Sauerkraut, kimchi, or fermented pickles have one thing in common: lactic acid bacteria play a central role in their production. This form of fermentation is known as lacto-fermentation or lactic acid fermentation.
The term may sound like milk or lactose at first. In fact, however, lacto-fermentation does not automatically have anything to do with dairy products. Vegetables, fruit, or other plant-based foods can also be fermented using lactic acid bacteria.
But what exactly happens during lactic acid fermentation? What role do lactobacilli play? And why does this process make vegetables sour and give them a longer shelf life?
What does lacto-fermentation mean?
Lacto-fermentation is a form of fermentation in which lactic acid bacteria convert carbohydrates into lactic acid and other metabolic products.
Among other things, lactic acid ensures that the pH value of the food drops. This creates the characteristic acidic aroma of many fermented foods and, at the same time, an environment in which many unwanted microorganisms struggle to multiply.
Lactic acid fermentation has therefore been used for centuries to produce and preserve food.
Typical examples are:
- Sauerkraut
- Kimchi
- fermented pickles
- fermented carrots
- Yogurt
- Kefir
- Sourdough
With fermented vegetables, fermentation often occurs spontaneously due to microorganisms naturally present on the vegetables. In professional food production, specifically selected starter cultures can also be used.
Why is it called "lacto-fermentation"?
The term "lacto" is often mistakenly associated with lactose or milk.
However, it actually refers to lactic acid.
Vegetables also contain carbohydrates that certain microorganisms can utilize during fermentation. This produces, among other things, lactic acid.
That is why even completely plant-based foods can be lacto-fermented.
Lacto-fermentation therefore does not mean that milk or lactose must be present.
What are lactic acid bacteria?
Lactic acid bacteria are a group of bacteria that metabolize carbohydrates and primarily produce lactic acid in the process.
They play an important role in food production. They are used, among other things, in the fermentation of vegetables, dairy products, sourdough, and other foods.
In fermented vegetables, lactic acid bacteria are often among the microorganisms that multiply particularly rapidly during the fermentation process and shape the course of fermentation.
This does not involve a single type of bacterium. Various genera and species are grouped together under the term lactic acid bacteria.
What are lactobacilli?
Lactobacilli are among the best-known lactic acid bacteria.
The term "lactobacilli" was long used for bacteria of the Lactobacillus genus. Due to a scientific reorganization, numerous species have since been distributed into various new genera.
In general usage, however, they are still frequently referred to as lactobacilli.
Various representatives of this group occur naturally on plants or food and can be involved in lactic acid fermentation.
It is important to note: Not every lactic acid bacterium is a lactobacillus, and not every lactobacillus automatically fulfills the criteria of a probiotic.
How does lactic acid fermentation work?
Simply put, lacto-fermentation can be explained in several steps.
1. Microorganisms are on the food
Fresh vegetables are not sterile. There are various microorganisms on their surface.
These can also include lactic acid bacteria.
2. The vegetables are prepared
For vegetable fermentation, the vegetables are, for example, chopped, grated, or processed whole.
Subsequently, salt is often added or the vegetables are placed in a brine.
The salt influences the microbial environment and helps to create conditions under which certain microorganisms can develop better than others.
3. Oxygen is reduced as much as possible
The vegetables are kept completely submerged under the liquid or brine.
This creates low-oxygen conditions, which are important for many forms of vegetable fermentation.
4. Lactic acid bacteria multiply
The lactic acid bacteria use the available carbohydrates as an energy source.
In the process, various metabolic products are created, particularly lactic acid.
5. The pH value drops
As lactic acid production increases, the food becomes more acidic.
This changes the taste, aroma, and microbiological conditions.
Many unwanted microorganisms struggle to multiply in this acidic environment. This is precisely why lactic acid fermentation was historically an important way of making food last longer.
What exactly happens during lactic acid fermentation?
Lactic acid fermentation is a complex microbial process.
The microorganisms involved not only change the acidity of the food, but also its aroma, texture, and composition.
Which microorganisms dominate during fermentation depends on, among other things:
- The starting food
- Salt concentration
- Temperature
- Fermentation duration
- Oxygen availability
- Natural microbial composition
- Any starter cultures used
Particularly with spontaneously fermented vegetables, the microbial community changes over the course of the fermentation. Different microorganisms can dominate in succession.
What is lacto-fermented vegetable?
"Lacto-fermented vegetable" refers to vegetables that have been fermented primarily with the help of lactic acid bacteria.
Well-known examples include:
- Sauerkraut
- Kimchi
- fermented pickles
- carrots
- radish
- beetroot
- cauliflower
- cabbage
- bell peppers
Basically, many types of vegetables can be fermented.
The lactic acid fermentation of cabbage is particularly well known. In classic sauerkraut, white cabbage is shredded, salted, and fermented with minimal oxygen.
During this time, various lactic acid bacteria take over the fermentation step by step.
Fermented vegetables and pickled vegetables: What is the difference?
Fermenting and pickling are not the same thing.
In classic pickling, for example, vinegar is added to a food. The acid is added from the outside.
In lactic acid fermentation, however, the acid is created through the metabolic activity of microorganisms.
A vinegar pickle is therefore not automatically fermented.
Fermented pickles, on the other hand, become sour with the help of microorganisms and usually a salt brine.
The difference therefore lies primarily in how the acid is created:
Pickled: Acid is added.
Lacto-fermented: Lactic acid is created during fermentation by microorganisms.
What role does salt play in lacto-fermentation?
Salt is an important ingredient in many vegetable fermentations.
It fulfills several functions:
- It draws water out of the vegetables.
- This allows a natural brine to form.
- It influences the activity of different microorganisms.
- It can inhibit unwanted microorganisms.
- It influences taste and texture.
The correct salt concentration is therefore an important factor for controlled fermentation.
Too little or too much salt can alter the course of the fermentation.
Why must fermented vegetables remain under the brine?
In many vegetable fermentations, the vegetables should remain completely covered by liquid.
This reduces contact with oxygen.
This supports the conditions under which the desired fermentation processes can take place and can simultaneously make it difficult for certain unwanted microorganisms to grow on the surface.
For this reason, weights are often used during fermentation to keep the vegetables under the brine.
Are lactic acid bacteria naturally present on vegetables?
Yes. Fresh vegetables carry a diverse community of microorganisms on their surface.
Lactic acid bacteria often represent only a small part of this microflora initially. Under suitable fermentation conditions, however, they can multiply strongly and eventually dominate the process.
This is precisely what makes spontaneous vegetable fermentation possible.
Alternatively, manufacturers can purposefully add selected lactic acid bacteria as starter cultures to make the fermentation process more controlled and reproducible.
Spontaneous fermentation or starter culture: What is the difference?
In spontaneous fermentation, no specific microorganisms are added.
Instead, the microorganisms that are naturally present on the food and in its environment are used.
In fermentation with a starter culture, on the other hand, specifically selected microorganisms are added.
This can help to make the fermentation process more controlled and achieve a more reproducible result.
In modern food production, therefore, specially selected starter cultures are often used.
Does lacto-fermented vegetable contain live lactic acid bacteria?
That depends on the further processing.
Fresh, unpasteurized lacto-fermented vegetables can still contain live lactic acid bacteria when consumed.
However, if the product is heated or pasteurized after fermentation, many of the microorganisms are inactivated.
Therefore, the same applies here:
Lacto-fermented does not automatically mean that live cultures are still present in the finished product.
Manufacturing, processing, and storage are the deciding factors.
Are lactic acid bacteria automatically probiotics?
No.
Lactic acid bacteria and probiotics are not synonymous.
For microorganisms to be labeled as probiotics, certain scientific requirements must be met. Among other things, specific microorganisms must be defined and have a proven health benefit in sufficient quantities.
In spontaneous vegetable fermentation, on the other hand, numerous different microorganisms can be involved.
Therefore, one cannot automatically conclude that a fermented vegetable is probiotic just because lactic acid bacteria are present.
Is lacto-fermentation healthy?
Fermented vegetables are the subject of numerous scientific studies.
Research is being conducted on how fermentation affects:
- the microbial composition
- nutrient content
- plant-based ingredients
- taste and aroma
- shelf life
Lactic acid fermentation can change the composition of plant-based foods. Depending on the food, microorganisms, and fermentation conditions, different metabolic products can be created.
Nevertheless, the blanket statement "lacto-fermentation makes food healthy" would be too broad.
The health profile of a fermented food always depends on the specific product, its composition, processing, and the quantity consumed.
What changes when fermenting vegetables?
The fermentation process can change vegetables in several areas.
-
Taste:
Lactic acid provides the typical sour taste. -
Aroma:
During fermentation, numerous other metabolic products are created that influence the aroma. -
Texture:
Depending on the food and fermentation time, vegetables can become firmer, softer, or more tender. -
Shelf life:
The increasing acidity can create conditions under which many spoilage organisms grow less well. -
Plant-based ingredients:
Microorganisms can convert various components of the vegetable during fermentation. Exactly what changes occur depends heavily on the raw material and microorganisms.
Which foods are produced through lactic acid fermentation?
Lactic acid fermentation is not limited to vegetables.
Lactic acid bacteria also play an important role in other foods.
These include, among others:
-
Sauerkraut:
Fermented white cabbage. -
Kimchi:
Traditionally Korean fermented vegetables. -
Yogurt:
Lactic acid bacteria convert part of the milk sugar into lactic acid. -
Kefir:
Here, various bacteria and yeasts work together. -
Sourdough:
Lactic acid bacteria and yeasts work together, influencing the aroma, structure, and acidity of the dough.
Lactic acid bacteria are therefore an important component of many different traditional food cultures.
Lacto-fermentation, alcoholic fermentation, and acetic acid fermentation: What is the difference?
Not every fermentation process is the same.
In lactic acid fermentation, lactic acid bacteria primarily produce organic acids, especially lactic acid.
In alcoholic fermentation, yeasts mainly convert sugar into alcohol and carbon dioxide.
In processes involving acetic acid bacteria, alcohol can be converted into acetic acid in the presence of oxygen.
In many fermented foods, several microorganisms work together. Traditional fermentation processes are therefore often more complex than a single chemical reaction.
Can you lacto-ferment vegetables at home?
In principle, vegetables can also be fermented at home.
However, it is important to work cleanly, use appropriate salt concentrations and suitable temperatures, and avoid unwanted contamination.
Typically, vegetables are:
- washed and prepared,
- salted or covered with brine,
- kept completely submerged in the liquid,
- fermented at a suitable temperature,
- then stored in a cool place.
If there is an unusual smell, noticeable mold, strong discoloration, or other signs of spoilage, the product should not be consumed.
Anyone fermenting at home should therefore follow proven recipes and maintain hygienic working practices.
Frequently asked questions about lacto-fermentation
What is lacto-fermentation?
Lacto-fermentation is a form of fermentation in which lactic acid bacteria utilize carbohydrates, producing lactic acid among other substances. This lowers the pH value and can alter the taste, aroma, and shelf life of the food.
Does lacto-fermentation have anything to do with lactose?
No. In this context, "lacto" refers to lactic acid, not to the presence of milk or lactose. Vegetables can also be lacto-fermented, making them completely plant-based.
What are lactic acid bacteria?
Lactic acid bacteria are various types of bacteria that can ferment carbohydrates, primarily producing lactic acid. They play an important role in the production of many fermented foods.
What are lactobacilli?
Lactobacilli are a well-known group of lactic acid bacteria. Many species previously classified under the genus Lactobacillus have since been scientifically reassigned to new genera.
Which vegetables can be fermented?
Many types of vegetables are generally suitable for lactic acid fermentation. Particularly well-known examples include white cabbage, Chinese cabbage, cucumbers, carrots, radishes, red beets, or cauliflower.
Is fermented vegetable always lacto-fermented?
No. While lactic acid fermentation is one of the most common forms of fermentation for vegetables, other microorganisms and fermentation processes can also be involved.
Is lacto-fermented vegetable probiotic?
Not automatically. Lacto-fermented vegetables may contain live lactic acid bacteria if they have not been heated after fermentation. However, the presence of live bacteria alone is not enough to scientifically classify a food as probiotic.
Is sauerkraut lacto-fermented?
Traditionally produced sauerkraut is created through lactic acid fermentation and is therefore a classic example of lacto-fermented vegetable.
Is kimchi lacto-fermented?
Yes. Lactic acid bacteria play an important role in traditional kimchi production. The exact microbial composition changes during fermentation.
Why do fermented vegetables turn sour?
During fermentation, organic acids—especially lactic acid—are produced. This lowers the pH value of the food and creates the typical sour taste.
Conclusion: Lacto-fermentation is fermentation with lactic acid bacteria
Lacto-fermentation, or lactic acid fermentation, is a traditional form of food production in which lactic acid bacteria convert carbohydrates.
This produces, among other things, lactic acid. It provides the typical sour taste and contributes to changing the microbial conditions within the food.
The method is particularly well-known for lacto-fermented vegetables such as sauerkraut, kimchi, or fermented cucumbers.
The term "lacto" does not imply that milk must be present. The crucial factors are the lactic acid bacteria involved.
It is also worth distinguishing carefully between terms like lactobacilli, live cultures, or probiotics: not every lactic acid bacterium is a lactobacillus, and not every fermented food with live lactic acid bacteria is automatically probiotic.
These very microbial processes make lacto-fermentation one of the most versatile forms of traditional food production.
