Milk kefir problems and how to fix them

First question: are the grains new?

For the first one to three batches after the grains arrive, kefir is often thin, sometimes a bit yeasty and uneven in taste. The grains have been through the post and are adjusting to your milk and your kitchen. That is not a problem, just a settling-in period. Keep to the 24-hour rhythm and give them fresh whole milk every day. Within a week the kefir should be as it ought to be.

If your jar has been running well for months and something suddenly changes, ask yourself what else changed. A cold snap or a heatwave? A different milk because the usual one was sold out? The jar moved to another shelf, a break in the fridge, more grains than before? The answer is almost always there.

The milk will not set

After 24 hours the milk is still liquid, hardly smells sour and looks much the same as when you poured it.

Usually because:

• The grains are new, or have just come out of the fridge.
• The kitchen is below 20°C, which in a British winter is more the rule than the exception.
• There are too few grains for the amount of milk.
• The milk is skimmed or semi-skimmed, or a plant drink.

What helps: a warmer spot (a shelf in or near the airing cupboard works wonders), whole milk, and checking the ratio of 20 g per litre. If that is not enough, use a little less milk for a few batches. A thin batch can safely be left a few hours longer. How to steer the thickness further is in Milk kefir too thin or too thick?

The kefir separates into curds and whey

You see a layer of clear, yellowish liquid at the bottom or in pockets through the kefir, with thick lumps above it. That is whey and curd: the kefir has gone past its best point.

Usually because: too warm, too long or too many grains. In summer it can happen after only 18 hours.

What helps: strain earlier, find a cooler spot, or take some of the grains out. Separated kefir has not gone off. Shake or whisk it for a thick drinking kefir, or drain it in a cloth for strained kefir cheese. It is also exactly what you want in a batch of scones.

Too sour

Usually because: too many grains for the milk, or left too long or too warm. Grains grow, so what was right a month ago may be too much now.

What helps: weigh the grains and go back to 20 g per litre, strain earlier, move the jar somewhere slightly cooler. Sour kefir is no loss in the kitchen: in scones, pancake batter, a lemon drizzle or a marinade it does a fine job, just as sour buttermilk would.

A strong smell of yeast, or a faint beery note

A light yeasty note is normal, a bit like bread dough. If your kefir smells strongly of yeast, or even a little of beer, the yeasts have taken over.

Usually because: the grains have just travelled or are coming out of a long break, or the kefir stood long and warm, for example during a second fermentation in a closed bottle.

What helps: fresh whole milk every day and a strict 24 hours. Leave out the second fermentation for a while. After a few batches it settles down.

Stringy or slimy kefir

A slightly syrupy kefir that pulls into strands is simply the character of some grains. If it turns properly slimy when it never used to, the balance has been upset.

Usually because: heat, a change of milk or a long break.

What helps: a few batches on whole cow's milk, exactly 24 hours, in a spot between 20 and 25°C. Swirl the grains once in cold, fresh milk.

The grains are not growing, or getting smaller

Usually because:

• Rinsing under the tap.
• Skimmed milk, semi-skimmed milk or plant drinks.
• Repeated heat, or long spells without fresh milk.
• Pressing hard in the sieve.

What helps: stop rinsing, use whole milk, keep a steady rhythm and a light hand with the spoon. In the first weeks grains often hardly grow at all, which is normal. More on daily care in Caring for milk kefir grains.

The grains have turned yellow or limp

Grains in good form are white to cream and firm. A yellowish tint often comes from the milk or from a long batch where the grains sat in whey. Swirl them in a little fresh milk and after a few batches they will be pale again. If they stay limp and fall apart, look at the milk and the temperature.

The kefir tastes bitter or musty

Usually because: milk that was already close to its date, a jar with traces of soap, or a batch that stood far too long. Sometimes a jar in the fridge picks up the smell of what is next to it.

What helps: fresh milk, a well-rinsed jar and a lid on the jar in the fridge. If the smell is truly rotten or you see discolouration, do not carry on with that batch.

Mould or not?

Mould is rare with milk kefir, because the kefir sours quickly. Even so, it helps to know what is normal and what is not, particularly in a damp house in a mild, wet autumn.

If you see real mould, throw away the kefir and the grains, and send us a photo so we can work out together what happened. With fresh milk kefir grains you will have a new batch going within 24 hours of the parcel arriving.

Everything at a glance

Which milk gives which kefir is covered in Which milk for kefir?, and the slips nearly everyone makes at the start are listed in Beginner kefir mistakes.

Frequently asked questions

For every other question about your grains, the complete milk kefir guide has the answers. And if you want to start afresh, our live milk kefir grains are available from £14.