How to Make Fermented Vegetables (Lacto-Fermentation)
This article aims to give you a basic understanding of how to make fermented vegetables at home. You’ll see how easy it is to make!
Skip to the section:
- What Is Lacto-Fermentation?
- How to Make a Vegetable Fermentation
- Which Vegetables?
- How Much Salt To Add?
- Keeping the Oxygen Out
- Letting the CO₂ Out
- Optimal Temperature
- Fermentation Length
- Choosing a Vessel
What Is Lacto-Fermentation?
A lacto-fermentation is generally a salt-based vegetables fermentation.
This type of fermentation is called lacto-fermentation, or lactic acid fermentation because of the role the Lactic Acid Bacteria (LAB) play in it.
Among all the lactic fermentation recipes, there is sauerkraut, kimchi, pickles and olives, but also milk-based products (yogurt, kefir, cheese…) and meat-based (dry sausage). This article will concentrate on fermented vegetables.
If you want to jump ahead, here are 3 Foolproof Fermented Vegetbles Recipes!
How to Make a Vegetable Fermentation
Every recipe could be boiled down to this formula:
INGREDIENT + SALT ‒ OXYGEN
To induce a lacto-fermentation, we add salt to vegetables, and limit the contact with oxygen.
This creates an ideal environment for the development of good bacteria (lactic acid bacteria), which will repel undesirable microorganisms.
The result? Vegetables that are perfectly safe to eat, with a delicious tangy taste. Yum!
Fermenting vegetables can be summarized in 5 easy steps:
- Cut up your vegetables.
- Mix with salt.
- Let ferment at room temperature.
- Limit oxygen presence.
- Wait a few days, or a few months, and enjoy!
Vegetable fermentation is simpler than it looks. You can start right away with the vegetables you have on hands! The many benefits of lacto-fermentation are just within reach.
If you’re a visual kind of person, check out this infographic about fermented vegetables!
Are you the kind of person who wants to know everything in detail before starting? We invite you to read on.
Ingredients of a Lacto-Fermentation
A lacto-fermentation has these basic ingredients:
- Water (only if the vegetables do not produce enough liquid, and you need to make brine)
If a vegetable (or fruit) 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 live on the skin of vegetables. Without these bacteria, no fermentation!
You can start with easy vegetables such as cabbage, carrots, pickles and beets.
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 you want to speed up the fermentation process, or if you want to do it in a more controlled environment, there are two techniques:
- Add a lactic acid bacteria for vegetables culture.
- Add brine from one of your previous jars of fermented vegetables (this liquid is full of lactic acid bacteria).
Salt plays an important role in the fermentation of vegetables.
On the one hand, it helps to start the fermentation process by promoting the development of good bacteria, while limiting the development of undesirable microorganisms. On the other hand, it helps to preserve the texture of the vegetables.
The important thing when choosing your salt is that the only ingredient is “salt”.
To know which salt to choose for your fermentation, look at the ingredients: it must be free of iodine and anticaking agents. Iodine hinders fermentation while anti-caking agents can disrupt the taste.
The important thing, when you choose your salt, is that the only ingredient is “salt”.
You can use sea salt or mine salt (pink salt, white salt, etc.).
See all our tips in Which salt to choose for fermentation
How Much Salt to Add?
Adding 2% of the weight of the vegetables in salt is usually adequate.
If there is not enough salt, the fermentation will not work. The more salt there is, the slower the fermentation will be and the longer the vegetables will stay crunchy. However, if you use too much salt, the fermentation will be inedible!
Aim for 2% of the weight of vegetables in salt for lacto-fermentation consumed in less than 3 months. For lacto-fermentations that you want to keep for more than 6 months, 4% salt is suitable. In any case, never use less than 1%.
See How much salt for fermentations for more information.
There are two ways to add salt:
Dry Salting (Sauerkraut Style)
Adding salt to vegetables is necessary for fermentation.
Dry salting will be used when vegetables can release liquid after being pressed (cabbage, carrots, onions…).
The percentage of salt applies to the weight of the vegetables. For example, for a 2% sauerkraut recipe, weigh your cabbage and add 2% salt based on that weight.
Weigh the vegetables + add 2% of this weight in salt
For example, if you have 1000g of cabbage, you will need 20g of salt (1000 x 2%).
Brine (pickle style)
Brine will be used when the vegetables used cannot produce their own liquid, for example when you want to ferment whole or large pieces of vegetables.
There are two ways to calculate the amount of salt to add to the brine:
- Based on the volume of the container
- Based on volume/weight of water
Volume of the container
If you plan to fill the container completely, just take its volume as a base and apply the percentage of salt.
Example: To make carrots with 3% salt in a 1-litre jar, add 30g of salt (1000ml x 3% = 30), then put as many vegetables as you want in the jar. Finish by adding water until the jar is full.
Here, we rely on the volume of the jar. The salt is added and then submerged in water to dilute.
Volume/weight of water
You can also calculate the percentage of salt added to the water. For this technique, a higher percentage of salt (usually 3 or 4%) should be added, as vegetables are not included in the calculation. However, the vegetables will absorb some of the salt, and the result will be similar to the first technique after a few weeks.
Example: to make vegetables with 4% salt in 1 litre of water, add 40g of salt (1000g x 4% = 40g) to the water and mix to dilute. This brine should be added to the (unsalted) vegetables previously put in a jar.
A little trick to make calculations easier: 1 litre of water is equal to 1 kg (1000 g) of water.
For more details, see our article on salt and brine in lacto-fermentation.
Water is used only if you make vegetables in brine (see previous section). 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.
Parameters of a Good Fermentation
Keeping the Oxygen Out
A lacto-fermentation is an anaerobic fermentation, which means that it does not require oxygen. Lactic acid bacteria are the only ones that can grow in a salty, acidic and, above all, oxygen-free environment.
On the contrary, if oxygen enters your jar, moulds and yeast could settle, making the preparation unfit for consumption.
If you want to make a super good lacto-fermentation without mould, you need a strategy to limit the presence of oxygen!
When you compress vegetables in a jar with salt (see section “Dry Salting”), the salt will naturally make the water come out of the vegetables.
This natural brine will submerge the vegetables, creating an oxygen-free environment. If you add brine (see section “Brine”), it should submerge the vegetables.
Keeping the vegetables submerged is the most important part of vegetable fermentation.
To keep the vegetables submerged, a weight or counterweight is usually used which is placed on the surface of the vegetables to be fermented.
There are several things that can be used as weights:
- Ziploc-style plastic bag filled with water, marbles, etc.
- Glass weights
- ViscoDisc canning inserts
- Shooter glass, small plate, etc.
- Ceramic fermentation weights
If possible, choose food-grade plastic or glass. Acidity and salt may degrade some metals and minerals, such as rocks.
Letting the CO₂ Out
Once we put the vegetables into jars, we screw the lid on. Fermentation will create carbon dioxide gas (CO₂). This is normal, but we don’t want our jar to explode! So we want to let it out.
To evacuate the CO₂ (without letting oxygen in) several options are available:
- Use an airlock: allows the CO₂ to go out while preventing the air from coming in. Very practical for any recipe volume – it fits a Mason jar as well as a 50-litre boiler.
- Leave the lid unscrewed (¼ of a turn) for the first week, then put in the fridge.
- Slightly unscrew the lids once or twice a day to let the gas out (burping).
- Use hinged-lid jars (such as Le Parfait): these pots degas themselves due to the rubber joint.
- Vacuum-packing: very practical technique for making small portions.
If you open your jar, then put it in the refrigerator to slow down the fermentation and avoid contamination.
Maintaining the Optimal 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.
In general, ambient temperatures are perfectly suited for home fermentation.
If you are not in a hurry and have access to a cold room, the ideal temperature for a long conservation is between 10 and 15°C (50 to 59°F).
In a refrigerator (between 0 and 4°C, or 32-40°F), fermentation will almost completely stop. It is therefore the ideal place to put your jar of half-consumed sauerkraut if you don’t want mould to develop.
The Right Fermentation Length
The length of fermentation depends… on your taste! The longer the fermentation, the more acidic and tender the vegetables will become.
Some people love vegetables that fermented for a very long time (several months), while others prefer to let their vegetables ferment for less than a week. All tastes are in nature!
The speed of fermentation depends on several factors:
- Temperature (hotter it is, faster is the fermentation)
- Size of the vegetables (smaller the pieces, slower the fermentation)
- Amount of salt (more salt = slower fermentation)
- Types of vegetables
Is this your first lacto-fermentation? Let it ferment for a week, then put it in the refrigerator.
By keeping the fermentation time short, you can get used to the taste of the fermented vegetables, and be less likely to fail your fermentation.
Choosing a Fermentation Vessel
There are many types of fermentation vessels. Here are some examples:
Mason Jar-style glass jars: popular, accessible and affordable. However, this type of container does not tolerate the pressure and acidity of lacto-fermentation, and the lid can rust over time. Several fermentation accessories are designed for these types of jars.
Le Parfait-style glass jars: these jars with a wire hinged-lid and rubber gasket are well suited. No special techniques are required to evacuate the CO₂, as it will be able to escape by itself through the gasket.
Crazy Korean Cooking fermentation jar: All-in-one jar with a very good price-performance ratio. Its inner lid is very practical to limit the presence of oxygen (and odours). Perfect for big recipes.
Ceramic jar: traditional method. The jars come with a weight and are sometimes equipped with a lid with a water gutter (airlock effect).
Vacuum-sealed bag: very practical for a restaurant, for small portions, or doing tests. Oxygen-free, guaranteed! It produces plastic waste, however.
See What equipment for my fermented vegetables for more details.
How Long Should I Ferment My Vegetables?
Vegetables can be left to ferment from a few days to several weeks. It depends on your taste!
In general, we recommend aiming for 7 days of fermentation, to begin with.
The longer the fermentation time, the more tender the vegetables will be and the more the flavours will develop. On the other hand, vegetables that have not been fermented for long will retain more of their crunch and have a more delicate taste.
Kimchi and pickles are often enjoyed after only a few days of fermentation at room temperature.
Sauerkraut and root vegetable recipes, on the other hand, need to be refined over time and are delicious after one or two months of fermentation. The taste of fermented garlic will change after one year of fermentation.
Can I Open My Jar During Fermentation?
We do not recommend opening jars during fermentation.
It exposes the content to air, and therefore to environmental microorganisms that could contaminate it. It is therefore advisable to place the jar in the refrigerator after opening it.
If you absolutely must open it and then want to continue the fermentation at room temperature, make sure everything is submerged under the brine before closing it. If necessary, add a little brine with 2% salt.
When to Remove the Weights?
You can remove the weights, inserts, and other accessories just before putting the jar in the fridge.
As long as the jar is at room temperature, we recommend leaving the weights in place to keep the vegetables submerged.
How Long Does Lacto-Fermentation Keep?
Fermented vegetables have a shelf life of several years at room temperature. However, their taste and texture continue to change over time.
Fermented vegetables should not have mould on the surface or a bad smell.
To find out how to keep them for a long time, see our article on preserving vegetables by fermentation.
How do I know if my fermentation is successful?
Successful lacto-fermentation is easy to identify:
- Tart and sometimes fizzy taste
- Slightly vinegary odor
- Brine that is sometimes cloudy
On the other hand, a failed lacto-fermentation will be easy to distinguish:
- Presence of green, white or blue mold on the surface
- Marked rotten odor.
To learn more, consult our Frequently Asked Questions about problems with vegetable fermentation.