What are milk kefir grains
Milk kefir grains are a living culture used to ferment milk into a tangy, drinkable yoghurt-like product. Milk kefir grains are soft, white, irregular clusters that resemble tiny cauliflower florets or small clouds (or, as my youngest son says, they look like tiny brains). They are not related to cereal grains despite the name.
They grow and reproduce over time when kept in the right conditions and can be maintained indefinitely with regular feeding. Being a mesophilic culture, they can ferment at room temperature and do not require heaters or incubators.
Milk kefir grains are one of the easiest live cultures to maintain at home once you understand how to grow and feed them correctly. I have been keeping kefir grains in my home kitchen for a number of years, and they are one of the more reliable and low-maintenance live cultures once established.
Fermenting kefir at home using heirloom grains is generally far cheaper than buying it from a supermarket. Once established and properly maintained, kefir grains can be kept going for many years and regularly propagated.
Kefir made from live grains typically contains a wider diversity of microorganisms than most commercially produced kefir products or powdered starter cultures.
The following methods are based on my own long-term use of kefir grains in a home kitchen setting.
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| Milk kefir grains after straining, ready for a fresh batch of milk |
What you need
To get started making kefir at home, you only need a few basic items:
- Milk kefir grains
- Fresh milk (cow, goat, or sheep milk all work)
- A glass jar
- A breathable cover (cloth or loose lid)
- A plastic or wooden spoon
- A strainer
A note on equipment
Some of the equipment mentioned in this post may include Amazon affiliate links. If you purchase through these links, I may earn a small commission at no extra cost to you.
Glass jars (fermentation base)
Many people (including myself) simply reuse glass jars that originally contained pickles or jam.
Fermentation jars designed for home culturing can make the process more consistent, especially if you plan to keep kefir long term. Fermentation jars also tend to look a lot nicer than using an old pickle jar like I do, and avoid any risk of residual flavours from previous contents.
A standard wide-mouth jar is usually sufficient, but thicker glass fermentation jars are more durable if you plan to keep kefir going over the long term.
- Ball Wide Mouth Mason Jars (16oz or 32oz) - commonly used for kefir and other ferments
- Kilner Glass Fermentation Jars - heavier duty option with a more traditional fermentation design
Straining equipment
Straining is the step that most people underestimate. A good strainer makes a noticeable difference.
- OXO Good Grips Stainless Steel Fine Mesh Strainer (3-inch or 4-inch) - very commonly used for kefir and other small-batch fermenting
- Bellemain Stainless Steel Fine Mesh Strainer Set - useful if you want multiple sizes for different batches
- Plastic fine mesh strainer set - useful as it has multiple sizes and good if you do not want to use metal around your kefir grains
Plastic strainers work, but stainless steel tends to last far longer and can be easier to clean.
Optional starter kits (everything-in-one setup)
If you prefer starting with a complete set rather than collecting items individually:
- Kilner Glass Kefir Jar Set - purpose built system with strainer lid and beechwood measuring spoon
- Kefir Starter Kit (various Amazon listings) - usually includes fermentation jar, strainer, sometimes grains
These are not essential, but they can make the first few batches more consistent and provide confidence if you are new to fermentation.
Important: when starting out, do not use 'starter culture' or any dried kefir culture, these don't work the same. When starting out making kefir at home, you need to use kefir grains. These are the easiest for a beginner to use, with the lowest chance of anything going wrong (which is important when dealing with food), they can live indefinitely, and usually contain significantly greater diversity of probiotic and other beneficial microorganisms and generally boast a higher number of colony forming units.
Grain quantity affects how quickly kefir ferments. For a more detailed discussion, see my article on how much milk kefir grain to use.
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| Milk kefir grains, most use between 1 teaspoon to 1/4 cup per cup of milk |
Basic method - how to make milk kefir at home
- Place the kefir grains into a clean glass jar
- Add fresh milk (roughly 1 cup of milk per 1–16 teaspoons of grains)
- Cover the jar with a cloth or loose lid
- Leave at room temperature (around 18–25°C is ideal)
- Allow to ferment for 24–48 hours depending on temperature
- When the milk thickens and smells slightly sour, it is ready
- Strain the grains out and transfer them to fresh milk
The finished kefir can be consumed immediately or stored in the fridge.
Straining and handling the grains
One of the key steps in maintaining kefir is separating the grains from the finished liquid.
A fine strainer makes this much easier. I prefer a mesh strainer that is not too fine, otherwise the thicker kefir can block it.
Useful tools for this step:
- Fine mesh strainer (plastic or stainless steel)
- Bowl or jug for catching the finished kefir
- Funnel (optional, for bottling)
A simple strainer and jar setup is usually enough, but some people prefer dedicated fermentation kits that include everything in one set.
Ongoing care
I started making milk kefir using grains in 2010. I can confidently say that I find milk kefir simple to keep going long term, and they are one of the lowest maintenance ferments I can think of. Kefir grains do not require much maintenance, but they do best with regular feeding.
If left too long without fresh milk, they will slow down or become inactive. In normal use, they will continue to grow and divide gradually.
If you are not using them for a short period, they can be stored in the fridge in fresh milk for around 1–2 weeks.
Temperature and seasonal effects
Fermentation speed changes with temperature:
- Warm weather: 12-24 hours
- Cool weather: 24-48 hours or longer
In cooler months, I generally leave them slightly longer before straining.
Optional upgrades once you are established
Once kefir becomes part of a routine, a few extra tools can make the process easier:
- Glass bottles for secondary fermentation (slightly fizzy kefir)
- Dedicated fermentation jars with breathable lids
- Thermometer strips for consistent jar temperature monitoring - I've never used thermometer strips, nor could I change the temperature if it was wrong, but lots of beginners seem to like them
These are not necessary, but they help if you want more consistent results.
Signs your kefir is healthy
Healthy grains will usually:
- Increase slowly in size over time
- Produce consistent thickening of milk
- Develop a clean, slightly sour smell after fermentation
If the culture weakens, it is usually due to long gaps between feeds or extreme temperatures.
Kefir Grain Reproduction and Sharing
Kefir grains naturally multiply when kept in good condition. Once established, they can be split and shared or stored as backup cultures.
This makes kefir grains a long-term renewable culture when properly maintained.
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| Homemade milk kefir fermenting from live kefir grains |
Common mistakes when starting out
- Leaving grains too long without feeding
- Putting grains in the fridge too often (cold can make some strains go dormant)
- Using airtight lids during primary fermentation
- Overheating in summer months
Frequently Asked Questions
Can I use UHT or long-life milk or low fat milk to make kefir?
Yes, you can use UHT milk or low fat, but the results can be slightly different. Fresh milk generally produces thicker, more consistent kefir. UHT milk tends to work, but the grains may take a few batches to adjust if they are used to fresh milk. Low fat milk usually works, but will taste a little different.
How long do milk kefir grains last?
Milk kefir grains can last indefinitely if they are cared for properly. As long as they are regularly fed with fresh milk and kept at reasonable temperatures, they will continue to grow and reproduce over time.
Why is my kefir separating into layers?
This is usually normal. Separation into a thicker curd layer and a watery whey layer generally means the kefir has fermented for too long or the temperature is a bit warm. It is still safe to use. You can simply stir it back together or shorten the fermentation time next batch.
Can kefir grains die?
Yes, but it usually takes extreme conditions as kefir grains are quite resilient and have been used for a long time in traditional fermentation. Kefir grains can weaken or die if they are:
- left without fresh milk for too long
- exposed to very high temperatures
- repeatedly contaminated or neglected over time
In most normal home situations, they are quite resilient and can recover even after periods of stress.
How much milk should I use per batch?
A common starting ratio is about 1 cup of milk per 1 to 16 teaspoons of kefir grains. I tend to use far more grains than this. You can adjust this depending on how fast you want fermentation to occur. More grains = faster fermentation.
Can I use metal utensils with kefir grains?
Yes, brief contact with stainless steel is generally fine. Avoid fermenting kefir in reactive metals (like aluminium or copper), as acidity can affect them. Stainless steel is generally safe for short contact (such as straining) but not ideal for long fermentation. Most modern kefir keepers use stainless steel strainers without issues. However, many people still prefer plastic or wooden utensils for routine handling.
Why do my kefir grains look smaller or not growing?
Grain size can fluctuate seasonally depending on milk type, temperature, and feeding schedule. Growth is usually slow and not always obvious day to day. If fermentation is still happening normally, the grains are usually fine.
How do I store kefir grains if I need a break?
If you are not making kefir for a short period, you can store the grains in fresh milk in the fridge for a week or two. For longer breaks, the milk should be changed occasionally to keep them healthy. If they are in the fridge for a long time, it may take them a while to wake up and work normally again.
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| Milk kefir grains - look like little clouds |
Is homemade milk kefir stronger than store-bought kefir?
Homemade kefir made from live grains typically contains a wider range of microorganisms compared to most commercial kefir or powdered starter cultures. The strength and flavour also vary depending on fermentation time and conditions, which you have greater control over when fermenting at home.
Notes from growing milk kefir grains at home
In my experience, milk kefir grains are one of the most reliable live cultures for home use. They tend to adapt well over time and can recover even after periods of neglect, provided they are returned to fresh milk.
Both the temperature, and the amount of grain used affects how quickly kefir ferments. For a more detailed discussion, see my article on how much milk kefir grain I tend to use.
Kefir Grain Availability
Milk kefir grains are available from time to time as part of my live cultures listing, usually in small starter portions suitable for home propagation. Many suppliers sell very small starter portions, often around 1 teaspoon. While these can work, I find beginners usually have more success starting with a larger quantity of healthy grains. I include a decent amount of grains, closer to 1/4 cup of grains (or 16 teaspoons) that way the beginner is far more likely to succeed.
Milk kefir grains are one of the simplest and most forgiving fermentation cultures for beginners. With only milk, a jar, and a small quantity of healthy grains, you can maintain a continuous supply of homemade kefir for years. Once established, the grains multiply naturally, making kefir one of the most economical fermented foods you can produce at home.
