So many questions.
If I open the jar to sample it, won’t that let in air and then mold will grow?
If I don’t see any bubbles, doesn’t that mean fermentation didn’t happen?
If it smells like bleach, should it be tossed?
Let me hold your hand through the process sharing fermentation signs, letting you know what to watch for and describing how a finished batch of sauerkraut should taste.
The friendly bacteria will be doing most of the work. Your job is to provide the right home for them.
Trust in the process. The wonderful Mighty Microbes really do know what to do.
The hardest part? Waiting seven days to first taste the transformation from salty cabbage to the tangy crunch of sauerkraut.
SET THE STAGE FOR SUCCESSFUL FERMENTATION
Your jar is now packed with freshly salted cabbage.
The lid is on.
Fermentation has already started.
LABEL YOUR ARTWORK
I like to label my jars using green or blue painter’s tape and a permanent marker. I like the “Painter’s Tape” because I can remove it later without leaving a sticky residue. Grab what you have and get marking. I note the flavor of sauerkraut I made and the date I started fermenting it. Believe me, a few weeks into the process, or months later, when you unearth the jar in your refrigerator, you’ll appreciate knowing what’s in the jar and when you made it.
And, it doesn’t hurt to make a few notes on anything specific you did for this particular batch. Some keep this in a separate notebook. Some just add more tape to the jar with extra notes.
PLACE YOUR JAR OF FERMENTING SAUERKRAUT IN A SHALLOW BOWL
Imagine entering your kitchen. It is one day into the fermentation process. You see brine oozing across your counter and dripping onto the floor…
Why did that happen?
The first set of Mighty Microbes to go to work for you are the gas producing Leuconostoc Mesenteroides. These bacteria do most of their work during the first 3-5 days, producing acids, alcohols and…
carbon dioxide (CO2), hence the bubbles you see rising to the surface.
However, the CO2 can get trapped within your packed sauerkraut, causing your fermenting mixture to move up in your jar, forcing precious brine to overflow, which is why you’ll want to place your jar of sauerkraut in a dish in order to prevent this brine making a mess on your counter. I’ll cover how to minimize brine overflow below.
FIND A SPOT WITHIN THE IDEAL TEMPERATURE RANGE FOR FERMENTATION
The ideal fermentation temperature range for producing sauerkraut with the most complex flavors is between 65 and 72°F (18–22°C). Fermenting within this temperature range allows the three bacteria strains necessary for fermentation to ferment your cabbage in the proper sequence. For example, the L. Mesenteroides mentioned above might not grow at temperatures higher than 72°F (22°C), which would be detrimental to the flavor of your sauerkraut.
Where your ambient room temperate is within this range will determine the rate at which fermentation happens. The lower the temperature, the slower the fermentation. The higher the temperature, the faster fermentation unfolds. Ideally, you want the temperature to be somewhat stable, not fluctuating more than 5°F (3°C) in either direction.
It doesn’t hurt to place a thermometer next to your jar to monitor what the temperature is that you’re fermenting at. Nothing to get overly concerned about, but helpful to know if your fermentation is not progressing as expected. The temperature you are fermenting at will help you decide how long to ferment. Some even use a min-max thermometer. It keeps track of what the highest and lowest temperature has been until you reset it. Quite handy.
It’s best to find a spot away from your stove or your refrigerator due to excess heat these appliances might generate.
Temperatures below 60°F (15-16°C) results in a slow and incomplete fermentation.
Temperatures above 80-85°F (27-29°C) can result in abnormal fermentation. Though not ideal, many do successfully ferment in hot weather. You’ll definitely want to shorten fermentation time and to achieve complex flavors in your sauerkraut, find a way to cool things down: 11 Cool Fermentation Tips for Hot Weather.
KEEP YOUR FERMENTING SAUERKRAUT OUT OF DIRECT SUNLIGHT
I like to be able to keep an eye on my ferments. There is so much to watch and learn from which is why fermenting in a glass jar is so practical. I keep all my ferments in my kitchen on the counter and out of direct sunlight, but still illuminated by indirect light.
The high levels of ultraviolet radiation in direct sunlight can destroy or inhibit the bacteria that will be working for us and can also diminish nutrients in the food that is being fermented. So, find a spot out of direct sunlight. If you are concerned about any light destroying the bacteria, feel free to cover your jar with a towel.
Some like to keep their ferments in kitchen cupboards. There is nothing wrong with this, just don’t forget them there in their little dark home, an easy thing to do.
ADJUST FERMENTATION LENGTH TO FERMENTATION TEMPERATURE
If your home environment is within the ideal temperature range of 65 to 72°F (18–22°C), 3-4 weeks is a good length of time to ferment your sauerkraut. This allows time for each of the three successive colonizations of hard-working bacteria involved in fermentation to perform their magic.
If your climate is exceptionally warm, the bacteria will progress through these stages much more rapidly and you may find 10 days to be plenty; taste at about Day 5. If your house is extra cool, it may take 4-6 weeks for your sauerkraut to fully develop; taste around Day 10.
Ideally, you are not opening your jar numerous times and disturbing the friendly, hard-working bacteria. However, it’s a learning process and tasting is a good way to learn. And it’s nice to know that by Day 7, the L Mesenteroides have typically produced enough lactic acid to protect it from outside invaders they may try to sneak in when opening your jar.
I further discuss adjusting the length of fermentation to your home environment and your taste buds below.
MAKE SURE YOUR SAUERKRAUT MIXTURE IS UNDER THE BRINE
The fermentation of sauerkraut is an anaerobic process. This means your mixture of sauerkraut needs to remain below the brine by using a fermentation weight of some sort. Even if you are using a lid with some type of airlock, your fermenting sauerkraut mixture still needs to be below the brine.
Most books and articles on fermentation – including myself – are quick to have you mix up additional brine and pour this into your jar of packed sauerkraut if there is not enough brine to cover it. A year or so ago, I found in my favorite fermentation book, Fermented Vegetables – reviewed here, that authors Kirsten and Christopher Shockey recommend against adding brine claiming doing so results in discoloration and mushy sauerkraut. This has been tickling my brain ever since and I’m slowly finding that adding fresh – or fermented brine – does negatively impact texture and flavor.
So, if you just packed your jar – or its only been 12-24 hours – and your sauerkraut is not under some brine – even a rather thin layer, see my suggestions in Dry Sauerkraut? 17 Transformative Tips [BONUS: Gut Shots Recipe] for ways to get more liquid into your jar.
NOTE: Tips #15 and #16 suggest adding brine during fermentation as a last resort. And, in Tip #17, I suggest adding fermented brine before storing your sauerkraut. The jury is not out yet, but I just started eating one of the jars I did that to last winter. I was not all happy with the results: mushy texture, watered-down flavors. Not what I was expecting.
TIPS TO MAXIMIZE PROBIOTIC COUNT
I don’t quite know where to put this, but I periodically am asked if there is a way to achieve maximum probiotic counts in a ferment. Without expensive lab tests by curious micro-biologists, we don’t know how what we do impacts actual numbers, but to maximize the working conditions for our Mighty Microbes, I suggest the following:
- Use high-quality ingredients. The greater the nutrition of the cabbage and vegetables used, the greater the level of nutrients for the bacteria that will be turning your salty cabbage into sour sauerkraut. This would also include your salt. A mineral-rich salt (Himalayan Pink or Redmond Real Salt) will contain more food for those Mighty Microbes than a processed salt containing only sodium chloride.
- Use fresh “winter” cabbage. Winter cabbages are planted in late summer and harvested in early fall, ideally after the first frost. These prized cabbages have tight heads, are harder, have thicker leaves and a higher moisture content than summer cabbages. You’re in luck if you, or a local farmer, can grow a variety of late cabbage especially suited for sauerkraut making (Krautman, Danish Ballhead and Premium Late Dutch). In addition, make your sauerkraut before the cabbage has been stored for months.
- Thinly slice cabbage. Cabbage sliced at 1/8th of an inch (2 mm) not only opens more cabbage cells but allows you to pack more cabbage into a jar dispersing more air. How to Slice Cabbage [Which is the BEST for Perfect Sauerkraut?]
- Add the proper amount of salt. Most literature puts this at 2.0-2.5% salt in relation to the weight of the sliced cabbage mixture, though I – and other artisanal fermentation companies – are getting consistent results with a 1.5% salinity. Below 1.5% will result in spoilage. My recipes are set up for a 2.0% salinity. See Salt by Weight for Delicious Sauerkraut… Batch after Batch for help adjusting these numbers.
- Keep your fermenting sauerkraut below the brine. This ensures that the pathogenic bacteria that love fresh air – and can ruin your sauerkraut – do not take up residence in your jar of goodness. In addition, the brine provides a moist environment for the bacteria. Bacteria are like sponges. They don’t pick up nutrients from dry cabbage but will absorb nutrients from the brine and the wet cabbage. Fermentation Weights: Keep Your Ferment Below the Brine
- Use a a lid with an airlock (or crock with a water-sealed lid). Yeast and molds need oxygen to survive. The less air you provide them the better. 9 TOP Fermentation Lids for Mason Jar Fermentation [HOW AIRLOCKS WORK]
- Ferment within the ideal temperature range of 65 and 72°F (18–22°C). This may mean waiting until cooler weather to ferment or creating a cooler environment. 11 Cool Fermentation Tips for Hot Weather
- Ferment in a 5-liter (or larger) water-sealed ceramic crock. The larger container and thicker walls create a more stable environment and results in consistently high-quality sauerkraut. Fermentation Crocks: The Who, What, Where, When, Why and How
- Ferment seasonally. Before refrigeration, this is how the harvest was preserved for enjoyment during the cold, winter months. This necessitates a way to store a year’s supply of sauerkraut – that is, a second refrigerator! 5 Ways to Store Fermented Sauerkraut [One is Controversial]
Five years into my sauerkraut making journey, not only did I have a second refrigerator – and a garage to house it, but I also had access to “winter” cabbage and for the past ten years have been making a year’s supply of sauerkraut each fall. Game changer!
WHAT TO DO WHILE THE MIGHTY MICROBES ARE WORKING FOR YOU
Once your jar of sauerkraut is safely packed and sitting in the right spot, your work is nearly done. Prepare yourself now for a long watch-and-wait period while our wonderful world of microscopic friends goes to work for you. You may be a bit nervous just leaving that jar alone on its own. Trust. It will not putrefy and turn to poison.
Here are a few tasks and tidbits to help you through the weeks ahead.
CATCH ANY OVERFLOWING BRINE
Your jar should be sitting in a small dish to catch the brine that typically overflows in the first few days. Check your dish daily during the first week. Empty and toss brine as need be.
Ideally, you do not want to lose this precious brine. It helps to keep your ferment anaerobic and provides moisture in your jar of finished sauerkraut. Brine overflow is caused by:
- Air bubbles trapped in your sauerkraut mixture.
- Jar packed too full. You’ll want to get into the habit of leaving 1-2 inches (3-5 cm) of space between the top of your packed sauerkraut and the top of your jar. This gives a place for brine to go as your packed sauerkraut expands.
- An unusually active batch. This is generally due to extra-high sugar levels in your ingredients and is more common if your sauerkraut includes shredded beets or other extra sweet ingredients.
If you are using an airlock, brine can flow up into the chambers. If this happens, wait until the bacteria at the early stages has finished creating the high levels of CO2 that cause the brine to move up – around Day 5 – then pop off the airlock, wash well and replace. If, however, small bits have somehow found their way into the airlock and it looks clogged, go ahead and take care of that right away.
MAKE SURE GASES ARE ESCAPING
If you are using a lid with some type of airlock, gases will escape as need be without any intervention by you.
If you are using the white plastic lid I recommend, or some other lid without an airlock, you may notice that the lid is bulging. This means you screwed it on too tight. To release the trapped gases, carefully loosen the lid just a tad, stopping the second you hear gases escaping or see liquid seeping.
IGNORE? OR NAB? THOSE FLOATY BITS
You should have placed a Floaties Trap – a cabbage leaf cut to size – on top of your packed sauerkraut, and below your weight. Most bits are held under the brine by this, but a few small bits might still manage to escape.
I generally leave them be though by being exposed to air, mold and yeast can grow on them. If you are overly concerned, go ahead and open your jar and fish them out.
WATCH FOR FERMENTATION SIGNS
These are the typical changes that your ferment will go through as if transforms from salty cabbage into flavorful sauerkraut.
Within a day or two, you should see little champagne-like bubbles slowly moving through the sauerkraut and rising to the surface. With some batches (usually those exceptionally high in natural sugars), you may even see a foam-like mass of bubbles collecting on the surface.
These bubbles are most predominate during the initial few days when the first bacterial strain to go to work (L. Mesenteroides) are eating the sugars in your cabbage and vegetables. This produces carbon dioxide, hence the bubbles. Their work also increases the acidity of the brine. When the acidity reaches 0.25 to 0.3% (calculated as lactic acid), the L. Mesenteroides die off – around Day 5 – and the bubbling slows down.
You may also hear an occasional fizzy sound as the bubbles work their way out of your jar.
The amount of bubbles you see depends somewhat on the sugar levels in your cabbage, which can vary quite a bit depending upon variety and growing conditions. Nutritional data shows that the sugar content in 5 types of raw cabbage ranged from 1.18 gram to 3.83 grams per 100 grams.
Though this is one of the key fermentation signs, don’t panic and toss your jar if you don’t see bubbles. They can be elusive and not every batch of sauerkraut progresses through each stage with perfect timing. You are not fermenting in a climate-controlled laboratory!
To reassure yourself that fermentation is progressing, try a few solid taps on the outside of the jar. You should see some bubbles begin to move up the sides of your jar. If not, and if your home is especially cool, you might need to move your jar to a warmer spot.
CLOUDY BRINE, WHITE SPECKS AND COLOR CHANGES
The brine in your sauerkraut may slowly change from clear to cloudy and you may notice some white sediment forming at the bottom of the jar. This white powder is from the bacteria and is perfectly normal. If your sauerkraut contains beets, turmeric or other deeply colored vegetables, you may see the brine change to match the color of what you are fermenting. You may also notice dirty specks of color – especially when using carrots or beets – forming at the top of your jar.
The cabbage and vegetables in your sauerkraut will lose their brightness and the cabbage will become somewhat translucent.
Old gym socks? Rotten eggs? Sulfur? Even bleach!
Yes, the smell is one of the fermentation signs to “look” for.
Those are just a few of the terms used to describe what fermenting sauerkraut smells like. The sulfur-containing compounds in cabbage – and other cruciferous vegetables – are what produce these strong and pungent odors. Just remind yourself the numerous nutritional benefits they are packed with as your nose adjusts to the odors. Sadly, many a spouse has banished fermentation from the home due to the smells of fermentation.
For some, however, they are not sure if the smell indicates all is well in their jar and they worry that their fermenting sauerkraut is turning to poison. It isn’t!.
But, if you are totally new to sauerkraut and not sure how it should smell, buy a jar of sauerkraut to get a sense of what sauerkraut smells like. Look for raw, unpasteurized sauerkraut in the refrigerated section of a natural foods store. Compare its smell to what you have fermenting and nibble on it while you wait for your sauerkraut to ferment.
If, however, your sauerkraut smells like rotting or putrid food, you’ll want to toss it. Try to figure out what went wrong and then try another batch.
If you are fermenting during hot weather, or if your brine levels dropped to expose your top layer of sauerkraut, you may notice that the top layer of your sauerkraut has turned brown. This is from oxidation and this section will have reduced levels of Vitamin C. The general recommendation is to toss this oxidized layer when you get ready to eat your sauerkraut. Those who hate to waste can just mix the oxidized layer in with the rest of the sauerkraut.
You may also notice the brine turning brown. This is usually due to fermenting in warm weather.
MONITOR BRINE LEVELS
Brine movement by temperatures. For most of the first week, you’ll notice plenty of brine and your packed sauerkraut should remain under this brine. However, you may observe that the level of the brine moves up and down throughout the day. In fact, I find it rather fun to monitor the temperatures in my home by the brine level in my jar of fermenting sauerkraut. Our house tends to be cooler at night and warmer during the day. When I first check on my jar in the morning, I might find the brine level is below the top surface of my ferment. Then, as the house warms up, the brine level rises to almost the top of the jar.
Brine drops below the top of sauerkraut. After the first 7-10 days, you may see the brine level drop and the upper part of your sauerkraut remain exposed and not covered in brine. This is normal, especially in the small environment of a jar, and happens when the active stage fermentation is complete. No worries. By this point, the lactic acid has reached a high enough concentration that molds and yeasts can’t grow on the exposed surface.
Add extra brine? I used to keep adding brine at this stage only to find it disappear again. I also found that not only did the additional brine add extra salt, but that it diluted the flavors I worked so hard to achieve. I no longer recommend adding brine to your ferment.
DEAL WITH HEAVING
Do you notice your packed mixture of sauerkraut expanding and moving up in your jar and causing brine levels to rise? This is “heaving” as described in Malolactic Activity of Lactic Acid Bacteria during Sauerkraut Fermentation:
“Heaving has been described as the increase in sauerkraut volume because of rapid CO production by heterofermentative LAB, resulting in gas entrapment within the sauerkraut and a rise in brine level in the tank.“
In other words, excessive CO2 is being produced. Rates are influenced by the concentration of malic acid in your particular head of cabbage. The Leuconostoc mesenteroides bacteria that are active during the first few days of fermentation, are converting malic acid to lactic acid and producing CO2. The more active the Leuconostoc mesenteroides, the greater the CO2 production.
By the way, bacteria are broken into two main categories: Homofermentative and heterofermentative. Heterofermntativebacteria produce more than one compound: lactic acid, acetic acids and alcohol in this case and homofermentative bacteria, just one compound. This gal that barely passed her high school biology class is still learning. 🙂
Trapped air bubbles forcing brine out? If air bubbles get trapped in your sauerkraut, the mixture will expand and force your fermentation weight up, making it look like there is no brine.
To release these trapped bubbles, first remove the lid, then either push down on the weight, slide a butter knife along the inside of the jar or poke the sauerkraut with a bamboo skewer. Doing so will release the air bubbles and allow the sauerkraut to condense back down into the jar and the brine to once again cover the top of it. This will ensure that your sauerkraut mixture remains below the brine and that fermentation unfolds in the absence of oxygen.
CONSIDER ADDING A FERMENTATION “GATE” TO YOUR FERMENTATION TOOLBOX
As I expand my fermentation repertoire and also better understand why my ferment might bulge above the brine, I am slowly seeing the benefits of a device that is strong enough to contend with the power of the Mighty Microbes furiously working away in a jar of fermenting sauerkraut. I have used fermentation weights – Pickle Pebbles – but find that every once in a while they are not heavy enough, especially with an extra active batch of sauerkraut.
Fermentation Gates is a term I have coined to describe a device safely locked inside the neck of your jar, that no matter how much force you apply to it – or how much gas is created by the Mighty Microbes – it will not open, or move up the jar. Your ferment does not bulge up and out of the brine.
The silicone Pickle Pusher by the Ultimate Pickle Jar,
the plastic Canning Buddies by ViscoDiss,
the stainless steel Fermentation Lid by KrautSource,
the stainless steel – made in the USA – PickleHelix by Trellis and Co. and
the glass jelly jar I use in my teaching recipe are all examples of Fermentation Gates.
See Can I Use Plastic? Silicone? Stainless Steel? for Fermentation for a discussion on how the various materials perform in the acidic environment of fermentation.
Nothing is foolproof, but I am generally finding that my ferments remain below the brine throughout fermentation when using one of these devices. I have reviewed the first three and have been using the PickleHelix, but have yet to put a review together for it. Please note that the link to the PickleHelix might be just for the lids. Their company just moved manufacturing to the US and I believe they may be struggling to meet current demand.