Lunch ‘n’ learn: fermentation 101

We’ll take a first peek into the magical, bubbly world of fermentation, by making our own Korean-style “Sauerkraut” called Kimchi. We’ll go over a few other quick vegetable pickling ideas, learn the easiest way to sterilise preserves jars and introduce some nutritious fermented products that you can play around with in your own kitchen.

Workshop Notes

I have learned most of the basics about vegetable fermentation from the bible on this topic, “The Art of Fermentation” by Sandor Katz. These notes are based on this wonderful resource, which I highly recommend to have at your side during your fermenting adventures.

Fermenting vegetables (and some fruit!) is a good, gentle introduction to fermentation because it is easy, quick, does not require special equipment, is safe, and produces delicious and nutritious results. This is what we focus on in this workshop, but there are a multitude of other fermentation possibilities, including drinks (wine, beer, kombucha), grains, tubers, beans, seeds and nuts!

The basics

Fermentation occurs when the veggies are submerged in water — a medium where oxygen-dependent organisms cannot thrive. Here, lactic acid bacteria feed on the sugars from the veggies and produce lactic acid and carbon dioxide. The lactic acid lowers the pH of the water, making it unfavourable for other harmful bacteria.


Salt is not strictly necessary but it helps with preservation by making the water medium unsuitable for harmful bacteria, slowing down the fermentation process and contributes to the taste and texture of the final product by helping the veggies retain their structure.


In general, the lower the temperature, the slower the fermentation. When fermenting at home, therefore, note that the process will go quicker in summer and slower in winter. Veggies requiring a longer fermentation process, such as Sauerkraut, can also be done in a cool room such as a cellar. When you are satisfied with the taste of the veggies and want to stop fermentation, place the jar in the fridge.

Sterilizing Jars

Clean equipment is an important part of the fermentation process, and reduces the risk of contamination, so it is worthwhile to take the time to properly sterilize the fermentation containers. Also make sure to use non-reactive materials, such as glass or stainless steel, for all stages (bowls, utensils and jars). For the fermentation process, I sterilize my glass jars by washing them well with soap and water, placing the lids and rubber liners in boiling water for a few minutes, and using one of the following two methods for the jars ONLY (no lids/rubber liners in the oven):

  • Place the jars without lids or rubber liners in a 120°C oven for around 15 mins. OR
  • Fill the jar to the rim with boiling water and let stand for a few minutes.

Even when care has been taken during the sterilization process, it is still possible that some mold begins to develop on the surface of the liquid which is in contact with oxygen. White mold means it hasn’t started producing spores yet. As the mold develops spores, it becomes colourful and can contaminate veggies further down, making them mushy and eventually mold-y tasting. Remove as much of the mold as you can, as soon as you can. Then check the veggies underneath: if they are mushy, remove and discard.

Use your sight, smell and taste senses and check your jar often! Don’t consume anything that looks/smells/tastes like mold.

To help reduce or prevent mold from developing on the surface, protect the fermenting veggies by covering them with big cabbage leaves which can be discarded at the end of the process. Or try covering the surface with a layer of olive oil.

The procesS

As Katz outlines in his book, the process for fermenting veggies is very simple:

  1. Chop or grate the veggies: the shape determines how much surface area is exposed, which influences the speed of fermentation, texture and taste.
  2. Salt: either dry-salt by massaging/lightly pounding it into the veggies or by soaking them in brine for a few hours.
  3. Add other seasoning, if desired. For kimchi, for example, a potent ginger-garlic-chili paste is rubbed into the cabbage for flavour. Or throw in some fresh herbs, bay leaves, pepper corns…
  4. Pack the veggies, pressing tightly so they are submerged by their liquids. Add water to cover, if necessary.
  5. Wait: the fermentation process can be as quick as a few days, weeks, months or even years! Keep an eye on your jars, and taste frequently.
Vegetables to use

Different cultures throughout the world preserve a wide variety of vegetables and fruit by fermentation, from roots, to squashes, tomatoes, lemons and watermelon rinds! There’s nothing you can’t try, however, not all fermentation processes suit all vegetables. Some, like zucchini, become too soft if left to ferment too long, while dark leafy greens such as kale or chard develop a strong, special flavour, and may work better as part of a mix with other veggies.

It’s pumpkin season now, so try fermenting some! If it has a tough rind, you can peel it and then continue with the process as outlined above. In winter, try root vegetables like beetroot, turnip, parsnip or parsley root. Use raw veggies! If you cook them, you will kill the naturally occurring lactic acid bacteria and will have to manually add a culture to start the fermentation process.

In this workshop we look at Kimchi, a Korean staple made from fermenting cabbage with optional other vegetables and a potent ginger-garlic-chili paste. I find it a good place to start, because it is easy to make, can already be eaten after a few days, and it is fun to play around with adding different vegetables, varying the amount of chili, etc. The recipe for basic kimchi we made in the workshop can be found below the notes.

Fermenting soy

A quick note about some fermented soy products we enjoyed at lunch:

Soy sauce is an ancient condiment originating in China over 2,000 years ago. The basic ingredients are soy beans, water, the Aspergillus oryzae or Aspergillus sojae molds, and often a grain such as wheat. If the wheat is omitted, the sauce is then gluten-free and referred to as Tamari.

Miso is a traditional Japanese condiment produced from the same ingredients as soy sauce, using grains such as rice or barley. High in protein and rich in vitamins and minerals, it is best not to expose it to high heat before consuming — add to soups or sauces only at the end of the cooking process.

Tempeh is a tofu-like product originating in Indonesia. It is made from whole, partly-cooked soy beans, to which a fermentation culture has been added. The mixture is left to ferment for a few days at a warm temperature. Its retention of the whole soy bean and the fermentation process make it higher in protein, dietary fiber and vitamins than tofu. In Bern, tempeh is available in some bio stores like Egli at the train station. I like the Futur Naturprodukte brand, a Swiss company using organic, Swiss soy. They also make delicious tofu (much better than the standard Migros/Coop brands).


Kimchi is a Korean staple, and there are as many versions of it as there are households and restaurants in Korea 🙂 There is, therefore, no one correct Kimchi recipe. Play around and adapt it to suite your taste!

  • 1kg cabbage, thinly sliced
    • I like to use Nappa cabbage (Chinakohl in German).
  • 250g radish (Bierretich, for example) or carrots or a mixture of both.
    • Grated or chopped into matchsticks.
  • 3-4 green onions, sliced thinly
  • ~75g sea salt
  • 5g sugar, optional
  • ~25g grated ginger
  • ~5 garlic cloves, smashed
  • Chilli flakes
    • Traditionally, Korean chilli flakes called Gochugaru are used, but since those are harder to come by in Bern, I use regular chilli flakes which are widely available in the super market or Turkish chilli powder available in some Middle Eastern or Asian stores. The type of chilli you use will influence the spiciness and flavour of the final result, so adapt according to what you have on hand and your personal preferences.
  1. Combine the cabbage and salt in a big bowl and massage with your hands until the cabbage has wilted and released its juices. It usually just takes a few minutes.
  2. Add water to cover the cabbage, then cover with something heavy to press it down.
  3. Let the cabbage marinate in the brine for a few hours. If pressed for time, one hour is enough.
  4. In the meantime, combine the garlic, ginger and chilli flakes and mash together to form a smooth paste. A pestle and mortar works well but is not strictly necessary.
  5. Drain the cabbage well and gently squeeze out the brine.
  6. In the bowl, combine the cabbage, radish/carrot, spring onions and ginger-garlic-chilli paste, and massage well with your hands until everything is well coated.
  7. Put in a clean jar and press down well so that the juices cover everything. Add a little water if necessary.
  8. Let ferment at 20°C for three days or more. Check and taste every day until desired flavour has developed. The kimchi can then be stored in the fridge for several weeks. Note that carbon dioxide is released during fermentation, especially in the beginning stages, so you may see some bubbles or hear a pop when you open your jar to taste it. This is normal!

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