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How to ferment vegetables (lacto-fermentation)

This article aims to give you a basic understanding of how to make fermented vegetables. You'll see how it is easy to make!

What's a "Lacto"?

The process of fermenting vegetables is often called "Lacto-fermentation", or "Lacto". This is because this fermentation uses Lactic Acid Bacteria (LAB).

Among allof the lactic fermentation recipes, there is naturally sauerkraut, kimchi, pickles and olives, but also milk-based products (yogurt, kefir, cheese...) and meat-based (dry sausage).


How to ferment veggies

Fermenting vegetables can be summarized in 5 easy steps:

  1. Cut up your vegetables
  2. Mix with salt
  3. Let them ferment at room temperature
  4. Limit oxygen presence
  5. Wait a few days, or a few months, and enjoy!

 And, every recipe could be boiled down to this formula:



Cutting vegetables for fermentation


If a vegetable is edible raw, then it will be edible fermented. Any type of vegetable will work! Their taste and texture will certainly change.

You can clean your vegetables with running water, but remember that lactic acid bacteria are on the skin of vegetables. Without these bacteria, no fermentation.


Lactic Acid Bacteria (LAB) are in the soil of the field and migrate on the vegetable as it grows. When you harvest your vegetables, they are already full of lactic acid bacteria. So there is usually no need to add any.

However, if your ingredients are sterile (like after cooking them), or if you want to speed up the fermentation process, or if you want to do it in a more controlled environment, then there are two techniques to add needed bacteria:

  1. Either buy Lactic acid bacteria for vegetables (Caldwell).
  2. Or you can add liquid that remains at the bottom of one of your previous jars of lacto-fermented vegetables (this brine is full of lactic acid bacteria).

The salt

Salt is used to promote the good bacteria, and prevent the bad.

The minimum amount of salt needed is 1% of the weight of your ingredients. This is not much, but you might want to add more based on taste. If you do a little batch, you could simply add salt to your taste. It will probably be above 1%. But if you do a medium size or big amount, you need to weigh your ingredients to make sure you have a good balance of salt, and a proper fermentation.

Any salt will work, but it needs to be without any additives! Look at the list of ingredients in your salt, it should only contain "salt". No iodine, or anti-caking agents. Iodine would prevent proper fermentation and anti-caking agents can disturb the taste. You can use whatever salt you want (pink, grey, white, fine, or coarse...), but the only ingredient needs to be salt.

The more salt there is, the slower the fermentation and the crisper the vegetables will be for a long time. Salt is a natural preservative that slows down biological processes.

The percentage of salt applies to the weight of the vegetables, or the water (if using brine). So, for a 2% sauerkraut recipe, you weigh your cabbage and you add 2% of that weight in salt. For example, 2% salt of 1000 g of cabbage = 20 g of salt. Idem, 1 liter of brine at 3% is done by adding 30 g of salt in 1 liter of water (1 litre of water weighing 1000 g).

We use the metric system because it's much easier to work with percentages... 2% of 1 pound (0.45 kg) is... 0.32 ounces (9 g). If you don't have it already, we advise you to buy a kitchen scale. It's very affordable and will help you create perfect recipes.

The water

Water is used if you make vegetables in brine (water + salt). Any water is suitable, but be careful with chlorine. If your water is chlorinated, then let it rest in a jar before mixing it with the vegetables. Chlorine will evaporate in about 30 minutes


No oxygen!

A lacto-fermentation is an anaerobic fermentation, which means that it does not require oxygen. A lactic fermentation could work in the presence of oxygen, however it will not be optimal. But above all, the presence of oxygen promotes the development of yeast and mould, because they need oxygen to develop...

You need to find a strategy to limit the presence of oxygen!

The idea is to keep vegetables under the liquid. Like that, they will not be in direct contact with oxygen (even if they are in your jar). That's why we use weights (or use tools to do the same).

But if you want there to be no oxygen at all, then two techniques are available to you:

  1. Use an air-lock. This will allow the CO2 to come out and prevent the air from returning. Very practical technique for all types of recipe volumes (fits a Mason jar, like a 50 litre boiler).
  2. Put it under vacuum. Very practical technique to make small portions.

The temperature

The hotter it is, the quicker the fermentation will be. Under 15 °C (59°F), the fermentation will be very slow. Above 30°C (86°F), fermentation will not be optimal (so it is not recommended). In a refrigerator, between 0 and 4°C (32-40°F), the fermentation will stop completely (or almost).

So if you don't want mold to grow in your half-consumed sauerkraut pot, the best thing is to keep it in the fridge.

Fermentation length

You can eat your fermented vegetables as soon as you want. We advised you to wait at least a week (for proper acidity, and health), but the fermentation time is mostly a matter of taste. You can extend the time before you open your container. So the flavors will be more developed.

With, or without brine?

Brine is simply salt + water. We use brine when we want to keep our whole vegetables, or in large chunks and so it is not possible to make them degorge enough to produce their own liquid. If you can do without brine, do it, because adding water will dilute the flavors.

Less brine = more taste

If you want to make vegetables in brine, add the vegetables in the container, then prepare a brine by mixing water + salt and pour the brine into the jar.

Note that if you want to make a 2% salt vegetable lacto, then you will have to make a 4% brine, as the salt will dilute in the vegetables (these being unsalted).

Container choice

There are a lot of choices, so here are some examples:

  • Mason jar: Very widely used container because it is very accessible and affordable, however this type of container is not suitable because it tolerates poorly the pressure and acidity of a lacto (the lid will rust). If you only have this on hand, it will work, but be careful of the pressure and think about changing the lid.
  • Glass jar with rubber: These jars are very good.
  • Crazy Korean Cooking: Very good value for money. Perfect for making medium, or large recipes and inside lid very convenient to limit the presence of oxygen.
  • Preserving crock: Best choice if you don't want plastic, and want to make large recipe. All crock come with a weight and sometimes they are equipped with a lid with water (air-lock effect).
  • Vacuum bag: Very convenient for a restaurant, for small portions, or for testing recipes. No oxygen guaranteed!

What weight to use?

Glass weigth

Anything is possible, but here are some ideas:

  • Leaf of cabbage, with a piece of the heart will make a very good weight that will make both pressure on the lid and the vegetables, keeping the latter under the liquid. The leaf may not ferment well, so it will probably go to the compost.
  • Glass weights: Inert, therefore very durable and healthy.
  • Rock: We strongly advise against it, unless you are certain that your rock will withstand Lactic Acid... You don't want to open your jar and discover that your rock is also fermenting... If you are certain of what you are doing, then it can be a good option, but think well about sterilizing your rock.
  • Ceramic weight: Super technique used so for thousands of years!
  • Plastic counter weight: Viscodisc are super practical; Especially for brines fermented vegetables.
  • Zip-lock bag filled with water: works relatively well.


Can we put fruit or spices?

Yes! Fruits and spices can add delicious flavors. Do not put too much fruit, because otherwise you will attract the yeasts that want to produce alcohol. There are no limits in the kinds of spices to use. The fermented carrots with a slice of orange is fabulous.

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