White cabbage becomes sauerkraut, milk becomes yogurt, and soybeans become tempeh – all through fermentation. The gentle process not only makes vegetables and fruit last longer but also ensures a special taste. And because of its health-promoting properties, fermentation is becoming increasingly popular.
Fermentation is an ancient preservation method
Just like canning, fermentation is a method of preserving food – our grandmothers already knew that. Although fermenting has gone out of fashion over the years, it is currently making a real comeback.
Fermentation is a natural process in which microorganisms, such as bacteria and fungi, colonize food and convert the sugars and starches it contains into acid, which preserves the food.
This method of preserving food was probably discovered by accident: If food is left in the heat for too long, microorganisms multiply in it. If you are unlucky, it is mainly putrefaction bacteria, mold, or yeast that spoil the food. With a bit of luck, however, it will be the desired bacteria – they are called probiotic bacteria – that will start the fermentation.
Fermentation is therefore about creating optimal conditions for these desired bacteria (e.g. lactic acid bacteria) and at the same time counteracting the formation of putrefactive bacteria and fungi.
Fermented foods from all over the world
This fermentation process has been used for thousands of years, making it the oldest method of preserving food – around the world:
- In Japan, tempeh, miso, and soy sauces are made from fermented soybeans.
- The Koreans process Chinese cabbage into kimchi
- The Germans ferment white cabbage to make sauerkraut.
- Fish is fermented in Greenland.
- The cuisine of Thailand is home to over 60 fermented dishes.
- In Malaysia, fermented durian (stink fruit) is served as a side dish.
In fact, we eat fermented foods almost every day without even realizing it. Typical fermented foods in Europe include salami, sauerkraut, vinegar, sourdough bread, coffee, black tea, chocolate, all kinds of dairy products, and, increasingly, Korean kimchi.
Fermenting has a special tradition in Korea
Kimchi is considered the quintessential fermented product and is currently conquering the whole world. In Korea, it serves as a spicy-hot side dish for almost all dishes, whether breakfast, lunch, or dinner. Virtually every family has its own variant of fermented Chinese cabbage, the recipe of which is passed down from generation to generation. The production of kimchi, called Kim Jung, is an ancient tradition and is even on the list of intangible cultural heritage.
At kimjang, all the women in the extended family meet and then spend a whole day making kimchi – after all, it has to be enough for the whole winter. Depending on the recipe, the Korean national dish is made from Chinese cabbage, leeks, ginger, radish, chili, and cucumber. A few hundred heads of cabbage can easily be processed. However, Kim Jang is not only about making kimchi but also about strengthening social cohesion within the family and neighborhood).
Traditionally, kimchi is fermented in clay barrels and stored in them for several months. When there were no refrigerators, clay pots were dug in the garden so there was always a supply. Today, Korea even has kimchi refrigerators that were invented specifically to store the national dish.
The ingredients for fermented vegetables
For the variant presented here you need:
- Large bowl or pot
- Plate or lid that just fits into (don’t pay attention!) the bowl
- Pestle or large cooking spoon for mashing
- Something to complain about a glass
- mason jars
The preparation of fermented vegetables
If you have all the ingredients and the accessories together, you can start – as follows:
- Wash the vegetables thoroughly and cut into bite-sized pieces, then toss with salt and any other spices you like. The optimal salt content is 2% of the vegetable weight.
- Stir and mash until the brine completely covers the vegetables. If the brine is not enough, you can also add some water.
- Add the vegetables to the bowl along with the brine. Then place a plate directly on top of the vegetables to squeeze out any remaining air. Ideally, the brine should also cover the plate – this way the air can escape but the vegetables don’t float on the surface. The plate is then weighed down with heavy glass, for example. You should make sure that there is still some space left to the edge of the bowl, as the liquid will start to bubble during fermentation and could otherwise overflow.
- The vegetables should now stand at room temperature for at least 5 to 7 days.
Now you can do a first taste test. The longer the fermentation, the more intense the taste and the longer the shelf life.
- The vegetables are then filled into boiled preserving jars together with the brine, sealed tightly, and stored in the refrigerator or in a cool room. Refrigeration will stop fermentation as much as possible, but it will still progress a little, especially if the jars are not refrigerated. Therefore, the glasses should not be filled to the top here either, so that nothing can overflow.
- The fermented food should be refrigerated for a few months.
This is what happens when you ferment
The fermentation process behind this gentle preservation method can be easily explained using the above example of lactic acid fermentation: the finely chopped vegetables are mixed with salt and mashed to create the so-called brine. On the one hand, the salt pulls the water out of the vegetables and prevents rotting bacteria or mold from forming. The brine must completely cover the vegetables to prevent oxygen from reaching the vegetables. Because the oxygen would attract putrefactive bacteria and/or mold could form.
Airtight but protected, the lactic acid bacteria can now start lactic acid fermentation: the starch and the sugar are converted into lactic acid, which creates an acidic environment. This gives the vegetables their sour aromas and in turn, ensures that no putrefactive bacteria and no mold can settle. As a result, fermented vegetables have a longer shelf life.
Starter cultures for fermentation
But where do these microorganisms actually come from? If you want to produce lactic acid fermented vegetables, there are usually enough of these microbes on the vegetables (ideally organic vegetables).
But if you want to make kefir, yogurt, tempeh, or kombucha, for example, you have to add a bacterial culture, the so-called starter culture, so that the fermentation process succeeds. You can buy such starter cultures on the Internet, but also in some health food stores and health food stores.
Tempeh starter culture
The starter culture for tempeh contains the fungus Rhizopus Oligosporus. Tempeh is made from soybeans – these serve as a breeding ground for the fungus. The Rhizopus Oligosporus grows and coats the soybeans, making them into a firm loaf.
Starter culture for miso and soy sauces
To make your own miso and soy sauce, you need a starter culture called koji. This is fermented rice that is used in many traditional dishes in Japanese cuisine. Koji can be found in Asian shops or in online shops with Japanese products. If you want to make koji yourself, you need the mold Aspergillus oryzae as a starter. This is also available in said online shops.
Starter culture for water kefir
Water kefir, i.e. vegan kefir, is unfortunately not commercially available, but you can easily make it yourself. For this you need so-called kefir crystals: These consist of yeasts and lactic acid bacteria, which stick together in small clumps – the crystals.
Fermenting creates a variety of flavors
We also have these microorganisms to thank for the abundance of flavors that develop during fermentation. And as different as tastes are, so are the microbes that are at work. For example, it is the acetic acid bacteria in apple cider vinegar, specific molds in tempeh and soft cheese, and the lactic acid bacteria in yogurt and kimchi that lead to fermentation and create this variety of flavors.
The fermentation acts like a natural flavor enhancer. The storage time is crucial: the longer the fermented food is stored, the more acidic it tastes – at least in the case of vegetables. Storage at cool temperatures largely, but not completely, stops the fermentation. This can change the taste a bit.
That’s why fermented foods are so healthy
The fermented dishes not only taste different now, but they are also very healthy. The probiotic bacteria that settle in fermented food are also part of our own intestinal flora. And this is exactly what plays an important role in our immune system.
The healthier the intestinal flora is, the better it can prevent the colonization of pathogens, the healthier the intestinal mucosa is and the better the person is protected from chronic diseases of all kinds.
The probiotic bacteria from fermented foods now contribute to the described healthy and balanced intestinal flora. Just like fermentation in food, the bacteria in the gut create a slightly acidic environment, making it difficult for disease-causing bacteria to survive there ( 2Trusted Source ). Well-known probiotic bacteria are, for example, lactobacteria (= lactic acid bacteria) and bifidobacteria.
In addition, the probiotic bacteria already break down the cell structures of the corresponding food during the fermentation process – they are, so to speak, already pre-digested. This makes them easier to digest in our bodies. So, by fermenting, you can easily make your own probiotic foods at home.
A 2017 review, published in the journal Critical Reviews in Food Science and Nutrition, examined several studies on fermented foods and found that fermented foods, such as vegetables, fruits, miso paste, and vinegar, have a variety of benefits. For example, they reduce the risk of diabetes, high blood pressure, obesity, diarrhea, and thrombosis. How much-fermented food people should consume in order to benefit from these properties, however, still needs to be further investigated.
These vegetables are suitable for fermenting
So now you know how fermentation works and its benefits. Now you can try it yourself. There are no limits to your creativity: You can use all sorts of vegetables, for example, peppers, courgettes, beetroot, broccoli, radishes, fennel, fresh olives, chili, cucumbers, garlic, mushrooms, radishes, or tomatoes.
Just keep in mind that the consistency of the vegetables will also change during fermentation. While soft vegetables such as tomatoes break down more quickly, hard varieties such as cauliflower retain a crunchy bite. The consistency depends on how long the vegetables have been fermented.