What is Lacto-Fermentation?
The “lacto” in the name refers to the bacteria Lactobacillus. Lactobacillus bacteria can convert sugars into lactic acid through a naturally occurring fermentation process. Lactic acid is a natural preservative that inhibits the growth of harmful or putrefying bacteria. Lactic acid also promotes the growth of healthy bacteria in the intestinal tract. That is why lacto-fermented foods are considered probiotic foods. As well as the preservation advantages, lacto-fermentation also increases vitamin and enzyme levels, as well as digestibility, of the fermented food, as well as producing antibiotic and anticarcinogenic substances that may contribute to good health.
Lacto-fermented pickles are not to be confused with many of the pickles that are available to buy commercially – these are done with vinegar, which offers more predictable results, but no lactic acid.
The science part is simple:
lactobacillus + sugar + salt – oxygen + time = lactic-acid fermentation.
Lactobacillus can come from a prepared culture, fresh whey, or be naturally occurring.
Sugar is naturally present in vegetables and fruit.
Salt inhibits the growth of undesirable microorganisms and helps keep vegetables crisp.
Oxygen is limited to enable the anaerobic process, stopping oxidation and the growth of unwanted bacteria.
Time taken to ferment can vary from a few hours to a couple months or more. The temperature of the environment where fermentation occurs will affect the length of time.
The idea is harder for some
Because we have spent decades in the mindset that organisms are bad and pasteurization is good, wrapping our head around the concept of fermentation in the first place is half the battle. At its very basic level, fermentation is controlled decomposition. Instead of allowing food to go straight to spoilage we introduce a preservation element such as salt, whey, or a starter culture. This directs food towards fermentation rather than rot.
The rest is art!
There is some flexibility in almost all the lacto fermentation rules. It is even possible to do a salt-free fermentation, though the results will be less storable and less crisp. As you progress you will develop methods and ratios that suit you.
- a knife and board for shredding your vegetables
- a large container for pounding
- a non-metallic fermenting vessel
- a weight
- your chosen vegetables
- filtered water (try not to use tap water that includes chlorine or fluoride as these can impede fermentation)
- unrefined salt (Himalayan rock salt is good, unrefined sea salt can be used but may include mold spores, table salt should not be used as the iodine present inhibits the process, you can also get pickling salt)
- optional: starter culture (this is not needed but can kick start the fermentation process by adding bacteria to get things going more quickly; see more in the ‘in depth’ section below.)
These are the basic steps that will be adjusted according to your recipe
- finely chop your chosen produce
- pound vegetables with salt to produce brine, or, make brine and add to vegetables
- place in fermentation container, ensuring vegetables are completely submerged in brine, and there is an inch or two of space before the lid.
- Wait patiently while fermentation happens.
Understanding the factors that influence fermentation will make it easier to decide how to get delicious, probiotic-rich ferments and help you avoid early mistakes.
There are many options for fermenting vessels, glass and ceramic are most common. Do not ferment in metallic containers as they react with salt and the acids produced during fermentation, plastic is also discouraged as it can harbor foreign bacteria more easily. Using cloth covers, tight lids, or lids with airlocks is a matter of personal preference. The important thing is to stop oxygen contact but still allow gasses to escape.
– Allowing oxygen in encourages the growth of unwanted bacterias which can result in mold, slime, and other problems that can mean having to dispose of your ferment.
– If you don’t allow the gasses that are produced during the fermenting process to release, pressure can build up and result in cracked or even exploding containers. If your vessel doesn’t allow gas to escape, you will need to open it regularly.
Even when using a lid with airlock, keeping the vegetables submerged under the brine during fermentation is important. There are many ways to do this from specialised weights to a cabbage leaf. Just ensure your fermenting vegetables are completely covered with brine and have an inch or two of space in the top of the fermentation container.
Vegetables ferment better under the protection of salt dissolved in water: brine. You can ferment any number of vegetables through two techniques: self-brine or added brine.
Self-brined Fermented Vegetables
Vegetables that are fresh and have not been dried out can actually create their own brine when salt is introduced. The salt naturally draws the water out of vegetables, thereby creating a natural brine. The main thing to keep in mind when making a self-brined fermented vegetable is that the vegetables have to be shredded into very fine pieces. The increased surface area that is created by grating or very finely slicing vegetables allows the salt to penetrate the vegetable and draw out large amounts of liquid. Examples of this type of fermented vegetable include sauerkraut, grated carrots and ginger, or a grated zucchini relish.
Added-brine Fermented Vegetables
Not every vegetable shines when it is finely diced or shredded. Many vegetables, like cucumbers, cry out to be left whole or in larger chunks. If you simply added salt to these large pieces of vegetables there is no way they could produce enough liquid to keep them submerged underneath the brine. So you must create a separate salt brine that you can pour over these larger vegetable chunks in order to keep the anaerobic environment necessary for the lactic acid to proliferate.
This brine can be used to cover any number of vegetables: cucumbers, peppers, tomato chunks, celery, carrots, garlic, onions, and just about anything else you are picking from the garden or buying from the market. This method is often preferred because the preparation of the vegetables tends to go a lot faster.
Which type of fermented vegetable you choose to make is entirely up to your personal taste. By making a bit of both types of fermented vegetables you can experience a wide variety of textures and flavors. This can keep things exciting for those you serve them to and flexible for the home cook who wants to ferment whatever they have on hand.
Temperature and Time
As with most culturing, lacto-fermentation happens faster at warmer temperatures. It may seem tempting to speed up the process so you can enjoy your ferments sooner, but this isn’t as straightforward as it seems. Culturing is a complex process. A variety of microbes are involved, and they all prefer different temperatures so changing the temperature can change the end resulting taste. Usually, ferments are kept at desired temperatures and then transferred to a cold environment to significantly slow fermenting when the desired flavor has been reached.
Experts generally recommend a slow, cool ferment at temperatures as low as 50°F (10°C). At temperatures this low, the process can take as long as 6 months or more, which is longer than many people want to wait.
Fermenting at 60-70°F (15-20°C) is slow enough to develop many of the complex flavors and retain good texture, and fast enough to enjoy your ferments within 2-6 weeks. A cooler, slower fermentation seems to last longer in cold storage as well.
When fermenting at above 70°F (20°C) fermentation happens as quickly as a few days. The bacteria that feed on pectin are more active, causing vegetables to break down into softer textures. The flavor is sharper, rather than tangy. Water evaporates faster, so be sure to monitor the level of brine in the vessel. When moved to cold storage, the ferments may not last as long.
As vegetables ferment, the bacteria feed on sugars in the produce. The breakdown of the sugars changes the flavor from sweet to tangy and tart. The process doesn’t have a standard timeline. There is a lot of debate over appropriate fermentation times, but only way to really know if your ferment is ready is to try it. The best time to move your ferment to cold storage is when it tastes right to you, after all, you are the one who will eat it so make it to your taste.
For example: Garlic starts with its usual bite, becoming intensely hot after a week or two of fermentation, then mellowing and becoming creamy to almost sweet. Cabbage develops a tart flavor and a sharp crunch. A long-fermented kraut becomes quite mellow and begins to soften.
There are a few different ways to prepare brine for fermenting vegetables. Choose the process that works best for you.
Historically, salt was used to preserve foods before refrigeration. Salt-only fermented vegetables are recommended for many reasons:
- Salt pulls out the moisture in food, denying bacteria the aqueous solution they need to live and grow.
- Salt allows the natural bacteria that exist on the vegetables to do the fermenting. Only the desired salt-tolerant Lactobacilli strains will live and propagate.
- By suppressing the growth of other bacteria and mold, salt provides a slower fermentation process that is perfect for cultured vegetables that are to be stored for longer periods of time.
- Salt hardens the pectins in the vegetables, leaving them crunchy and enhancing the flavor.
- Use 1-3 tablespoons of salt per quart of water to prepare brine for fermenting vegetables.
The more salt you use, the slower the fermentation process and the saltier the taste. Excessive use of salt can halt the culturing process by killing virtually all the microorganisms. A general guideline is around 2% salt.
While it is possible, it will usually produce a mushy result, which doesn’t store for very long.
- Salt-free ferments are often more bio-diverse, which can result mold.
- For a salt-free ferment celery juice or seaweed may be substituted, but they will not prevent a mushy texture.
- Some herbal seeds can be used in place of salt.
- Some freeze-dried starter cultures may be used on their own, without salt (see below).
Fermentation starter cultures
Starter Cultures Using some form of bacterial starter can speed up the fermentation process. Below are various starters that you might like to try. While unnecessary, the following starter cultures may be used in addition to salt, if desired. Many people find that the type of starter they use affects the flavor so try various types to see which ones your taste buds prefer.
- Whey: infuses the vegetables with good bacteria but is dairy-based so may not work for everyone. Make sure the whey is properly strained and fresh-tasting, as it will lend its flavor to the batch. Add salt along with the whey for flavor and to keep the vegetables crunchy. Using whey without any salt will make the ferment go faster but the end product will have a mushy texture and be more susceptible to mold.
- Kefir Grains: You can add milk or water kefir grains to your vegetable ferments. Just mix them into the vegetables. Once your vegetables are fermented you can eat the grains along with your ferment or fish them out. Once milk kefir grains or water kefir grains have been used in a vegetable ferment, they normally won’t work again in a milk or sugar-based beverage so it is recommended to use new grains for each batch of fermented vegetables. Salt in these ferments is optional, and will slow the process but enhance flavor and crunch while offering some protection from mold.
- Other Fermented Liquids: Finished, unflavored water kefir or kombucha may be used as a starter culture for fermenting vegetables. Add about ¼ cup liquid per quart of vegetables.
- Brine from a Previous Ferment: The fermented vegetable juice from a previous batch can be added to a new batch as a starter. Add about ¼ cup brine per quart of vegetables. Salt will still be necessary if you want additional mold protection and a crunchy texture
- Freeze-Dried Starter Cultures: Vegetable Starter Cultures are dried bacteria, packaged in foil envelopes, that you can mix into your ferment. While it is not necessary to purchase a dried culture, this option does offer the most consistent results in terms of taste and bacteria contained in the finished product. Dried cultures are also compatible with salt for taste, crunch, and some mold protection. When using a freeze-dried starter culture, follow the instructions included with that culture. (note: generally contain dairy as a carrier agent for the culture. Though, when used in the proportions indicated by the packet instructions, the amount of dairy in the finished vegetable ferment is so small as to be below trace amounts.)