Frequently Asked Questions

Properly completed lactic acid vegetable fermentation is an exceptionally reliable food preservation process. But the key words are properly completed.

According to Dr. Fred Breidt Jr., a USDA microbiologist specializing in fermented and acidic foods, the scientific literature had never recorded a case of food poisoning from raw vegetables that had been properly fermented. That remarkable historical safety record helps explain why vegetable fermentation has been practiced for thousands of years.

For perspective, improperly processed home-canned foods are a documented source of botulism. A study of U.S. foodborne botulism cases from 2001 through 2017 identified 94 cases associated with home-canned foods. That is not a failure percentage for home canning, but it illustrates the importance of proper preservation methods.

Canning is not inherently unsafe. Every food preservation method depends on following its procedures correctly. Vegetable fermentation, however, is a remarkably forgiving process, with a long history of successful food preservation even before modern instruments and equipment existed.

So what does properly fermented mean?

It certainly doesn’t mean placing vegetables into an unsuitable container, adding an unmeasured amount of salt, and leaving everything in a corner hoping for the best.

For dependable results, these conditions matter:

• Raw, good-quality vegetables. Begin with fresh vegetables and clean hands, utensils, and equipment.
• The correct amount of salt, carefully measured. Salt helps inhibit undesirable microorganisms while favoring the lactic acid bacteria responsible for fermentation. Too little salt can compromise the process. Always follow the salt measurements in our instructions.
• A clean, properly sealing vessel, such as The Probiotic Jar. Our fermentation system is engineered with a secure lid and a one-way airlock, allowing fermentation gases to escape while preventing fresh outside air from entering. This is an important distinction between a controlled anaerobic fermentation system and containers that permit continuing oxygen exposure—even when those products are advertised as sealing systems. If their closures don’t maintain an effective seal, they do not function the same way.
• The correct temperature range. Temperature influences microbial activity, the progression of fermentation, and the quality of the finished vegetables. Follow the temperature recommendations in our Expanded Guide.
• Sufficient fermentation time. A bubbling jar is not an indication of a finished ferment. A bubbling jar is an indication that fermentation is active. Our process is designed to allow the progression of microbial activity and the production of lactic acid that preserves the vegetables. Don’t shorten fermentation simply because the vegetables begin bubbling or taste pleasantly sour after only a few days.

Why does acidity matter?

As lactic acid bacteria ferment the natural sugars in raw vegetables, they produce acids that lower the pH.

A pH below 4.6 is a widely recognized food-safety threshold for controlling Clostridium botulinum. Some food-safety authorities recommend reaching pH 4.1 or below for additional protection.

Every batch of vegetables we’ve tested after fermentation in The Probiotic Jar has measured far below this threshold.

The combination of correctly measured salt, proper temperature, adequate fermentation time, and a vessel that prevents new oxygen from entering provides the conditions for the progressive development of acidity.

For a more detailed explanation of what happens during fermentation, see What’s Happening in the Jar in our Expanded Guide.

CAUTION! This process is designed for raw vegetables.

The fermentation methods explained in our Probiotic Jar guides are specifically intended for raw vegetable fermentation.

Applying these instructions to other food categories introduces completely different microbiological risks and requires methods and controls that are not covered by our guides and processes.

Do not use our raw vegetable fermentation process for meat, fish, or cooked foods of any kind.

Fruit and dairy fermentation also require different methods and are not generally covered by our Probiotic Jar instructions. Additional education about dairy fermentation is available through FermentingSeminar.org.

How can I recognize a ferment that has gone wrong?

One common development in vegetable fermentation is a thin layer of surface yeast, often called kahm yeast. In its earliest stage, it may appear simply as a dulling of the liquid’s normally glossy surface. As it develops, it can become a more noticeable, flat, whitish film.

This surface yeast is generally not considered dangerous by itself, although it can produce unpleasant flavors and affect the quality of the ferment. It should not be confused with fuzzy or patchy mold.

Other important warning signs include:

• Putrid or rotten odors.
• Visible fuzzy mold or suspicious colored growth.
• Unusual slimy deterioration.

Discard a batch showing signs of spoilage rather than attempting to rescue it. When there is uncertainty about following a proper process for fermenting raw vegetables, measured acidity offers a more objective check.

The bottom line

Proper raw vegetable fermentation isn’t guesswork. It’s a controlled process built on good-quality ingredients, the right amount of salt, the correct temperature range, a properly functioning fermentation vessel, and adequate time.

That being said, vegetable fermentation has been successfully practiced for thousands of years, long before people understood the microbiology involved. Its natural ability to create an acidic environment helped make it one of humanity’s oldest and most enduring methods of preserving food. Modern knowledge and properly designed equipment allow us to manage this remarkably resilient process with much greater precision and consistency.

The Probiotic Jar was designed to provide that additional control, helping maintain the anaerobic environment throughout the fermentation process while allowing gases to escape.

Learn more: See Brine, Assembly, Light & Temperature, What’s Happening in the Jar, and Detecting Spoilage in our Expanded Guide to Anaerobic Fermentation.

We do not recommend adding whey to raw vegetable ferments. Vegetable starter cultures, however, can sometimes be useful.

Here’s why the distinction matters.

Why we don’t recommend whey

Raw vegetables naturally carry lactic acid bacteria that begin multiplying when the vegetables are prepared with the correct amount of salt and placed in the right fermentation environment.

Fermentation then progresses through a series of microbial stages, with different populations of bacteria becoming active as acidity increases.

The earliest stage is especially important because it establishes the conditions for the microorganisms that follow.

Adding whey introduces microorganisms associated with dairy fermentation rather than relying on the bacteria naturally present on the vegetables. It can also alter the starting acidity, influencing which microorganisms flourish first.

This will most likely alter or shorten the natural early progression of microbial activity, affecting the development of the finished ferment and its flavor.

Some people also report a dairy-like or slightly cheesy flavor when whey is added to vegetable ferments.

Our recommendation is simple: Leave out the whey. The Probiotic Jar is designed to support the natural progression of raw vegetable fermentation without adding dairy cultures.

When a vegetable starter culture might help

Vegetable starter cultures are different because they’re specifically selected to ferment vegetable sugars.

Fresh, good-quality vegetables generally contain the microorganisms needed for natural fermentation, so adding a starter is usually unnecessary.

However, when vegetable quality or microbial activity is less than ideal, a properly selected vegetable fermentation culture may help establish a stronger population of desirable lactic acid bacteria.

A starter is not a substitute for adequate salt, clean equipment, correct temperature, or appropriate fermentation time. It also cannot make spoiled or unsafe vegetables suitable for fermentation.

Although vegetable cultures can be useful in particular circumstances, we generally prefer allowing the natural bacterial succession to take place.

Why starter cultures are different for dairy

Dairy fermentation is another matter entirely.

Specific cultures are selected to produce specific dairy products. The organisms and fermentation conditions used for yogurt, for example, differ from those used to make cultured sour cream.

Those cultures are chosen for their ability to ferment dairy substrates and produce the characteristics of the intended finished food.

Our Probiotic Jar vegetable fermentation instructions do not cover dairy fermentation methods. Additional educational information is available at FermentingSeminar.org.

Learn more: See Brine, Light & Temperature, and What’s Happening in the Jar in our Expanded Guide to Anaerobic Fermentation for more information about fermentation’s microbial stages and temperature phases, where covered.

What to do right now: First, check the temperature where your jar is sitting. For Phase 1 of vegetable fermentation, we recommend maintaining a temperature of at least 68°F, with approximately 68–72°F being our preferred range.

Remember that your home’s temperature may fall considerably overnight. If your home is cool, look for a location that maintains a consistent temperature. The top of your refrigerator may be slightly warmer because of the heat it generates, but check the actual temperature rather than assuming.

Also, not all fermentation activity is immediately visible. Gas can remain trapped among the vegetables rather than appearing as obvious bubbles in the airlock. You can gently rotate the jar back and forth, without lifting or disturbing the airlock, to see whether trapped bubbles rise.

Why it matters: Cooler temperatures slow fermentation and affect which microorganisms are most active. Temperature also influences the flavor of your finished vegetables. Maintaining the recommended range helps establish the conditions we want for the initial fermentation phase.

Learn more: See Light & Temperature in our Expanded Guide.

What to do right now: If your ferment has already been underway for 36 hours, leave the jar closed and allow fermentation to continue, provided the airlock remains functional. Our standard recommendation is to avoid opening the jar during the first 72 hours.

To keep the juices from running everywhere, put the Probiotic Jar in a shallow pan or on a cookie sheet.

If an adjustment is needed very soon after packing and sealing the jar, the first one to two hours are the best time to make that correction. Between two and six hours, opening becomes increasingly undesirable. After six hours, avoid opening the jar unnecessarily until at least 72 hours have passed.

Once the initial 72 hours have passed, if the vegetables need to be pressed back down:

• Thoroughly clean your working area and equipment.
• Wear clean, food-safe disposable gloves.
• Open the jar and press the vegetables firmly and evenly, repeatedly, beneath their existing juices.
• Reposition the brine bowl and reassemble the jar according to its instructions.

Don’t add fresh brine. In a vigorous sauerkraut ferment, gas trapped in the shredded cabbage can cause the vegetables to rise dramatically and push liquid out through the airlock. Firmly pressing the cabbage back down will often release trapped gas and reveal additional liquid that has been drawn from the vegetables.

Why it matters: Opening a ferment introduces outside air and opportunities for contamination. Allowing the initial fermentation process to progress without unnecessary interruption helps maintain the environment established inside the jar.

Learn more: See Assembly, Pack the Jar, and What’s Happening in the Jar in our Expanded Guide.

What to do right now: The timing matters.

• Within the first one to two hours: Open the jar and install the brine bowl using thoroughly clean equipment and food-safe gloves.
• Between two and six hours: Opening becomes increasingly undesirable as fermentation progresses.
• After six hours: Avoid opening the jar to install the missing brine bowl. The ferment will proceed best at this point if the brine bowl is simply left out.

Don’t repeatedly open and close the jar to make adjustments.

Why it matters: The brine bowl helps keep the vegetables submerged beneath their juices as gas is produced and the contents rise. This is particularly important with shredded cabbage and other vegetables that expand during active fermentation.

Learn more: See the Quick Start Guide, Assembly in the Expanded Guide, and Probiotic Jar Use and Care.

What to do right now: First, determine where the moisture is coming from. What looks like a leaking jar is often brine that has overflowed through the airlock and run down the outside of the glass. Condensation can also make the jar appear wet.

Check these four things:

• Look for overflow. Is there evidence that brine escaped through the airlock and ran down the outside of the jar?
• Check for condensation. Could the moisture simply be collecting on the outside of the glass?
• Check the white lid gasket. This is the white ring fitted to the lid—not the grommet holding the airlock. Is the gasket present and properly seated all the way around the lid? Ensure the gasket and jar rim are free of debris.
• Inspect the glass. Look carefully for visible cracks or damage.

If the gasket is missing or not seated properly, liquid may escape around the lid rather than through the airlock.

If this is the case, open the jar, seat the gasket properly, and reseal the jar. With the seal not having been secure during the early fermentation period, successful fermentation is less certain. But it’s worth waiting it out.

Why it matters: The Probiotic Jar relies on its carefully engineered lid and gasket to maintain its seal. A missing or incorrectly seated gasket can compromise that seal, while overflow or condensation may simply make the jar appear to be leaking.

If you find cracked glass, discontinue using that jar. If the jar is newly purchased and this is your first ferment, please contact customer service.

Learn more: See Probiotic Jar Use and Care and Assembly in the Expanded Guide.

What to do right now: Make room in your refrigerator for the complete jar, including the airlock. Move a shelf or rearrange other items if necessary.

Do not remove the airlock simply to make the jar shorter.

Why it matters: Moving the jar into the refrigerator slows fermentation, but it does not stop it immediately. The vegetables may continue producing gases during cold storage.

The airlock allows those gases to escape while preventing outside air from entering. Removing it changes the storage conditions that the Probiotic Jar system was designed to maintain.

Keep the airlock installed and properly maintained during this stage.

Learn more: See Handling Finished Ferments in the Expanded Guide.

Fermentation continues at a much slower rate under refrigeration, and gases may still be produced. If those gases cannot escape, pressure can build inside the jar. Although jar breakage from pressure buildup is uncommon, it is possible and can cause injury.

For this reason, we recommend leaving the airlock in place throughout refrigerated storage.

In certain circumstances, such as when a refrigerated ferment is opened and used every day, replacing the airlock with a stopper may be a reasonable option. Daily opening allows accumulated gas to escape and reduces the opportunity for significant pressure buildup.

However, if the jar remains sealed with a stopper for an extended or unpredictable period, pressure can accumulate. A stopper should never be assumed to provide pressure relief or protection against jar breakage.

A note about carbonation: The stopper should not be used to deliberately trap fermentation gases and create carbonation in the Probiotic Jar. Excessive pressure can break glass and cause serious injury. If you want to carbonate a finished beverage, use a bottle specifically designed for carbonation, recognizing that even pressure-rated bottles can fail if pressure becomes excessive.

Learn more about actual incidents of exploding glass:

• Exploding Beer Bottles — Root Simple
• Kombucha Bottle Explosion — 7NEWS

Shipping glass is expensive! We carefully double-box our glass jars to help protect them from breakage during transit.

As a small family business, we don’t enjoy the deeply discounted shipping rates available to some major retailers. We pay actual shipping costs, and those expenses are reflected in our shipping charges.

There is an excellent way to save money!

Purchase our Probiotic Jar Lid Kit, which ships free within the United States, and purchase a genuine Bormioli Rocco Fido glass jar separately.

Bormioli Rocco Fido jars are available through retailers such as Amazon, The Container Store, Target, and the Bormioli Rocco USA online store. Depending on the retailer, order size, and available customer benefits, you may qualify for free or reduced-cost shipping.

Our Lid Kit provides the components needed to convert a compatible Fido jar into a Probiotic Jar fermentation system.

Important: The jar must be a genuine Bormioli Rocco Fido jar in a compatible size. Other brands—even those that appear nearly identical—may not fit or seal correctly.

We’re delighted to help you save on shipping while enjoying the benefits of The Probiotic Jar.

Learn more: See the Probiotic Jar Lid Kit product listing and Shipping & Returns.

No. Our Lid Kit is designed exclusively for genuine Bormioli Rocco Fido jars.

The Probiotic Jar lid replaces the original lid on the compatible Fido jar, using its existing closure system.

Even when another manufacturer’s jar appears virtually identical, small differences in the rim, dimensions, and closure geometry can prevent our lid from fitting and sealing correctly.

Compatible sizes range from 500 mL through 5 liters.

Please verify the brand and size before ordering. A similar-looking jar from another manufacturer is not an acceptable substitute.

Learn more: See the Probiotic Jar Lid Kit product listing.

Yes! When ordering the Probiotic Jar Lid Kit, simply include a note with your order requesting the lid only, without the brine bowl or airlock.

We’ll honor your request and omit those accessories.

The Lid Kit price remains the same, whether or not you choose to receive the accompanying accessories.

Replacement bail wires are currently out of stock, and we do not anticipate having them available again in the near future.

These parts tend to sell out very quickly when available.

Please check the product listing periodically for updated availability.