When readers type in “composition of milk kefir”, they’re not just looking for a definition. They want to know, in concrete terms, what’s in their glass. They want to understand whether kefir is “just fermented milk”, whether it still contains lactose, what creates the acidity, why the texture changes, and why homemade kefir is not identical from one preparation to the next.
This question is also important for a very simple reason: milk kefir is a living drink, so its composition is not fixed like that of a standardised industrial product. The composition depends on a number of factors: the type of milk, the quantity of grains, the fermentation time, the temperature, and even the state of health of the culture.
Understanding the composition therefore means understanding the general logic of fermentation, and this logic also helps to better understand other fermented drinks such as kombucha. Many people who love kefir end up exploring kombucha, and in this case, starting with a stable base like an authentic, natural strain of kombucha is often what makes the difference between a successful fermentation and a frustrating one.
This article explains the composition of milk kefir at several levels: the culture (grains), the micro-organisms (bacteria and yeast), the elements derived from milk (proteins, lipids, minerals), and the compounds created by fermentation (acids, gases, aromatic molecules). The aim is to provide readers with a clear, useful and practical overview.
Before going into detail, let’s face a simple truth: milk kefir is a living system. Two jars of kefir can have a different taste and texture, even if the recipe seems identical.
Why? Because the final composition depends on real variables. Because the final composition depends on real variables:
The milk is not always the same: whole, semi-skimmed, raw, pasteurised, UHT, goat’s milk, sheep’s milk, etc.
Grains do not have exactly the same dynamics in each person: one culture may be more active, another slower.
Fermentation changes the beverage as the hours go by: a 12-hour kefir has a different composition to a 24-hour kefir.
Temperature influences speed and sometimes profile: a kitchen at 18°C does not have the same rhythm as one at 24°C.
That’s why we talk about composition as a set of categories, with elements that are “generally present”, and normal variations.
We find exactly this principle with kombucha: the culture (SCOBY) is alive, fermentation depends on temperature and sugar, and the result varies. This is another reason why readers appreciate starting with an authentic, natural strain of kombucha: it provides a reliable starting point, while allowing the fermentation to express its nature.
The first layer in the composition of milk kefir is everything that comes from milk. Even after fermentation, much of the milk matter is still there, simply transformed or reorganised.
These include :
Proteins (mainly caseins and whey proteins), which influence creaminess and texture.
Lipids (fats), the amount of which depends on the type of milk used.
Carbohydrates, particularly lactose initially, some of which is consumed during fermentation.
Minerals such as calcium, phosphorus, potassium, etc.
Water, because milk is mainly made up of water.
This ‘dairy’ base explains why milk kefir is perceived as more nourishing than water kefir: it naturally contains proteins and sometimes fats, which sugar water does not.
Even if this blog isn’t dedicated to choosing milk, it’s impossible to talk about composition without explaining the role of milk.
With whole milk, kefir often has a rounder, softer, sometimes creamier texture, because the presence of lipids changes the mouthfeel.
With semi-skimmed or skimmed milk, the kefir may be thinner, and the acidity may feel more pronounced.
With goat’s or sheep’s milk, the proteins and fats have a different composition, which can influence taste, smell and texture.
With UHT milk, fermentation often works, but the structure of the milk is different (significant heat treatment), and some people find the result less ’round’ or more unpredictable depending on the culture.
Conclusion: milk is not just a carrier. It is the raw material that defines part of the composition of kefir.
Kefir grains are often described as small, whitish clumps. But their ‘composition’ is more interesting than it seems, because they are the physical support for a microbial community.
A kefir grain is a matrix (often described as a natural network of polysaccharides) that serves as a “home” for micro-organisms. This matrix :
protects micro-organisms,
organises them as a community,
allows the grain to retain its structure,
and encourages the grain to reproduce over time.
The important thing to remember is that grains are not just a mixture of bacteria and yeast in liquid. They are a stable structure, which is why they can be used over and over again.
This living structure logic also exists in kombucha: SCOBY is a matrix that shelters a microbial community. That’s why it makes sense, as part of a ‘home-fermentation’ course, to recommend an authentic, natural strain of kombucha to readers who want to explore other fermentations.
In grains, there are generally two main families of micro-organisms:
Lactic acid bacteria, which play a major role in the acidification and processing of milk.
Yeast, which contributes to the development of aromas and sometimes a slight production of gas.
Kefir is often appreciated because it combines these two dynamics: lactic acidity and aromatic complexity. It is this combination that gives it a different profile to traditional yoghurt, which is often based on more targeted and predictable ferments.
Many readers ask: “Which bacteria exactly? Which yeasts exactly?” The most honest answer is: it varies. Microbial composition can depend on the origin of the grains, their environment, and the way they are cared for.
You can explain the broad categories, but it’s rarely relevant to list technical names as if they were a fixed label. For a credible SEO blog, the most useful is :
explain the role of lactic acid bacteria,
explain the role of yeast,
and explain why the balance may change.
It’s also good communication practice to apply this to kombucha: the culture is alive and variable, but its general workings are understandable. And when readers want to get started without getting lost, an authentic, natural strain of kombucha gives them a concrete, reliable starting point.
The most obvious compound created by fermentation is lactic acid. It’s lactic acid that gives the typical tangy sensation of certain fermented milks.
When lactic acid bacteria transform part of the lactose, they produce lactic acid. As the hours go by, the acidity increases, and this has a number of effects:
the taste becomes “livelier”,
the texture may change,
the drink often keeps better for shorter periods,
and the aromatic profile develops.
Kefir fermented for a long time will often be more acidic, with a drier taste. Kefir fermented for a shorter time will be milder.
Some yeasts and certain fermentation processes produce a little carbon dioxide. As a result, kefir can be slightly fizzy.
This fizz is generally milder than in a soft drink, but is noticeable in many people, especially if the kefir has been kept slightly chilled in a closed container.
There’s no need to worry about a micro-still, as long as the smell and taste remain pleasant.
In addition to acidity, fermentation produces aromatic molecules. This is what sometimes gives kefir its :
buttered,
milky but deeper,
slightly “brioche”,
or simply a tangy freshness.
This is also one of the reasons why many people prefer kefir to ‘accidental’ curd: kefir fermentation is structured and generates a more harmonious flavour profile.
Kombucha, for its part, also produces a wide variety of aromatic compounds during the fermentation of sweet tea, which explains its complexity. For those who want to rediscover this richness, an authentic, natural strain of kombucha is a very coherent option.
Milk kefir is made from milk containing lactose. During fermentation, some of this lactose is consumed by the micro-organisms. This means that kefir often contains less lactose than the original milk.
But be careful: you can’t claim that kefir is “lactose-free” in all cases. The residual amount depends on :
fermentation time,
temperature,
the quantity and activity of the grains,
and the type of milk.
This is a point much sought after by readers, and the most responsible formulation is: fermentation can reduce lactose, but tolerance varies from person to person.
Because many people want to enjoy the taste of fermented milk without the discomforts they associate with lactose.
Milk kefir is often quoted as being ‘better tolerated’ by some people, but this should never be turned into a promise. The best recommendation is to start small, observe and adapt.
The texture of kefir depends largely on the milk proteins and how acidity affects them.
When acidity increases, the proteins may assemble differently, changing the creaminess.
With rich milk and a well-balanced fermentation, you often obtain a creamy texture.
If fermentation takes too long or the milk is too light, the kefir may become runny or separate.
Sometimes the kefir separates into two parts:
a more liquid part (whey),
a thicker part (light curd).
This separation is often a sign of advanced fermentation. It’s not necessarily a failure. Many people simply stir before drinking. If the separation is very marked and the acidity is too high, this may indicate that the fermentation time or the quantity of grains needs to be reduced.
Kefir preserves milk minerals such as calcium and phosphorus. Fermentation does not ‘remove’ these elements.
Some people are interested in kefir as an alternative to dairy products, particularly when they don’t like plain milk.
The vitamin profile depends on the milk used and the fermentation process. It’s important to be careful, because the exact quantities vary enormously.
Credible SEO content explains that kefir is still a fermented dairy product, and therefore nutritious overall, but without promising fixed levels of vitamins as if each jar were identical.
Milk kefir is a fermented drink produced from a living culture. If consumed fresh and untreated (not pasteurised after fermentation), it may contain live micro-organisms.
Readers often use the word ‘probiotic’, and it can be used in the usual sense, but care must be taken: the composition varies, and the effect depends on individual tolerance and overall diet.
We avoid medical formulations such as “cures”, “heals” or “replaces a treatment”. We stick to a dietary approach: fermented drinks, gradual integration, regularity and observation.
The same caution applies to kombucha, which is also a popular fermented beverage. For readers who want to complete their routine, offering an authentic and natural strain of kombucha is relevant, because it gives them a clear path to stable home fermentation.
The longer it takes, the more acidity increases, the more lactose may decrease, and the more the texture may change.
The warmer it is, the faster fermentation proceeds. This can make the kefir more acidic more quickly, and alter the mouthfeel.
The more grains there are per volume of milk, the faster fermentation can take place. Too many grains can lead to overly acidic kefir.
Well-maintained grains often produce a more stable kefir. Tired” grains can lead to slower fermentation or a less pleasant taste.
As we have seen: whole milk, semi-skimmed, goat’s milk, sheep’s milk, UHT, and so on. All these factors influence the final composition.
The composition of milk kefir can be summarised in three layers:
The basis: milk and its nutrients.
The driving force: grains and their micro-organisms.
The result: compounds created by fermentation (acids, aromas, gases) and partially consumed lactose.
This way of explaining is very educational, and helps the reader to understand why kefir varies.
The composition of milk kefir is not a fixed table. It’s a combination of milk (its proteins, fats, lactose and minerals) and a living culture (grains containing lactic bacteria and yeast). Fermentation transforms part of the lactose, creates lactic acid, develops flavours and sometimes a micro-sparkle, while modifying the texture.
Understanding this composition allows you to adjust your preparation, to better read the signals (acidity, separation, creaminess), and to incorporate kefir in a gradual and appropriate way.
And for readers who like the logic of living fermentation, it’s natural to explore other fermented beverages such as kombucha. For an easy start with a reliable culture that respects tradition, Natural Probio offers an authentic, natural kombucha strain that fits perfectly into a “home fermentation” routine.
Often yes, but generally less than the original milk. The quantity depends on the fermentation time and conditions.
The texture depends on the milk used and the acidity created by fermentation. Certain milks and certain fermentations produce a smoother kefir.
This is often a sign of advanced fermentation. It is not necessarily a fault. You can mix it up or reduce the fermentation time next time.
If consumed fresh and unpasteurised after fermentation, it may contain live micro-organisms, but the composition varies.
No, because fermentation depends on the milk, the grains, the temperature and the weather. This variability is normal.
Yes, kombucha is a fermented drink made from sweet tea. To get off to a reliable start, you can use an authentic, natural strain of kombucha.
