18 to 24 hours | 14 to 18 hours |
Milk kefir is faster per batch but needs daily attention, water kefir is slower but only needs handling every other day. Over a week the total time is almost identical, around fifteen minutes. The difference is how it is spread out.
If you want a visible result quickly, start with water kefir: two days and you know whether it works. If you cook and bake, start with milk kefir, because it replaces buttermilk, yoghurt and sour cream one for one. If you are unsure, start with water kefir and add the other one a month later.
The two procedures are close enough to run in parallel and different enough to be worth writing out. Neither needs equipment.
| Step | Water kefir | Milk kefir |
|---|---|---|
| 1 | dissolve 60 g sugar in 1 litre of unchlorinated water | 1 litre of fresh milk at room temperature |
| 2 | add 30 to 50 g crystals, a dried fig, a lemon slice | add 20 to 30 g grains |
| 3 | cover loosely, never sealed | cover loosely, never sealed |
| 4 | 24 to 48 hours at room temperature | 18 to 30 hours at room temperature |
| 5 | strain, keep the crystals | strain, keep the grains |
| 6 | second fermentation in a sealed bottle, 12 to 36 hours | usually not needed |
Step 6 is the only real divergence. Water kefir becomes properly sparkling only in a sealed swing top bottle, because the gas escapes from an open jar. Milk kefir thickens instead of fizzing, so bottling it under pressure mostly produces a separated layer.
The base never changes, the flavour goes into the second fermentation. A small amount per litre is enough, and the sugar in the fruit is food for the culture rather than an additive.
| Addition | Per litre | Result | Second fermentation |
|---|---|---|---|
| Fresh grated ginger | 1 teaspoon | sharp, very fizzy | 12 to 18 hours |
| Raspberries | a handful | fruity, deep red | 18 to 24 hours |
| Lemon and mint | 1 slice, 3 leaves | fresh, very light | 24 hours |
| Dried hibiscus | 1 teaspoon | tart, strongly coloured | 24 hours |
| Grape juice | 50 ml | sweeter, strongly fizzy | 12 hours |
Two rules keep the result predictable: change one ingredient at a time, and ferment sugary additions for less time because the pressure rises faster. A bottle of water kefir with grape juice should be opened briefly on the first day.
This is the honest argument for keeping the dairy version as well. Water kefir is a drink, milk kefir is also an ingredient.
| Use | Water kefir | Milk kefir |
|---|---|---|
| Drinking plain | ideal | possible, quite thick |
| Baking | liquid only, no body | replaces buttermilk one for one |
| Dressing and sauce | unsuitable | replaces yoghurt one for one |
| Smoothie | possible, very thin | good |
| Fresh cheese | impossible | 1 litre gives about 250 g |
| Marinade | acidity only | acidity and texture |
| Instead of a soft drink | ideal | unsuitable |
Read the first and last rows together and the division becomes obvious. Water kefir replaces what you drink, milk kefir replaces what you buy in cartons for cooking. They do not compete.
None of these ruins a culture permanently. Two or three normal batches with good water and enough food bring either one back.
After the single purchase of the culture, both come down to consumables. Water kefir needs sugar and a dried fruit, milk kefir needs milk.
| After 12 months | Water kefir | Milk kefir |
|---|---|---|
| Purchases of culture | 1 | 1 |
| Consumables per litre | 40 to 80 g sugar, 1 dried fig | 1 litre of milk |
| Packaging | the same bottles | the same jar |
| Culture at the end | roughly double | roughly double |
Water kefir crystals are small, translucent, jelly like grains. They are not a plant and not a fungus, despite the old household names. They consist of a scaffold of sugar chains that the bacteria build themselves, and inside that scaffold three groups of microorganisms work together.
| Group | What it does | What you notice |
|---|---|---|
| Lactic acid bacteria | turn sugar into acid | the tart taste, the falling pH |
| Yeasts | produce gas and aromas | the bubbles, the fruity note, alcohol traces |
| Acetic acid bacteria | work at the surface | a faint vinegary edge on long batches |
Because it is a community and not a single strain, the balance shifts with the surroundings. A warm summer favours the yeasts, a cool room the acid producers. The same water kefir therefore tastes different in July and in January, without anyone having made a mistake.
Whether you buy water kefir crystals or receive them from someone, five observations settle the question within 48 hours.
| Sign | In good shape | Needs reviving |
|---|---|---|
| Appearance | translucent, soft, elastic | grey, dry, crumbling |
| Smell | faintly sour, fresh | strongly yeasty or foul |
| Bubbles after 24 hours | present | none |
| Growth per week | visible | none |
| Batches until a rhythm | 1 | 3 to 6 |
Dehydrated crystals from a sachet fall into the right hand column. They do work, but they need five to ten days before they behave normally. That is the single most common reason someone concludes their water kefir has failed when in fact it has not started yet.
This comes up as soon as someone decides not to choose. It is entirely practical, with one precaution.
The total work for two cultures is around twenty minutes a week, against fifteen for one. That small difference is why most people who keep water kefir for six months end up with both.
Watch the pressure in the second fermentation. A sealed bottle left several days in a warm room can overflow or force its stopper. Open it briefly over the sink once a day until you know the rhythm of your kitchen.
Authorised health claims in the European Union are listed by the European Food Safety Authority. The nutritional figures above, by contrast, are on the label of every bottle you can compare them with.
Both cultures, one order
Live water kefir crystals and milk kefir grains, shipped hydrated and ready to use.
See the culturesThe step by step method: how to make kefir. Milk kefir in detail: what is milk kefir.
The culture and the base. Water kefir uses translucent crystals in sugared water and contains no dairy, no lactose and no caffeine. Milk kefir uses white clusters in milk and provides about 3 g of protein per 100 ml. The two cultures cannot be swapped.
Water kefir. A batch is drinkable after 24 to 48 hours, it tolerates mistakes more easily, and it needs attention only every other day.
No. It is made with water, sugar and a piece of dried fruit, so it contains no dairy and no lactose at all.
From about 6 g per 100 ml at the start, the figure drops to 3 or 4 g after 24 hours and 1 or 2 g after 48. It never reaches zero because the culture lives on it.
Yes. About a metre of distance and a cloth over each jar is enough. Yeasts travel through the air, and a water culture that picks up dairy yeasts changes flavour over several weeks.
Water kefir, clearly, provided the second fermentation happens in a sealed swing top bottle. Milk kefir thickens rather than fizzes.
Both produce traces during fermentation. Water kefir sits around 0.2 to 1 per cent, milk kefir usually under 0.5. A short, cool fermentation keeps the figure at the lower end.
Barely. It has no fat and no protein, so it adds acidity but no body. For dressings, sauces, batter and fresh cheese you need milk kefir.
