Lacto-Fermentation: How to Ferment Fruits and Vegetables (2024)

What is Lacto-Fermentation?

Fermentation, or more precisely lacto-fermentation, involves submerging vegetables and fruits in a brine solution (salt and water) or salting them enough to release their own water and create their own brine.

Lacto-Fermentation Recipes

Looking to jump right in, here are some recipes you can try now:

• Shattah (fermented Middle Eastern Chile Paste)
• Fermented Hot Sauce
• Fermented Cabbage
• Fermented Cucumbers (Dill Pickle)
• Lacto-Fermented Radishes
• Lacto-Fermented carrots
• Red Cabbage Sauerkraut
• Fermented Jalapenos
• Fermented Lemons
• Fermented Tomatoes
• Fermented Celery
• Sambal Oelek (Indonesian chili paste)
• Korean Radish Kimchi
• Fermented Beets
• Fermented Pineapple Jalapeno Hot Sauce
• Fermented Mango Habanero Hot Sauce
• Fermented Passion Fruit Habanero Hot Sauce

Lacto-Fermentation vs Pickling

Pickling refers to the process of preserving fruits and vegetables in a vinegar solution. Examples include pickled ginger, pickled green tomatoes, pickled cherry tomatoes, pickled turnips, and green beans.

Use Fresh Ingredients

Using fresh (or homegrown garden) produce is crucial when fermenting for several reasons:

1. Nutrient Content: Fresh vegetables are rich in nutrients, including vitamins and minerals. These nutrients are essential for the growth of beneficial bacteria during the fermentation process. Fermentation enhances the bioavailability of these nutrients, making them easier for your body to absorb.
2. Texture: Fresh vegetables have a crisp texture, which is often desirable in fermented foods. Overripe or wilted vegetables lack the firmness needed for a good texture in the final product.
3. Enzymes: Fresh vegetables contain natural enzymes that play a role in the fermentation process. Enzymes help break down complex molecules into simpler ones, aiding in the production of desirable compounds and flavors during fermentation.
4. Water Content: Fresh vegetables have higher water content, which is important for creating the brine necessary for fermentation. The natural juices from fresh vegetables contribute to the brine, providing the necessary environment for beneficial bacteria to thrive.
5. Microbial Diversity: Fresh vegetables carry a diverse population of naturally occurring beneficial bacteria. These microbes contribute to the unique flavors of fermented foods. Using fresh vegetables ensures that you introduce a variety of beneficial strains into your ferment.
6. Safety: Fresh vegetables are less likely to be contaminated with harmful bacteria. Using wilted or spoiled vegetables increases the risk of introducing harmful microorganisms into the ferment, leading to spoilage or foodborne illnesses.
7. Aroma and Flavor: Fresh vegetables have a vibrant aroma and flavor, which can significantly enhance the taste of the final fermented product. Overripe or spoiled vegetables can impart off-flavors to the ferment.

The Importance of Salt and How Much to Add

Salt plays a crucial role in the process of fermentation for several reasons:

1. Osmotic Regulation: Salt helps to control the osmotic pressure in the fermenting environment. When salt is added to vegetables or fruits, it draws out moisture through osmosis. This process helps to create a brine (salty liquid) that submerges the food being fermented. The salt in the brine prevents harmful bacteria and molds from growing, creating a favorable environment for beneficial bacteria like Lactobacillus to thrive.
2. Preservation: Salt acts as a natural preservative. It inhibits the growth of spoilage-causing bacteria and pathogens, allowing the beneficial lactic acid bacteria to dominate the fermentation process. This preservation effect helps extend the shelf life of the fermented food.
3. Texture and Firmness: Salt affects the texture of the fermented product. It helps maintain the crispness of vegetables by slowing down the enzymatic processes that lead to softening. This is especially important in vegetable ferments like sauerkraut and pickles, where a desirable texture is crucial.
4. Flavor Enhancement: Salt enhances the natural flavors of the ingredients being fermented. It can suppress bitterness and enhance sweetness, making the final product more palatable.
5. Microbial Selection: Salt-tolerant bacteria, such as Lactobacillus species, are more resistant to the presence of salt compared to other harmful microorganisms. By adding salt, you encourage the growth of these beneficial bacteria, which are essential for the fermentation process.
6. Safety: Properly salting the fermentation environment helps to create a hostile environment for harmful bacteria like Clostridium botulinum, which can cause botulism. Ensuring the right salt concentration is crucial for food safety during fermentation.

Salt Ratio

As a general rule, the recommended amount of salt should be in the 2%– 4% range by weight. It's important to note that the right amount of salt is critical for successful fermentation. Too little salt can allow harmful bacteria to proliferate, while too much salt can inhibit the growth of beneficial bacteria.

Dry Salting

In vegetable fermentation, dry salting involves sprinkling salt directly onto the vegetables, which draws out moisture from the vegetables through osmosis. The salt helps to soften the vegetables and extract natural juices, creating a brine without the need for added water. The extracted brine then covers the vegetables, submerging them during the fermentation process.

When it comes to dry salting, I prefer to use a 2.25 to 2.5% ratio. Here’s how you can calculate the right amount of salt needed for your ferment:

1. Weigh Your Vegetables/Fruits: Let's say you have 600 grams of vegetables you want to ferment.
2. Calculate the Salt Percentage: For a moderate salt concentration, you can use 2.5% salt. To find out how much salt you need, multiply the weight of your vegetables by 0.025 (which represents 2.5%).

Submersion Salting (Salt Brine)

Submersion salting, or brining, is used when you are fermenting fruits and vegetables that do not have too much water content or if you’re fermenting them whole. This technique can be applied to hot peppers, garlic, carrots, and giardiniera mix.

Why You Should Prevent Oxygen from Entering Your Ferment

Oxygen exclusion is crucial in the fermentation process for several reasons:

1. Anaerobic Environment: Fermentation is an anaerobic process, meaning it occurs in the absence of oxygen. Certain microorganisms, like lactic acid bacteria, yeast, and other beneficial strains, thrive in environments without oxygen. These microorganisms break down sugars and other organic compounds to produce acids, alcohols, and gases, transforming the raw ingredients into fermented products like sauerkraut, kimchi, yogurt, and pickles.
2. Prevention of Spoilage: Oxygen promotes the growth of undesirable microorganisms, including molds, yeasts, and bacteria, which can spoil the food being fermented. By excluding oxygen, you create conditions that favor the growth of specific beneficial microbes, ensuring the fermentation process leads to safe and tasty products.
3. Inhibition of Oxidation: Fermentation can involve the enzymatic breakdown of various compounds within the food. Oxygen can cause oxidation, which alters the flavor, color, and nutritional content of the food. By keeping oxygen out, you preserve the natural qualities of the ingredients and maintain the desired characteristics of the final product.

Why You Should Let Carbon Dioxide Escape

Allowing carbon dioxide (CO2) to escape (degassing) during fermentation is essential for several reasons:

1. Preventing Pressure Buildup: Fermentation produces gases, primarily carbon dioxide. If these gases are not allowed to escape safely, they can build up pressure inside the fermentation container. This pressure can potentially lead to the container bursting or exploding, causing a mess and, more importantly, posing a safety risk.
2. Avoiding Contamination: Allowing gases, especially carbon dioxide, to escape helps create a one-way barrier against external contaminants. As CO2 exits, it helps to push away air from the surface of the fermenting food. This is important because exposure to air can introduce harmful bacteria, molds, and yeasts, which can spoil the ferment or pose health risks.
3. Maintaining Anaerobic Conditions: Fermentation is an anaerobic process, meaning it occurs in the absence of oxygen. Allowing CO2 to escape ensures that the fermentation environment remains anaerobic.
4. Preventing Off-Flavors: If CO2 is not allowed to escape, it can dissolve back into the liquid and form carbonic acid, which can create off-flavors in the fermented food. Allowing CO2 to escape helps prevent this acidification, contributing to the overall quality and taste of the final product.

Improving Flavor with Vinegar

Many fermentation recipes call for vinegar to be added at the end of the ferment. This is done primarily to improve flavor and extend shelf life. Some of our favorite fermented hot sauces (Frank's, Tabasco and others) have vinegar added to them. I like to add a dash of vinegar to all my hot pepper ferments, whether I'm making hot sauce or chili paste.

In order to ensure that oxygen doesn’t enter and that carbon dioxide has the ability to escape, there are a few things you can do:

• Use a fermentation airlock: This is essentially a lid with a valve that allows gasses to escape safely. It fits directly on to your jar. There are several options like the Klemon and Masontops (affiliate links).
• You can use a standard lid and unscrew it twice a day to let any built-up air escape and quickly reseal. This option is not ideal as it can allow oxygen back in.
• Vacuum Packing with bags. This is used in the restaurant industry quite heavily but the downside is that the CO2 is not released which could burst the bag or create off flavors in the ferment.

I only use specialized fermentation lids when making any ferment. They are the safest option. In order to keep the fruits and vegetables submerged, you will also need to use one of the following:

• Glass fermentation weight (affiliate link). They are versatile and can help extract water from a dry salted ferment)
• A ziplock bag filled with water, beans or marbles can also help keep the food submerged
• A small plate or bowl (like a sushi dipping bowl)

Ideal Fermentation Temperature

The ideal lacto-fermentation temperature typically falls within a range of 60°F to 75°F (15°C to 24°C). In other words, room temperature.

Fermentation Time

The time it takes to lacto-ferment food can vary widely based on several factors, including the type of food being fermented, the ambient temperature, the desired level of fermentation, and personal preference for taste and texture. Generally, the process of lacto-fermentation can take anywhere from a few days to several weeks.

Is My Ferment Ready?

There are a few telltale signs to look out for when you’re trying to determine if your lacto-fermented vegetables are ready:

• Smell: Fermentation often produces distinct, sometimes tangy or sour smells. If the fermenting food has a pleasant, slightly tangy aroma, it's likely ready. If it smells off, it might not be ready yet or could be spoiled.
• Taste: Take a small sample and taste it. If it has the desired flavor, texture, and level of sourness, it's ready. For example, in vegetable ferments like sauerkraut, the cabbage should taste tangy and slightly crunchy.
• Texture: Some ferments, like pickles, should maintain a certain crunch. Over-fermented pickles might become mushy. Check the texture to ensure it's still appealing.
• Bubbling: Many ferments produce bubbles as a result of the fermentation process. Bubbles indicate that the ferment is active. However, the absence of bubbles doesn’t necessarily mean the ferment isn't ready, as some ferments can proceed without visible bubbling.
• Color: The color of the ferment might change during the process. For instance, vegetables might change from vibrant to a slightly subdued hue. However, drastic color changes could be a sign of spoilage, so use your judgment.

My Ferment is Ready, Now What?

You have a few options. First off you can remove the fermentation lid and weights. You can use a standard lid and refrigerate your ferment as is.

Will fermentation continue in the fridge?

Lacto-fermentation does continue in the fridge, but at a much slower rate. When you transfer a lacto-fermented product to the refrigerator, the cold temperature slows down the fermentation process significantly. The cold environment doesn't stop the fermentation entirely, but it greatly reduces the activity of the lactic acid bacteria and other microorganisms involved in the fermentation process.

Common Concerns

Fermentation is still misunderstood and feared by many people. Here are the two most common visual concerns people have with their ferments.

Kahm Yeast

Kahm yeast is a type of wild yeast that can develop on the surface of lacto-fermenting foods. It appears as a thin, white to cream-colored layer, resembling a wrinkled skin, on the surface of the fermenting liquid or on top of vegetables in brine. Kahm yeast is a common occurrence in home fermentation, particularly when the fermentation environment is not well-controlled.

While Kahm yeast is not harmful, it's generally considered undesirable in fermentations for several reasons:

1. Flavor Alteration: Kahm yeast can alter the flavor of the ferment, sometimes resulting in off-putting or unpleasant tastes.
2. Texture Changes: Fermented foods with Kahm yeast might develop an undesirable texture, often described as slimy or rubbery.
3. Nutrient Competition: Kahm yeast competes with desirable lactic acid bacteria for nutrients. This can slow down the fermentation process and affect the growth of beneficial bacteria that contribute to the desired flavors and preservation of the food.

To prevent Kahm yeast formation:

1. Use Proper Equipment: Ensure your fermentation equipment (jars, lids, weights) is clean and sanitized to minimize the introduction of unwanted microorganisms.
2. Submerge Ingredients: Keep solid ingredients submerged in the brine or liquid to minimize exposure to air, which can help reduce the chances of Kahm yeast forming on the surface.
3. Maintain Consistent Temperatures: Ferment at the appropriate temperature recommended for the specific food you're fermenting. Proper temperature control can encourage the growth of beneficial lactic acid bacteria over unwanted organisms like Kahm yeast.
4. Use an Airlock: If you're fermenting in an open container, consider using an airlock. An airlock allows gases to escape but prevents outside air (and potential contaminants) from getting in.

Cloudy Brine

A cloudy brine in fermentation is a common occurrence and usually not a cause for concern. There are several reasons why the brine in your fermentation might appear cloudy:

1. Microbial Activity: During fermentation, beneficial bacteria (such as lactic acid bacteria) consume sugars and other compounds in vegetables or fruits. As a result, they produce lactic acid and other by-products. These by-products can sometimes cause the brine to appear cloudy.
2. Yeast Activity: Wild yeasts naturally present on the vegetables or in the environment can also contribute to cloudiness. Yeast cells are microscopic and can be suspended in the brine, causing it to look cloudy.
3. Starches and Proteins: Vegetables often contain starches and proteins. During fermentation, these compounds can break down into smaller particles, which may scatter light and create a cloudy appearance in the brine.
4. Minerals and Salts: Minerals and salts in the vegetables can dissolve in the brine, contributing to cloudiness. This is especially common if you're using unrefined sea salt, which contains minerals that can affect the appearance of the brine.
5. Lactic Acid Bacteria: The proliferation of lactic acid bacteria, which are desirable in most vegetable ferments, can cause cloudiness. These bacteria can form colonies and create a milky appearance in the brine.

While cloudiness is generally harmless, there are a few things to watch out for:

• Unusual Odors: If the cloudy brine is accompanied by a foul or unpleasant odor, it could be a sign of spoilage.
• Mold: If you see signs of mold on the surface of the brine or on the vegetables, discard the batch. Mold is a definite indication of spoilage.
• Slimy Texture: If the vegetables feel excessively slimy to the touch, the ferment may be spoiled, and it's best to discard it.

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