Milk Kefir FAQ | Grain Health, Care & Contamination

 

 

Why are My Kefir Grains not Working?

If your grains don't seem to be working right away, don't worry! This is common, especially for new kefir grains – they just need some time to adjust. Other common reasons are low temperatures, damaged grains, or using milk that isn't suitable. With a little patience, they'll usually bounce back and start making delicious kefir within a few days.

Low Temperature

Milk kefir grains like a cozy, warm environment – they best ferment in the range of approximately 18°C - 28°C (65°F - 85°F). Temperatures below this can significantly slow down fermentation.

New Environment

If you have purchased new kefir grains, especially online, it can take a few batches for your kefir grains to get settled and comfortable in their new home. It is normal for the grains not to appear to work or to make an odd-tasting milk kefir during the first batch or two. Simply keep making new batches every 24 to 48 hours and your grains should be fully active within a week.

Unsuitable Milk

Milks like UHT long-life milk, powdered milk, or lactose-free milk don't always give the best result. You can think of it like feeding your grains junk food – they will survive, but won't thrive.

Damaged Grains

If your grains have been damaged by excessive transit time (over 2 weeks), high temperatures, infrequent feedings, or contamination, such as mould, they can struggle to ferment milk. In cases of contamination, the grains should be discarded. For all other cases, there is a chance of the grains eventually recovering, but it may take a long time or never happen at all – purchasing new kefir is recommended if they don't show signs of recovery within a week.

Storage Methods

If the grains have been previously frozen or dehydrated, they can become very sluggish in activity; particularly if they have been stored for a long time or damaged by improper freezing or dehydration techniques. Recently revived grains can take 2 days to 2 weeks to fully recover if properly stored and revived, while improperly stored or revived grains may never fully recover.

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What Should Healthy Milk Kefir Grains Look Like?

Think of kefir grains as tiny cauliflowers or little squishy coral pieces. They are usually:

• White to light yellow in colour
• Gelatinous, slightly slimy, and elastic in texture
• Irregularly shaped
• Ranging in size from about 2 mm to 3 cm

With that being said, kefir grains can vary widely in appearance depending on factors such as their microbial composition, the type of milk used, straining methods, and environmental conditions. For example:

Some grains may be as small as a grain of rice – sticky and uneven in shape.
Others may grow as large as a cherry – smooth, rounded, and firm.

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Does Grain Size Matter? Are Small Grains Bad?

Small grains are not bad at all! In fact, they are like tiny superheroes. Small kefir grains tend to ferment milk faster because they have a higher surface-to-mass ratio, allowing the yeast and bacteria within to colonise and ferment more efficiently.

Encouraging grains to grow large enough to create a noticeable difference requires deliberate techniques, such as gentle straining and fermenting at around 18°C (65°F), which promotes grain growth over division.

Some people prefer larger grains for cosmetic reasons, and in some cases, they can make straining easier. Once grains are large enough, they can be scooped out with a fork instead of being strained through a sieve.

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Are Milk Kefir Grains Supposed to Float or Sink?

It is normal and healthy for kefir grains to float or sink throughout the fermentation – neither position suggests that there's anything wrong with the grains or the fermentation.

Most of the time, the grains will be floating because they trap little bubbles of CO2 and rise like tiny balloons. They can also become stuck to milk curds, which also trap CO2 and rise to the top of the jar. At the start of a fermentation, or in a mildly fermented milk kefir, its not uncommon for the grains to stay at the bottom of the jar due to a lack of CO2.

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Are My Kefir Grains Dead?

Kefir grains are tough little creatures and will rarely die. Most of the time, they will go dormant/sluggish due to low temperatures, cold storage, infrequent/missed feeds, or stress from unsuitable milk types. A little love, care, and patience will get the grains back to tip-top shape.

Healthy milk kefir grains will ferment milk easily within 24 to 48 hours, producing a sour smell, slight thickening of milk, and small bubbles. See our milk kefir grain instructions and recipes page to learn how to make tasty milk kefir while supporting grain health. If conditions don't improve after a week, consider sourcing new kefir grains.

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Why are My Kefir Grains Mushy or Disintegrating?

Milk kefir grains will become mushy and then start to disintegrate when they have become damaged. This can be due to infrequent/missed feedings, excessive heat, and stress from unsuitable milk types.

It is possible to save the kefir grains if they aren't too damaged by doing multiple fermentations under optimal conditions. See our milk kefir grain instructions and recipes page for how to make tasty milk kefir while supporting grain health. If conditions don't improve after a week, consider sourcing new kefir grains.

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Is There Mould On My Kefir Grains or Milk Kefir?

Mouldy kefir grains or milk kefir will have a fuzzy or dry-looking texture on the surface, and it can come in many colours, such as white, blue, green, pink, black, or brown. This is distinct from dried milk on the sides of the fermentation jar, milk curd, separation during fermentation, or a white film on the surface of the kefir (Kahm yeast, discussed in the question below).

Genuine mould is extremely rare in our experience – but if you do see it, you should discard the milk kefir and the grains to be safe. Don't attempt to save the grains.

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Why is There a White or Light-Brown Film on My Milk Kefir?

Kahm yeast is a harmless, yet undesired yeast that can form a white, creamy film on the top of your milk kefir. It is not dangerous to consume, but the taste and smell that it produces can be unpleasant.

Signs of Kahm Yeast

• Appearance: A thin, flat, white or cream-coloured film that forms on the surface. It looks dull, not fuzzy or brightly coloured like mould.
• Texture: It's often powdery, chalky, or paper-like.
• Smell: Kahm yeast can smell slightly yeasty, sour, or sometimes like nail polish remover (acetone-like).
• Spread: It usually covers the surface evenly, unlike mould, which grows in spots or fuzzy patches.

Removing Kahm Yeast

1. Skim it off carefully and discard the top layer.
2. Rinse the grains with fresh milk.
3. Make a new batch of milk kefir, using our instructions.
   1. Our instructions are for a closed-lid fermentation, which reduces yeast activity. compared to an open-lid/cloth fermentation.
4. Let it ferment for 24 to 48 hours, at a temperature less than 25°C (70°F).
5. Repeat until there are no signs of kahm yeast left.

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Can I Save Contaminated Or Mouldy Kefir Grains?

No, you should not try to save contaminated or mouldy milk kefir grains – it is easier and safer to acquire new kefir grains. In cases of mould, some individuals have successfully saved mouldy, forgotten kefir grains by isolating a small, unaffected piece of the mouldy batch and slowly growing more. But for time, cost, effort, and safety, it is not worth it.

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I Forgot to Feed My Kefir Grains. Are They Okay?

Don't worry, your kefir grains will be just fine! They are incredibly forgiving if you forget to feed them on occasion. Just don't make a habit of it. Make your next batch of milk kefir as normal, keeping in mind that the kefir will likely be very fermented and sour.

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Why Do My Grains Look Like Hollow Balloons or Flat Ribbons?

Your grains may sometimes look like hollow balloons or flat ribbons. This is normal! As the grains are made up of yeast and bacteria, which adapt to their conditions, the grains will change shape over time.

These grains can form when normal kefir grains (particularly large ones) are cut or pressed too firmly. Once opened, milk enters the opening, creating an interior surface in the grains. This causes the grains to grow as flat sheaths or as hollow balloons instead of self-enclosed grains.

This doesn't have a negative effect on their ability to ferment milk and doesn't indicate poor grain health. Over time, the grains will naturally form back into self-enclosed grains, or break apart with rough straining.

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Why Do My Grains Have Sticky, Thread-Like Strings When Separated?

When you separate your grains, you might see thin, sticky threads, like cheese strings on pizza. It is nothing to worry about; this is simply kefiran, a protective polysaccharide produced by the grains.

It is also normal for kefiran to not be present, as the production of kefiran is influenced by temperature changes, grain-to-milk ratio, and grain microbe composition. Studies have found that it may help modulate the immune system, lower cholesterol, and have anti-tumour properties.

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How Fast Should Kefir Grains Grow?

Milk kefir grains grow at a slow pace, especially compared to water kefir grains. Milk kefir grains will roughly double in volume every 2 weeks when kept at a temperature between 18°C - 28°C (65°F - 85°F), fed regularly with whole milk. If your grains are growing slower than this or not at all, read the section below.

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Should I Wash or Rinse My Kefir Grains?

No, you shouldn't rinse your kefir grains with milk or water after straining in most circumstances. It removes the protective biofilm from the outside of the kefir grains, increasing the risk of contamination by foreign microbes or mould, and slowing down grain growth.

This biofilm also acts as a reservoir for the microbes, helping to kick-start the next fermentation. In fact, some species of bacteria and yeast are only abundant in these biofilms, not in the grains themselves.

The only circumstances where you should wash your grains is if you're moving orange/yellow fat deposits, caused by pasteurised, non-homogenised milk (rare), or decontaminating the grains of a foreign microbe, such as kahm yeast or Viili (also rare).

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Why Do My Kefir Grains Have Orange/Yellow Patches?

This normally occurs when using pasteurised, non-homogenised milk. During fermentation, particularly in warm temperatures, the fat from the milk can become stuck on the kefir grains, giving them a yellow or orange colour/crust. This restricts the grain's access to fresh milk, slowing down the grain's productivity and growth. To remove the fat deposits, lightly rinse the grains in fresh milk and gently scrub off any deposits with clean fingers.

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Can Milk Kefir Grains Become Cross-Contaminated With Other Cultures, Such as Kombucha?

Except Viili/Fil (covered below), you shouldn't need to worry about cross-contamination with other cultures. We have had jars of sourdough starter, kombucha, water kefir, and milk kefir next to each other for years and have never seen any negative signs of contamination. While it is likely that the cultures have picked up some strains of yeast or bacteria from each other, we have seen no ill effects.

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Why is My Milk Kefir Stringy and Elastic?

Viili (Finnish) or Fil (Swedish), is a fermented milk product popular in Finland and Sweden. When contamination occurs, which can be as simple as having Villi nearby. The milk kefir produced will be stringy and elastic in consistency. Besides creating a possibly undesired texture and taste, straining and separating your grains becomes extremely difficult.

Removing Viili Contamination

1. Rinse the grains well with non-chlorinated water.
2. Make a new batch of milk kefir.
3. Let it ferment for 24 to 48 hours.
4. Repeat until there are no signs of Viili contamination left

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Why Aren't My Kefir Grains Multiplying?

Under ideal conditions, milk kefir grains typically double in volume every 2 weeks. It's normal if you don't notice visible growth from batch to batch. However, if your grains are growing much slower than this—or not at all—one or more of the following factors may be to blame. Sometimes a small adjustment is enough to get them thriving again, but in other cases, the grains may be too stressed and need to be replaced.

Ambient Temperature Too Low or High

• Kefir grains like to be cozy and warm at 23 °C (75 °F), close to room temperature.
• They can still do well between 18 °C–28 °C (65 °F–85 °F).
• Below this range, grains become sluggish; above it, they may weaken or even die.

Overcrowding

• As grains multiply, they need more milk to support their growth. Use roughly 1 teaspoon of grains per 1 cup of milk.
• Using too many grains and not enough milk can cause over-fermentation, stunting the grain's growth.

Infrequent Feedings

• Kefir grains need regular feeding to stay active. Letting milk sit for more than 2 days before refreshing can stress or harm the grains.

Type of Milk

• Grains generally grow fastest in full-cream, organic cow's milk, goat's milk, or sheep's milk. They can survive in reduced-fat milk, but growth may be slower.
• Plant-based, skim, and lactose-free milks do not support growth.

Over-Fermentation

• If kefir ferments too long, the liquid becomes overly acidic. This harsh environment can weaken or damage the grains.

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Why Does My Milk Kefir Taste/Smell Bitter?

Bitter-tasting or off-tasting milk kefir can be due to over-fermenting, using too many kefir grains, contamination, or grains under stress (adapting to a new environment, recovering from refrigeration, etc.). Most of the time, it can be solved by fixing these issues as described below.

Over-fermentation

• Signs include strong tastes and separation of milk.
• Shorten the fermentation time, discard some of the kefir grains, use more milk, and/or ferment at room temperature.

Using Too Many Kefir Grains

• Remove some of the grains until the ratio is at ~1 tsp of grains per cup of milk.

Stressed Grains

• Can be caused by a new environment, removing the milk kefir grains from cold storage, reviving them, infrequent feedings, or over-fermentation, temperature fluctuations
• Make your milk kefir as normal and give the grains a week to adapt

Contamination

• In rare instances, we have had customers implement all the above changes, and still have bitter milk kefir, indicating contamination
• The grains may rebalance themselves over multiple batches if you give the grains a light rinse and scrub with fresh milk after straining.
  
• If all else fails, new grains should be purchased

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Why Does My Milk Kefir Taste/Smell Like Rotten Eggs, Sulphur, or Yeast?

Milk kefir with a sulphury, yeasty, or off smell is common and indicates an imbalance of yeast and bacteria in the grains or contamination. Common causes can be due to not stirring your milk kefir, over-fermentation, using too many grains, stressed grains, open-lid fermentations, or high temperatures. Fixing one or multiple of these issues should reduce the dominance of yeast and increase bacterial activity.

Not-Stirring Your Milk Kefir

• Non-stirred milk kefir favours the growth of yeast over bacteria.
• Stirring once or twice every batch can make a big difference.

Over-fermentation

• Signs include strong tastes and separation of milk.
• Shorten the fermentation time, discard some of the kefir grains, use more milk, and/or ferment at room temperature.

Using Too Many Kefir Grains

• Remove some of the grains until the ratio is at ~1 tsp of grains per cup of milk.
  Grains Under Stress
• It can be caused by a new environment, removing the milk kefir grains from cold storage, reviving them, infrequent feedings, over-fermentation, and temperature fluctuations.
• Results in an imbalance of yeast to bacteria strains.
• Make your milk kefir as normal and give the grains a week to adapt.

Temperature

• High temperatures favour the growth and activity of yeast over bacteria.
• Aim to ferment at the lower end of this temperature range: 18°C - 28°C (65°F - 85°F).

Open-Lid Fermentations

• Open-lid fermentations with a cloth provides fresh oxygen to the fermentation, encouraging yeast dominance.
• Doing a closed-lid fermentation, will make the milk kefir less yeasty and more sour in taste.

Contamination

• Contamination by wild strains of other yeast or bacteria, such as kahm yeast, can produce yeasty or off-putting tastes.
• The grains may rebalance themselves over multiple batches of kefir and light rinses with fresh milk between batches.
• If all else fails, new grains should be purchased.

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Why Is My Milk Kefir Thin or Watery?

Milk kefir should naturally become thicker throughout the fermentation. If your milk kefir is thin or watery, it is likely due to one of the factors below.

Under-Fermentation

Under-fermentation means that the milk hasn't fully fermented and transformed into milk kefir. This can be due to a range of factors, such as:

• New Grains: If you have new kefir grains, they can take up to a week to adapt to their new environment and become fully potent
• Short Fermentation Time: A short fermentation time under 24 hours can result in a partially fermented milk kefir
• Low Temperature: A temperature under 18°C (65°F) can result in a partially fermented milk kefir. Increasing the temperature by placing the grains somewhere warm or extending the fermentation time to 48 hours can solve this issue.
• Low Grain-to-Milk Ratio: We recommend a ratio of at least 1 tsp of milk kefir grains to 1 cup of milk to ensure that the grains can do their job properly.

Milk Type

Full cream dairy milk will give you the thickest milk kefir due to its extra fat content. Using skim or lite milk, which contains less fat, will result in a thinner milk kefir.

Temperature

Milk kefir fermented at warmer temperatures usually turns out thinner, while cooler fermentations produce a thicker, creamier texture. This happens because higher temperatures encourage yeast activity, whereas lactic acid bacteria thrive at lower temperatures.

Since lactic acid bacteria produce the polysaccharides that give kefir body and thickness, a yeast-dominant ferment will naturally be thinner. An ideal range for fermenting milk kefir is 18°C - 28°C (65°F - 85°F). Aim for the lower end of this range for a thicker kefir.

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Why Is My Milk Kefir Lumpy and Gritty?

This happens when milk kefir has overfermented, separating into white milk curds (solid) and yellow-clear whey (liquid). This happens because highly fermented milk kefir has a low pH due to its high lactic acid content. This causes the milk protein, casein, to coagulate and separate from the liquid whey. To prevent milk kefir from becoming overfermented, you can do one or more of the following:

• Discard Some of the Kefir Grains: We recommend using about 1 teaspoon of kefir grains per cup of milk.
• Shorten the Fermentation Time: If you're fermenting for 24 to 48 hours, shorten the fermentation time to 12 or 24 hours.
• Make Larger Batches: Increase the quantity of milk added to the batch so that you can achieve a ratio of ~1 teaspoon of kefir grains to 1 cup of milk.
• Ferment in a Cooler Location: Milk kefir grains ferment best at a temperature range of 18°C - 28°C (65°F - 85°F). If you're fermenting at the upper end of this range, move your jar to a cooler location.