Milk kefir, the twenty-second ferment

Milk kefir is fermented milk made with kefir grains — soft, cauliflower-like clusters of bacteria and yeast held together in a protein matrix. They are not a starter powder. They are a living colony that grows, and with minimal care will outlive most kitchen appliances.

What you need

• 1 tablespoon of live kefir grains. Buy dehydrated ones or, better, take a spoonful from someone already brewing.
• A glass jar, a plastic or nylon strainer, a wooden or silicone spoon. Prolonged contact with reactive metal weakens grains; brief stainless-steel contact is fine.
• Whole milk. Cow, goat or sheep. UHT works but produces a duller result.

Method

1. Put the grains in a jar and add 250 ml of milk — roughly 1:20 grains to milk by volume.
2. Cover with cloth or a loosely rested lid.
3. Leave at room temperature, 18–25 °C, for 12 to 24 hours.
4. It is done when it has thickened, smells tart and clean, and pulls away from the jar in a soft set. If you see clear whey pooling at the bottom, it has gone slightly far — still drinkable, just sharper.
5. Strain into a bottle, stirring gently to push the kefir through. Return the grains to a clean jar with fresh milk immediately.

The whole daily operation takes under a minute.

Adjusting

• Too sour? Shorter ferment, cooler spot, or more milk per spoon of grains.
• Too thin? Longer ferment, or fewer grains removed.
• Grains growing fast? They should roughly double every few weeks. Eat the excess, give it away, or blend it into a smoothie.

Second ferment

Bottle the strained kefir with a strip of lemon peel, a split vanilla pod or a spoon of fruit, seal, and leave at room temperature for 8 to 24 hours. It becomes slightly effervescent, less sharp, and noticeably better. Refrigerate afterwards.

Pausing

Going away? Put the grains in a jar with plenty of fresh milk and refrigerate. They will hold for two to three weeks, and may need a couple of ordinary cycles afterwards to come back to full strength. Do not freeze unless you plan to be away for months.

What it is good for

Kefir carries a broader range of microbes than commercial yoghurt, and the ferment consumes most of the lactose, which is why people who avoid milk often manage it comfortably. Beyond drinking it: use it in place of buttermilk in pancakes, as a marinade for chicken, whisked into cold soups, or strained through cloth overnight into a soft cheese.

Nutrition claims around fermented dairy run far ahead of the evidence. What is defensible: it is a cheap, low-waste way to turn ordinary milk into something more interesting, using a culture you never have to buy twice.