Frau Mandt, in den sozialen Medien gibt es unzählige Videos darüber, wie Gemüse fermentiert wird – wie erklären Sie sich den Hype?
We see various reasons: On the one hand, DIY culture is in vogue on Instagram, coupled with a kind of return to old “honest” techniques. This is particularly true in the food sector. Sourdough bread is also experiencing a renaissance. When it comes to fermented foods, there is also a strong emphasis on health aspects in social media – on the one hand, that no artificial preservatives are used, but sometimes there are also superfood promises for which there is not necessarily scientific evidence.
What exactly is fermentation?
Fermentation is a generic term for various metabolic processes in which microorganisms break down organic material in food and form new compounds. These include lactic acid, acetic acid and alcoholic fermentation as well as mold-related processes such as those found in certain types of cheese or soy sauce. Fermentation has been used for preservation for thousands of years and contributes to a special flavor development.
How does fermentation work?
During lactic acid fermentation, lactic acid bacteria convert the sugar contained in vegetables into lactic acid without oxygen. The pH value drops, creating an acidic environment that inhibits or kills harmful germs. This is how the vegetables are preserved and get their typical sour taste.
What is important for the start?
You don’t need the full range of fermentation accessories. To get started, a few large mason jars with a wide opening will also work. It is also important to use weights that press the vegetables completely into the resulting brine. There are special fermentation weights, but clean stones are also suitable for starters. Of course you also need clean, unsprayed vegetables, preferably from your own garden, salt without additives such as anti-caking agents and water. Conventional table salt often contains so-called anti-caking agents so that it does not absorb moisture and does not clump together. These include calcium or magnesium carbonate. Starter cultures are usually unnecessary because there are already naturally occurring lactic acid bacteria on the surface of the vegetables.
Which vegetables are particularly suitable for beginners?
For fermentation beginners, I can recommend particularly robust and uncomplicated vegetables, such as white cabbage, which fermentation turns into sauerkraut and which is very forgiving. Pickled cucumbers, carrots and beetroot are also suitable. Very water-rich vegetables such as tomatoes or cucumbers with thin skins are generally less suitable.
What are the differences between dry and wet fermentation methods?
During dry fermentation, the prepared vegetables are rubbed directly with salt or kneaded. The salt removes water from the vegetables, which forms a natural brine after a while. This method is particularly suitable for types of cabbage such as white cabbage for sauerkraut, but also for cucumbers and radishes. Wet fermentation, on the other hand, works according to a different principle: Here the vegetables are placed in a prepared brine, which typically has a concentration of two to three percent – there are 20 to 30 grams of salt per liter of water. This method is ideal for harder vegetables or when different vegetables need to be fermented together. This allows for more even fermentation.
What happens to the vegetables during the fermentation process?
The pH value drops from around 7 to 3.5 to 4. This means the vegetables last longer. It becomes softer, ideally remains al dente and tastes sour, often a little salty. The vitamin C content is maintained and can even increase. Sometimes soy also produces vitamin B 12. Probiotic bacteria also proliferate, which can support digestion.
What salt concentration do you recommend?
The salt fulfills several functions during fermentation: It draws water out of the vegetables, slows down unwanted germs and gives the lactic acid bacteria the best conditions. How much salt you use depends on the method, vegetables and cut. When dry salting, you usually calculate two to 2.5 percent of the vegetable weight – for a kilo of cabbage that means 20 to 25 grams. When wet fermenting, you stir two to three percent salt into the water (20 to 30 grams per liter) and put the vegetables in it. If you cut finely, juice comes out more quickly and you can often get by with a little less salt; With coarse pieces or whole pieces you need more so that the fermentation gets off to a good start.
How long does fermentation take?
This depends on temperature, salt content and desired taste. At room temperature, the active phase usually begins after three to seven days: bubbles show the work of the bacteria. Without vessels with a valve, jars should be opened once a day during this time to avoid excess pressure.
When is the fermentation? „complete”?
After the first lively phase, the ferment matures for another two to four weeks in a cool storage area or in the refrigerator. The aroma deepens. Then it’s time to try it: the fermentation is “finished” when the desired level of acidity is reached.
Suppose there is mold in my glass – what did I do wrong and how harmful is it?
Check regularly how your glasses are doing: If you see unusual discoloration, smell strange or show signs of mold, you should take it seriously. Mold is usually caused by small mistakes that can easily be avoided. For example: If there is too little salt in the glass, unwanted microorganisms feel particularly comfortable. If pieces of vegetables stick out of the brine and come into contact with air, they can also become moldy. Even utensils that are not completely clean can quickly introduce germs or mold spores into the glass. And if it is stored too warm, mold will also grow faster. Spoiled vegetables are easy to recognize: a foul smell – different from the normal sour ferment smell -, a greasy consistency or unusual discoloration are clear signs. In this case, discard the ferment completely. Important to know: As soon as mold has formed, the entire ferment is inedible and must also be removed completely – it is not enough to just skim the mold off the top.
How long do ferments last in the fridge?
A big advantage of fermented vegetables is their long shelf life. During the first one to two weeks at room temperature, the taste and consistency change significantly – so it should be eaten quickly during this time. However, it often remains edible in the refrigerator for many months.
What advantages have been proven?
The health benefits of fermented vegetables are only partially scientifically proven. Some probiotic effects have been proven: The lactic acid bacteria formed during fermentation can have a positive effect on the composition of the intestinal bacteria. There is also evidence of the increased bioavailability of some nutrients and the better digestibility of dairy products, for example. However, many superfood promises are wishful thinking, according to which fermented foods are considered a detox miracle weapon or are said to have a general healing effect on serious illnesses.
Are there groups of people who should be careful?
Yes, because some lactic acid bacteria convert the amino acid histidine into histamine during fermentation. Aged cheese, yogurt, kefir, sauerkraut, kimchi, pickled cucumbers, miso, soy sauce, tempeh and drinks such as wine, beer and kombucha can be problematic for people with histamine intolerance. Immunosuppressed people and pregnant women should also avoid home-fermented foods to minimize the risk of harmful bacteria.
How climate-friendly is fermentation compared to freezing or drying?
In contrast to freezing or industrial drying, fermentation requires practically no energy – neither for the fermentation process itself nor for the subsequent storage for months. The costs are also kept within limits if you don’t buy all the accessories right away. It is particularly good for your wallet and the environment to buy regional, seasonal vegetables cheaply in large quantities or to harvest them in your own garden and then ferment them for later consumption. However, we do not have any concrete calculations beyond that.
