Kefir: the complete guide to milk kefir, water kefir and living kefir grains

1

What kefir is

A tangy, lightly effervescent cultured milk with roots in the northern Caucasus, made with a living culture that has been passed hand to hand for more than a thousand years.

Kefir (say keh-FEER) is a sour, drinkable cultured milk, a little like buttermilk but livelier. The name is usually traced to the Turkish word keyif, which loosely means pleasure or feeling good, a nod to the sense of wellbeing people have long associated with drinking it.

Its flavour is complex. Researchers have identified around forty aroma compounds in kefir, and fermentation leaves a trace of natural alcohol, usually well under 1% in freshly strained kefir, along with a gentle fizz from carbon dioxide. What makes kefir unusual among cultured milks is its starter: kefir grains, a self-renewing mother culture that grows as it ferments.

The word "grains" describes their look, not their nature. Kefir grains have nothing to do with cereals, legumes or seeds. They're soft, rubbery clusters of bacteria and yeasts held together by a gel they make themselves, and they look a lot like tiny cauliflower florets.

Origins

Kefir's story begins on the northern slopes of the Caucasus Mountains, possibly in northern Ossetia, more than a millennium ago. The mountain communities of the region had a reputation for robust health and long lives. Kefir was known there as the drink of the Prophet, and the grains as the grains of the Prophet Mohammed.

The traditional method was continuous. Raw cow's or goat's milk was poured into a goatskin bag with the grains and left for about a day. To serve, the grains were pushed into a corner of the bag by hand while the kefir was poured off; then the bag was refilled with fresh milk and the cycle began again. Straining was rough, so small pieces of grain often slipped out into the cup and were swallowed along with the kefir.

Larger quantities of kefir were ripened for longer in sealed wooden barrels or clay crocks. Sometimes crushed root of the Caucasian snow rose (Rhododendron caucasicum), a plant traditionally used in the region, was added. This slow second fermentation produced a foaming drink with up to about 2% alcohol and allowed milk to be kept for long periods without refrigeration.

Because the grains grow in milk, the surplus was regularly removed to stop the bag becoming overcrowded. Spare grains were eaten, air-dried as a backup culture, or traded for other goods.

Back to contents

2

Inside the grain

Kefir grains are a community: dozens of species of bacteria and yeasts living together in a gel matrix they build themselves.

Milk kefir grains are the only known self-perpetuating natural starter for kefir. They're soft, pearly white and gelatinous, and they contain three broad groups of microbes:

• Lactic acid bacteria, which turn lactose into lactic acid and give kefir its tang.
• Acetic acid bacteria (Acetobacter), which produce small amounts of acetic acid, the acid in vinegar.
• Yeasts, some of which can break down lactose or use lactate for energy, and which provide the fizz and the trace of alcohol.

These organisms live in symbiosis, each creating conditions that suit the others. The grain's lobed body has a large surface area, and as it grows, lobes tear away to become new grains that continue the cycle. Remarkably, we still don't know how kefir grains first came about, and the biology of how they form is only partly understood. Nobody has managed to create a kefir grain from scratch using laboratory cultures. New grains only ever come from existing ones.

What a grain is made of

A Russian analysis of dried kefir grains (Dmitrichenko, 1974) found roughly the following composition:

Under the microscope, curved lactic acid bacteria with few yeasts are found encapsulated inside the grain, while other bacteria and larger yeast populations live on its surface.

Kefiran, the grain's glue

Kefiran is a water-soluble gel made mainly by encapsulated bacteria such as Lactobacillus kefiranofaciens. It's built from roughly equal parts glucose and galactose, the two sugars that make up lactose, and it binds everything in the grain into a stable, living mass. Some kefiran also passes into the milk, giving kefir its smooth, creamy body. The slippery slime you feel on healthy grains is kefiran, not a sign of spoilage.

Kefiran's structure is a branched repeating chain of sugars joined by several different kinds of link (see the Glossary for a diagram). That variety makes it hard for enzymes to break down, so it stays stable through fermentation and holds its gel strength even at boiling point. It's been studied as a natural thickener for foods such as ice cream and jam, and it's the subject of a good deal of laboratory research, summarised in Chapter 5.

Back to contents

3

From the Caucasus to the world

For centuries the grains were a closely guarded family treasure. How they finally reached Moscow is one of the great stories of food history.

Among the mountain communities of the Caucasus, kefir grains were regarded as family and tribal wealth, handed down from one generation to the next. The grains and the know-how to use them were closely guarded. One belief held that if the grains of the Prophet were shared with outsiders, they would lose their potency.

That word, potency, is worth pausing on. It suggests that people were aware of kefir's value long before scientists took an interest. In the early twentieth century, the Russian-born scientist Élie Metchnikoff, who shared the 1908 Nobel Prize in Physiology or Medicine for his work on immunity, popularised the idea that soured milks might contribute to health and long life. His work helped spark scientific interest in cultured milks, including kefir.

The story of Irina Sakharova

The tale of how kefir reached Russia has been retold so often that it's hard to separate fact from legend, but it goes something like this.

In the early 1900s, the All-Russian Physicians' Society wanted to obtain kefir grains. It approached two brothers named Blandov, who owned cheese factories in the northern Caucasus. The brothers knew of a local prince, Bek-Mirza Barchorov, who kept the grains, and they sent a young employee, Irina Sakharova, to persuade him to part with some.

The prince was charmed by Irina but refused to give up his grains. When she set off for home, he had her abducted and brought back to his court, where he asked her to marry him. She refused. The Blandov brothers rescued her and helped her bring a case against the prince before the Tsar's court. Offered gold and jewels in compensation, Irina asked instead for kefir grains, and was given them.

In 1908, so the story goes, Irina brought the first kefir to Moscow, where it was soon being used in hospitals and sanatoriums. From there kefir grains spread through Russia and beyond. In 1973, at the age of 85, Irina is said to have received a letter from the Soviet Minister of the Food Industry thanking her for her role in bringing kefir to the people of the Soviet Union.

A gift from above

In the late 1970s, while researching cultured foods, Dominic came across an account of scientists who had repeatedly failed to grow kefir grains from pure laboratory cultures. Puzzled, they asked how the people of the Caucasus had come by the grains. The answer they were given was that the grains were a gift from God, received more than a thousand years earlier.

Dominic has long been struck by a parallel with manna, the mysterious white food described in Exodus 16, whose name means "what is it?" Given how little we still understand about where kefir grains came from and how they form, it's a fitting comparison.

Back to contents

4

Grains or powdered starters?

You can make a kefir-style drink with a freeze-dried starter, but only grains give you traditional kefir, indefinitely.

Traditional kefir can only be made with kefir grains. They offer a simple, inexpensive way to make kefir continuously, and with reasonable care they can last indefinitely. There's never a need to buy a new starter.

Commercial kefir starters are sachets of freeze-dried microbes grown under laboratory conditions. They're convenient, but they're different in a few important ways.

Why can't science simply copy the grain? Mainly because the symbiosis among its organisms is still poorly understood. A grain's community organises itself, keeping its balance from batch to batch in a way that blended laboratory strains don't.

Bacteriophage and the grain advantage

Phage are viruses that infect bacteria. When a phage infects a starter bacterium, it turns the cell into a factory for new viruses; the cell bursts and releases them, and they go on to infect more cells in a chain reaction. In dairy plants, phage outbreaks can cause single-strain starters to stall within hours. Kefir grains appear to be far less vulnerable, possibly because many of their bacteria are encapsulated in kefiran and because the community is so diverse, though this hasn't been studied in depth.

What to do with the surplus

Because grains grow, you'll regularly have more than you need. Some options:

• Share them with family and friends. This is how kefir has always travelled.
• Freeze or dry a portion as a backup culture (Chapter 15).
• Use them to make water kefir, brines, cheeses and condiments (Part four).
• Eat them. In the Caucasian tradition, spare grains were eaten, and many people blend a spoonful into smoothies.

Back to contents

5

Kefir and health: what the research says

Kefir has been studied for decades. Some findings in people are well supported; many more are early results from laboratory and animal studies. Here's how they stack up.

It helps to know what kind of study you're reading about. Laboratory (in vitro) studies test kefir or its components on cells in a dish. Animal studies, usually in mice or rats, show what happens in a living body but don't always translate to people. Human trials are the strongest evidence, and for kefir there are still relatively few. Reviews of the kefir research generally conclude that the results are promising but that larger, well-designed human trials are needed.

What's reasonably well established

Kefir is a nutritious dairy food

Milk kefir keeps most of the nutrition of the milk it's made from, including protein, calcium, phosphorus, riboflavin (vitamin B2) and vitamin B12. A typical analysis is in Appendix B.

Fermentation changes the milk

Kefir microbes consume part of the lactose and produce B vitamins during fermentation and storage. In one Polish study, folate (vitamin B9) in grain-made kefir rose to more than double the level of the original milk after two days of cold storage, a bigger increase than in kefir made with a commercial starter (Drewek and Czarnocka-Roczniakowa, 1986). In a laboratory study, kefir grains removed a substantial share of the cholesterol from the milk they fermented (Vujičić and colleagues, 1992).

Lactose digestion

Kefir contains live microbes that produce lactase, the enzyme that breaks down lactose. In a small controlled trial in adults with lactose maldigestion, kefir reduced breath hydrogen and flatulence compared with milk (Hertzler and Clancy, 2003). Many people who are sensitive to milk find kefir easier to digest, though tolerance varies.

Kefir is a source of live microbes

Freshly made kefir contains very large numbers of live bacteria and yeasts (around 100 million lactic acid bacteria per millilitre in one study), and grain-made kefir contains a far wider range of species than most cultured milks.

Promising early research

The following findings are from laboratory and animal studies. They're why researchers remain interested in kefir, but they don't show that kefir prevents or treats any disease in people.

• Inflammation. In rats with experimentally induced inflammation, kefir grain preparations reduced swelling compared with controls (Diniz and colleagues, 2003; Schneedorf and Anfiteatro, 2004).
• Immune activity and tumour growth. In a series of Japanese studies, mice fed kefiran or kefir grain polysaccharide showed changes in immune response and slower growth of implanted tumours (Shiomi, Murofushi, Kubo and colleagues, 1982 to 1992).
• Cell studies. Kefir extracts slowed the growth of human breast cancer cells in a dish without affecting normal breast cells (Chen and colleagues, 2007).
• Blood pressure, blood glucose and lipids. In hypertensive rats, kefiran was associated with lower blood pressure, blood glucose and cholesterol, and with softer stools (Maeda and colleagues, 2004).
• Antioxidant activity. Milk kefir and soymilk kefir showed antioxidant and antimutagenic activity in laboratory tests (Liu and colleagues, 2005).
• Interferon. A lipid from fermented milk called sphingomyelin increased production of interferon-beta, a natural antiviral messenger, in cultured human cells (Osada and colleagues, 1993).

Getting started gently

Some people notice wind, bloating or mild stomach discomfort when they first add kefir to their diet. If that happens, start small: try ¼ cup of kefir diluted in a cup of water or fruit juice, and increase by about ¼ cup every two or three days until you're comfortable with a cupful. Kefir taken with a pinch of ground fennel, caraway, dill or cumin seed, or a cup of mint or fennel tea, can make the transition easier. If symptoms are severe or don't settle, stop and see your doctor.

Back to contents

6

Your first batch

Makes about 2 cups. Hands-on time: five minutes a day.

Choosing milk

Milk kefir grains will ferment almost any dairy milk: full cream, reduced fat or skim; cow's, goat's or sheep's; homogenised or not; straight from the fridge. Reconstituted milk powder and UHT milk both work, though they may give a thinner kefir. Whatever you use, make sure it's fresh and within its use-by date.

As your grains grow

Your grains will gradually increase, and you can increase the milk to match. With 2 Tbs of grains you can also simply use 3 to 4 cups of milk and wait until the kefir is as sour as you like. The first few batches may take 3 to 4 days at that ratio, but the time shortens as the grains grow and become more active. Ratios, timing and temperature are covered in detail in the next chapter.

Drink now or ripen first

Kefir is ready to drink as soon as it's strained, but Dominic recommends letting it ripen for a further one to two days, either in the fridge or in a partly sealed bottle at room temperature. Ripening deepens the flavour, lowers lactose further, and increases some B vitamins including folate. It also increases alcohol slightly. Chapter 8 explains how.

Back to contents

7

Ratios, timing and temperature

The three dials you can turn to make kefir thicker, milder, sourer or fizzier.

How much milk to grains?

Kefir can be made with anything from 1 part grains to 3 parts milk, up to 1 part grains to 60 parts milk, by volume or weight. As a rough guide, use about 1:7 in cool weather and up to 1:20 in warm weather. Half a cup of grains in 5 cups of milk is a ratio of 1:10.

How long to ferment

Between 15°C and 25°C, milk kefir is usually ready to strain in about 24 hours. If the milk hasn't thickened right through and tastes only slightly sour, stir it and leave it longer. It's ready when it tastes right to you. For the creamiest result, strain soon after it thickens.

When kefir separates

At around 24 hours you may see small pockets of whey through the kefir. At 36 to 48 hours a thick white curd often floats on a layer of clear, pale yellow whey. This isn't a problem; it simply means the kefir is very sour, which not everyone enjoys. Stir well before straining, since the grains will be trapped in the curd.

Separation is caused by fermenting for too long, warm weather, too little milk for the amount of grains, or a burst of activity in the grains. If it happens before 24 hours, halve the grains or use 50 to 100% more milk.

If separation keeps happening even when you adjust, Dominic suggests resetting the culture: make three batches in a row, letting each ferment for 3 to 4 days before straining. Don't worry about the taste of these batches. Normal one-day batches after the reset should be smoother.

What temperature?

The ideal temperature for both kefir and grain growth is about 22°C. Held there consistently, grains give a stable kefir with the best flavour and texture. In practice, most people simply culture at room temperature: kefir sets more slowly in cool weather and faster in warm.

• Milk kefir will ferment between about 4°C and 28°C, but grains won't grow below about 8°C.
• In cold weather (below 15°C), find a warmer spot in the house or use a low-wattage brewing heat pad. You can also warm cold milk to body temperature (no higher than 37°C) before adding the grains, then let it cool naturally.
• In hot weather (above 28°C), keep the jar in the fridge during the day and bring it out in the evening so it sets overnight. Or use an esky with ice bricks, or wrap the jar in a wet towel standing in a bowl of water, ideally in front of a fan.

Why kefir is so smooth

Kefir forms a much finer, softer curd than yoghurt. You can see it in the delicate patterns kefir leaves on the side of a glass. This fine curd is one reason many people find kefir light and easy to drink.

Back to contents

8

Ripening and storing kefir

A day or two of rest after straining changes kefir's flavour, fizz and nutrition.

In the fridge

Strained kefir keeps well in a sealed bottle in the fridge for up to a month. In one Spanish study, lactic acid bacteria fell by about 1.5 log units (roughly 30-fold) between days 7 and 14 and then stayed steady to day 28, while yeast and acetic acid bacteria numbers stayed stable throughout (Irigoyen and colleagues, 2005; see Appendix B).

Kefir gets sourer in the fridge. If you find it too tart, sweeten it with honey, maple syrup or fruit, or blend it into a smoothie. Very sour kefir is perfect for the Parmesan-style cheese in Chapter 13.

At room temperature

The people of the Caucasus kept kefir at room temperature for long periods, and a short room-temperature ripening is how many fermenters develop a richer, fizzier kefir.

1. Fill a clean bottle no more than two-thirds full with freshly strained kefir and close the lid.
2. Leave at room temperature (18 to 25°C) for 1 to 2 days, then refrigerate.
3. Shake the bottle at least once a day.

Kefir ripened at room temperature is usually less sour than kefir kept in the fridge for the same time, and its lactose falls further. Alcohol also rises with time: kefir ripened at room temperature for a week or more can reach around 2% alcohol by volume.

Flowers of kefir

If ripening kefir is left unshaken, a thin white to light-brown film can form on its surface. Dominic calls this "flowers of kefir", after the "flowers of wine" that winemakers know. It's a colony of mostly yeasts that grows where kefir meets air, and it's a normal part of kefir's flora. Shaking the bottle daily prevents it.

Don't confuse it with mould. Fuzzy, raised growth, or patches that are green, blue, black, pink or orange, mean the kefir should be thrown away.

Ripening under an airlock

For the best room-temperature ripening, use an airlock, the simple water-filled valve used by home brewers. It fits through a bung or stopper in the neck of the bottle, lets gas escape and keeps air out. Kefir ripened this way doesn't form flowers of kefir and doesn't need shaking. Airlocks and bungs are sold by home-brew suppliers.

Back to contents

9

Milk kefir questions answered

The questions Dominic has been asked most often over decades of culturing and corresponding.

Back to contents

10

About water kefir

Also called kefir d'acqua, tibicos or, historically, the ginger beer plant.

Water kefir is a refreshing, naturally fizzy dairy-free drink made with a different culture: water kefir grains, also called sugary kefir grains. They're translucent, firm, crystal-like granules that break apart easily under pressure.

Where milk grains are held together by kefiran, made of glucose and galactose, water kefir grains are made of a dextran built only from glucose. Their microbes split table sugar (sucrose) into glucose and fructose and use the glucose to build new grain.

From the sources Dominic has found, water kefir grains seem to have reached Britain with soldiers returning from the Crimean War in the 1850s, where they became known as the ginger beer plant. It's possible that they were the original culture behind traditional ginger beer, and certainly they still make an excellent one.

Water kefir with milk grains

In 1980, with no water kefir grains to hand, Dominic discovered that milk kefir grains placed in a 5% sugar solution with a slice of lemon and a dried fig would brew a very good water kefir in two days. Milk grains don't grow in sugar water, because they can't make kefiran without lactose, but the bacteria and yeasts living on them carry on fermenting batch after batch.

Once milk grains have been moved to sugar water (or used for kefirkraut), keep them there. Moving them back to milk tends to give a bitter, off-tasting kefir.

Grain growth and alcohol

Dominic noticed a pattern. With a 5% sugar solution, growing water kefir grains produced about 0.5% alcohol after 2 days, while parallel batches made with milk grains, or with water kefir grains that had stopped growing, produced about 1.9%.

Healthy water kefir grains can double their weight in 2 days with a good recipe. Some of the best growers float, buoyed by a bubble of carbon dioxide trapped inside, then sink when it escapes. This bobbing up and down earned them the nickname "California bees". Not all grains do this, and that's perfectly normal.

Is milk or water kefir better?

They're different foods, each with its own character. Milk kefir offers the nutrition of milk along with a broader microbial community; water kefir is dairy-free and suits people who avoid dairy. Dominic enjoys both.

Back to contents

11

Making water kefir

Makes about 7 cups. Brews in 2 days.

The molasses, bicarbonate and eggshell provide minerals that encourage strong grain growth. Limestone or oceanic coral can replace the eggshell; boil them for 3 minutes before first use.

If you're starting with milk kefir grains, the first batch may take up to 5 days; later batches take about 2. Water kefir grains give the best results.

Other ways to brew

Many variations work: dried apricots, prunes or sultanas in place of figs; fresh sugar cane juice diluted 50:50 with water; or young coconut water. Grape juice diluted with water makes what Dominic calls kefir d'uva, and most fresh fruit juices can be used the same way.

Water kefir tips

• Don't over-brew. Two days is usually right; most growth happens after the first 18 hours. Water kefir grains are less hardy than milk grains and can stop growing if they're regularly over-fermented.
• Rinse only slow growers. If your grains grow less than 50% per batch, rinse them under cold tap water after each strain. Grains that grow well don't need it.
• Boost growth with kefiraride. Adding ½ cup of boiled and cooled kefiraride (the soaking water from milk grains, see Chapter 9) to a 6-cup batch has, in Dominic's experience, roughly doubled grain growth.
• Short breaks. Water kefir grains can rest in a 5 to 10% sugar solution in the fridge for up to a week, but then need to go back to room temperature.

Dominic's best growth figures, up to 200% in 48 hours, came from this recipe: 150 g water kefir grains, 3 Tbs ginger juice, ⅓ cup dried sugar cane juice (rapadura), ¼ tsp bicarbonate of soda, 1 cup kefiraride and 5 cups water, with a piece of boiled coral, limestone or half an eggshell.

Back to contents

12

Drinks and smoothies

Kefir can stand in for yoghurt, buttermilk or sour cream in almost any recipe. These are a good place to start.

Herbal kefir smoothies

Kefir pairs beautifully with fresh garden herbs as well as fruit. Blend a small handful of herbs such as mint, parsley, coriander, dandelion leaf or young plantain leaf into a cup of kefir, sweeten to taste, and drink straight away. For a deeper flavour, Dominic blends the herbs with kefir and a spoonful of spare grains, then lets the mixture ripen in the fridge for a few days.

Dominic calls these herbal brews kefir d'erba medica. Some herbs have strong effects and can interact with medicines, so stick to familiar culinary herbs unless you've checked with a qualified health professional.

More drinks

Whey kefir. The sweet whey left from making cottage-style cheese (Chapter 13) can be strained, cooled and cultured with milk kefir grains for a day to make a light, refreshing drink.

Kefir with bee pollen. Stir a teaspoon of bee pollen into milk or water kefir and let it stand for a few hours. Dominic calls this kefir d'pollin. Avoid it if you're allergic to pollen or bee products.

Kefirlac. A sprouted-grain drink fermented with kefir grains or water kefir, similar to the Russian rye drink kvass.

Back to contents

13

Kefir cheeses

From a simple fresh curd to waxed, matured rounds, kefir lends itself wonderfully to cheesemaking.

Pressed and matured kefir cheeses

Kefir leban or kefir cottage-style cheese can be pressed, dried and waxed to make firmer, matured cheeses. Dominic has developed many varieties this way, from mild cheddar styles to blue and brie styles.

To press a cake of cheese

A Chinese bamboo steamer makes an excellent cheese form. Line it with dampened cheesecloth, fill with curd, smooth the top and fold the cloth over. Place a snug-fitting wooden disc (a follower) on top and another underneath to strengthen the base. Stand an 8-litre bucket of water on the follower and press for a day.

To dry and mature

Unwrap the cheese and set it on a wooden board. Each day, wipe the surface with a clean white cloth dipped in olive oil, salt brine or diluted vinegar to discourage mould, and turn it. When it has formed a thick yellow rind, dip it in melted cheese wax or beeswax to seal it. Mature in the fridge or a cool cellar for several weeks to months.

For a simpler round, hang kefir leban in its cloth for 5 to 7 days, then dry it on a board until a rind forms, and wax and mature it in the same way.

Back to contents

14

Cultured foods, baking and more

Kefir, kefir whey and kefiraride can culture vegetables, leaven bread, and even feed your garden.

Kefir sour cream and butter

Sour cream. Stir 2 Tbs of kefir into each cup of fresh cream. Cover and leave at room temperature for a day, then refrigerate in a sealed jar. The result is rich and tangy, like Russian smetana.

Cultured butter. Blend 2 Tbs of kefir grains with ½ cup of kefir until smooth, then fold into 4 cups of cream. Cover and leave at room temperature for a day, then churn into butter in the usual way. Cultured butter has a fuller flavour than sweet-cream butter.

Baking and soaking

Kefir, water kefir and kefir whey can replace some or all of the liquid in breads, pizza bases, cakes, scones, pancakes and pastries. With baking powder or self-raising flour, swapping in a little kefir gives a lighter result. Kefiraride can replace up to half the liquid in a recipe, and kefir whey up to a quarter.

Kefir can also act as a natural leaven, like a sourdough starter. Make your dough with kefir, put it in the tin, and leave it somewhere warm until it has doubled in size before baking. Expect a slower rise than with commercial yeast.

For a softer, tangier breakfast, soak rolled oats or other cereals overnight in a 50:50 mix of milk kefir and water, or in water kefir, then cook as usual. Soaking in an acidic liquid is also a traditional way to reduce phytates, compounds in grains that can reduce mineral absorption.

Kefirkraut

Adding spare milk or water kefir grains to shredded cabbage and other vegetables gives sauerkraut and pickles a lively, reliable start, and lets you use little or no salt. Use fresh spare grains for each batch, and don't return them to milk afterwards; the cabbage flavour taints the grains.

Kefir preserving brine

Dominic developed this tangy, aromatic brine to culture and flavour vegetables, tofu, tempeh and fresh cheeses such as bocconcini, ricotta and cottage cheese. The microbes in the brine ferment the food's natural sugars into lactic acid, carbon dioxide and a little acetic acid, giving a mildly sour, pickled flavour.

In Dominic's experience, renewing the brine every two weeks keeps produce in good condition for weeks or months. Treat long storage as an experiment: keep the container in the fridge below 5°C, keep the food fully submerged, and discard anything that becomes slimy, mouldy or smells unpleasant.

Kefir grain condiments and sweets

Savoury herbal sprinkle. Grind 1 Tbs each of dried milk or water kefir grains, sea salt, mixed seed spices (fennel, anise, dill or caraway) and toasted unhulled sesame seeds. Sprinkle over warm food just before eating.

Sweet sprinkle. Mix finely ground dried kefir grains with malt powder and sprinkle over porridge or fruit, or stir into kefir.

Lolloz. Knead dried kefir grain powder with rice malt syrup until it holds together, shape into small balls, and dip in melted dark chocolate.

Kefir gelato. Blend kefir grains or water kefir grains with cream and honey or fresh fruit purée, and churn in an ice-cream machine, or in a stainless steel bowl spun in a larger bowl of salted ice.

In the garden

Spare kefir whey makes a useful liquid fertiliser. Collect it in a large bucket with eggshells and a few handfuls of wood ash, cover with a heavy cloth to keep out insects, and stir regularly. After about 2 months, dilute with water and pour over mulched vegetables and trees. It will smell strongly; a few handfuls of charcoal help, and the spent charcoal can be dug into the soil.

Back to contents

15

Storing, reviving and rescuing grains

A backup of your grains costs nothing and can save a culture you've kept for years.

Freezing grains

Freezing keeps grains for about 2 months, and some people have had success after 6 months.

1. Strain the grains from a fresh batch and rinse them in cold, non-chlorinated water.
2. Pat them dry between clean towels or paper towels.
3. Put them in a zip-lock bag or jar and cover with full-cream milk powder (for water kefir grains, use dry malt extract). This protects them from freezer burn.
4. Seal, mix well and freeze.

Alternatively, culture milk grains in 3 parts milk for 12 to 18 hours, then freeze the whole lot, grains and kefir together, in a strong zip-lock bag.

Drying grains

For long-term storage, drying is best.

1. Strain, rinse in fresh non-chlorinated water and pat dry, as above.
2. Spread the grains in a single layer on a clean lint-free towel or stretched nylon fabric and cover with another layer of thin fabric to keep off dust and insects. A wooden frame with nylon curtain fabric stapled over it works well.
3. Leave in a warm, airy spot until the grains are brittle and hard. This takes 1 to 4 days depending on temperature, humidity and grain size.
4. Put the dry grains in a paper bag inside an airtight glass jar with a sachet of silica gel. Store in a cool, dry place or the fridge. Don't freeze dried grains.

Dried milk kefir grains should stay viable for about 2 years at around 4°C; dried water kefir grains for about a year. To be sure you always have a live backup, replace your dried grains with a fresh batch every 6 months.

Reviving frozen grains

Thaw the grains in a bowl of fresh water for 15 minutes. Strain, and rinse milk grains under cold water to remove the milk powder. Put them in a clean jar with 3 to 5 parts fresh milk, cover, and leave at room temperature for 24 hours. Strain and repeat daily. Water kefir grains just need rinsing before being used as usual.

Your grains are revived when the milk sours within 24 hours and the kefir tastes and smells clean, sour and lightly yeasty. Discard batches until then; this may take anything from a few days to a week. After that, add an extra ¼ cup of milk every third batch until you're making as much as you need.

Reviving dried milk grains

1. Soak 1 to 2 Tbs dried grains in ½ cup fresh water for 2 hours.
2. Stir in ½ tsp bicarbonate of soda and leave for another 2 hours.
3. Strain, rinse in body-temperature water, and put the grains in a clean jar with ½ cup fresh milk. Cover.
4. Strain and replace the milk every 24 hours.
5. Don't drink the kefir until it smells appealing and tastes cleanly sour at 24 hours. Then add about ¼ cup more milk every third batch.

The bicarbonate soak is Dominic's own technique. It helps prevent the bitter, musty taste and foaming that can occur in the first weeks of reviving dried grains. Without it, some froth in the first week or two is normal; it settles as the bacteria and yeasts rebalance.

Revived grains usually sit at the bottom of the jar at first. As they recover they turn pearly white and feel slimy inside when squeezed, which means growth has started. That usually takes 2 to 4 weeks, but can take up to 12 if only a small part of the culture survived storage. Be patient and keep up the daily milk changes.

Rescuing damaged grains

Grains left in the same milk for too long, at room temperature or in the fridge, can develop a crust of yellowish, granular material on the surface. Encrusted grains grow slowly or not at all, and if the crust isn't removed they eventually stop growing for good. The same treatment helps grains that won't start growing within 2 weeks of being revived.

Damage starts at the surface and works inwards, so grains that look hopeless can often be saved.

1. Wash your hands well. Half-fill a bowl with boiled water cooled to body temperature.
2. Submerge a fine sieve in the water and put the grains in it.
3. With clean fingers, roll the grains firmly against the mesh. Damaged surface material will rub off and pass through; healthy grains release slime and stay in the sieve. Don't worry if grains break into smaller pieces.
4. Discard any grains that turn to mush, like squeezed cheddar.
5. Use the cleaned grains to make kefir in the usual way.

A bone-white cloudiness in the water as you work, with whiter grain revealed underneath, is a good sign: there's healthy grain under the crust.

If you suspect contamination

If grains produce kefir with an off smell or taste, clean them as above, then cover them with a commercial plain kefir, yoghurt or buttermilk containing live cultures. Seal and leave for 12 hours at room temperature, then add your usual milk and culture for a day. Repeat with the commercial culture for 3 more batches, then return to normal.

Back to contents

A

Microbes of kefir grains

Species reported in milk and water kefir grains from around the world. No single grain contains all of them.

Milk kefir grains

† aroma-forming. ‡ can use lactose or lactate. * reported to produce vitamin K2. Where two yeast names are given, the first is the sexual (teleomorph) form and the second the asexual (anamorph) form. Names are given as published in the source literature; several lactobacilli were reclassified in 2020 (for example, Lb. kefiri is now Lentilactobacillus kefiri and Lb. plantarum is now Lactiplantibacillus plantarum).

Water kefir grains

Sources: milk kefir grains, compiled from Macrae and colleagues (1993), Angulo and colleagues (1993), Koroleva (1988), Rehm and Lehner (1990), Simova and colleagues (2002), Loretan and colleagues (2003), Latorre-García and colleagues (2007) and Lopitz-Otsoa and colleagues (2006). Water kefir grains, Moinas and colleagues (1980).

Back to contents

B

Composition and storage data

Reference figures for the curious. Values vary with the milk, the grains and the method.

Typical composition of milk kefir

Per 100 g, kefir made from pasteurised whole cow's milk with a commercial starter. Sources: Hallé and colleagues (1994); Renner and Renner-Schaven (1986).

Notes on the composition table

• Energy and lactose. These figures are for kefir made with a commercial starter and stored for 24 hours. In grain-made kefir, some lactose is turned into kefiran that stays with the grains, and kefiran in the drink is poorly digested, so available carbohydrate may be slightly lower. Room-temperature ripening lowers it further. More research is needed.
• Organic acids. Pyruvic and hippuric acids are formed during fermentation but weren't detected during 21 days of storage at 4°C; orotic and citric acids rose slightly. Lactic acid rose during storage to a maximum of about 7,739 ppm at day 21 (Güzel-Seydim and colleagues, 2000).
• Alcohol. Fresh kefir's alcohol varies with the milk and method and rises during storage. Long room-temperature storage can take it to 2 to 3%.
• Folate. Grain-made kefir had the least folate when freshly strained but the fastest increase in storage: up 116.2% after 48 hours at 4°C (Drewek and Czarnocka-Roczniakowa, 1986).
• Aroma compounds. Acetaldehyde doubled between day 0 and day 21 of cold storage, while acetoin fell from 25 to 16 ppm; diacetyl wasn't detected (Güzel-Seydim and colleagues, 2000).
• Cholesterol. Kefir grains from different sources removed up to 62% of the milk's cholesterol after 24 hours at 20°C, and up to 84% after 48 hours at 10°C (Vujičić and colleagues, 1992).

Milk kefir during cold storage

Irigoyen and colleagues (2005) made kefir with 1% and 5% grains, strained it at 24 hours, and stored it at 4 to 6°C for up to 28 days.

Water kefir analysis

Water kefir made with 7% sugar and water kefir grains, fermented for 2 days, then stored at room temperature. Data courtesy of Christian Membrard, France, 2002.

n/r: not reported. For perspective, these methanol levels are far below those typically found in fruit wines.

Back to contents