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I used to make sauerkraut in a large ceramic crock pot. Several cabbage heads fit into one pot and this is a good method to preserve large amounts of cabbage harvested in the fall.

Today long term preservation is not a major concern anymore. Cabbage has its lowest price around October but it is possible to buy it year round. Fermented cabbage keeps ageing and changes its taste over time. It becomes more sour as time goes on. Everybody loves sauerkraut in November/December but what is left of it in May is not so much appreciated anymore. It's over-fermented, quite soft and too sour.

I find it now much better to ferment small quantities in mason jars (quart jars, 1L jars). This way you have freshly made sauerkraut and you can also try different varieties (red cabbage, red beets, baladi cabbage aka flat cabbage, white cabbage, ...).

If you google "mason jar fermentation" then you will find all kinds of special tools and lids that you "need" for fermentation. THIS IS A SCAM. You don't need anything special.

The key point about successful and safe fermentation is: No oxygen. The lactic acid bacteria responsible for the fermentation of cabbage are anaerobic. You have to create conditions where those bacteria thrive and they will keep fungi, yeast or other bacteria out:

1. Salt: use a brine with 1% to 3% salt (by weight, e.g 2g salt in 100ml of water makes a 2% brine). Salt suppresses the growth of yeast but lactic acid bacteria are more tolerant to salt than yeasts. In other words: without salt we might end up with some sort of vegetable beer or wine but by adding salt we encourage the lactobacillus fermentation.
2. No oxygen: mold and fungi need oxygen. Lactobacillus is anaerobic. Oxygen can also be dissolved in water. This is why fish can live in water. To make the brine for fermentation you should use previously boiled water. The boiling is not primarily needed to sterilize the water but to reduce the amount of dissolved gases such as chlorine and oxygen. Note that the water needs to be at room temperature when you add it to the shredded cabbage. In other words: bring water to a rolling boil and then let it cool down to room temperature.
3. Fill the jar to the top to keep air out.
4. Have some sort of valve to allow gases (mostly CO2) and brine to escape from the jar without letting oxygen in.

Remove the ring during fermentation and put a weight on top to have the lid function as a valve (this jar contains red beets + red cabbage)

A water glass as a weight on top of the lid makes a perfect valve to allow brine and gasses to escape without letting air in

Vintage crown canning jar from 1950, made by Dominion Glass of Montreal

Dominion Glass Co. of Montreal in 1890, view from Papineau Street, not far from today's Jaques Cartier bride, source: https://collections.banq.qc.ca/ark:/52327/2082128

Dominion Glass, add from 1915

Remove the metal ring during the fermentation while brine is spilling out

A glass filled with some water makes a perfect weight. This results in the glass lid functioning as a valve

Tattler mason jar lids. These lids do not corrode in the presence of lactic acid and salt brine.

Mason jar fermentation recipe

Steps to ferment cabbage into sauerkraut:

1. Use a large mason jar. I do not use jars smaller than a pint (16oz, about 1/2 liter). The old Canadian Crown jars were made by Dominion Glass of Montreal and they are quart jars (1 quart = 32 fluid ounce = 946ml = just under 1 liter). A Canadian Bernardin 1L jar or an american 1 quart Ball jar will work as well. I find that 1 quart (about 1L) is the perfect size.
2. Prepare a salt brine: Bring water to a rolling boil, leave it in the pot and let it cool down to room temperature. This does not only sterilize the water it reduces also the amount of dissolved chlorine gas and oxygen gas from the water. Both elemental chlorine gas and oxygen gas are toxic to lactobacillus bacteria and we need to remove them to allow lactobacillus to thrive. Add 2 gram of salt per 100 gram (=100ml) of water. This makes a 2% brine. Any salt works.
3. Use a cabbage shredder or a knife to slice the cabbage.
4. Lightly salt the sliced cabbage.
5. Pack the jar with the cabbage.
6. Add some of the brine (prepared in step 2).
7. Pound and compact the cabbage and make sure that the spaces between the shredded cabbage are filled with brine.
8. Leave about 1 inch (2.54cm) of space at the top, fill this space with something: I use pebbles collected at the beach or a raw wood block (not treated or painted wood). This is to keep the cabbage as much as possible submerged in brine. If you use small stone pebbles then make sure they are inert to the acid that forms during fermentation. Quartz pebbles or granite pebbles work well. Any kind of sediment stone or porous stone should be avoided.
9. Fill the jar to the top with brine and cover the pebbles or the wood block until the jar overflows. Put the lid without the ring on the jar. Put a glass filled with water on top of the lid to weigh it down.
10. Set the whole jar (with the water glass weight on top) into a bowl. Some of the brine will overflow as gasses form. Don't try to account for the volume expansion by leave an air gap in the jar. Remember that you want to keep any oxygen out.
11. Temperature influences taste and fermentation speed. I find that the best results are obtained at 16'C to 18'C. I use the unheated garage or a cool corner in the basement.

Granite pebbles or a wood block can be used to keep the cabbage submerged

Mason jar with a wood block to keep the cabbage submerged in brine. The lid and the weight on top of the lid will push the wood block down.

Jar on the left: a mixture of red and white cabbage, mostly white cabbage, just started. Jar on the right: a mixture of red and white cabbage, mostly red cabbage, day 6. Red cabbage changes its color as the PH-value changes. It's first purple/blue and then pink/red as the environment become more acidic. You can see that the cabbage on the right is ready because it's pink

Fermentation myth and mistakes

• Myth: Iodzied salt contains iodine and can not be used: there is almost no elemental iodine in iodized salt. Salt is mostly NaCl. NaCl contains no elemental chlorine. The chlorine is bound. Table salt is iodized with KI (potassium iodide) or KIO3 (potassium iodate). None of them have free elemental iodine. Both elemental chlorine and elemental iodine are disinfectant agents and they would be detrimental to the fermentation process but they are not present here. KI (potassium iodide) can potentially oxidize and form elemental iodine (I2) but all commercial salts that contain KI have some dextrose in it to stabalize the KI. The problem with table salt is not the iodine but anticaking agents such as calcium silicate. Calcium silicate is also an antimicrobial. You are better off avoiding salts with any kind of anticaking agent. However I have used iodized table salts with anticaking agents and the cabbage still fermented. It just seemed like it had a slow start.
• Myth: You need a special fermentation lid to avoid mold: wrong. Mold forms when there is oxygen in the jar. You need some kind of valve function to allow brine and gasses to escape. A lid with a weight on top can do that. No special equipment is needed. Mold can not grow if the brine is oxygen free and the jar is initially filled to the top with brine.
• Myth: You need to add brine back as it overflows: don't open the lid until the day you eat the sauerkraut. The gasses that bubble up to the top contain no oxygen. No mold will form unless you let oxygen in. Some of the cabbage at the top might at the end of the fermentation process be above the brine level. It's not a problem as long as the gas is not oxygen.
• Myth: To avoid overflowing brine I leave an air gap at the top of the jar to account for the expansion. Don't do this. Air contains oxygen and potentially allows mold to grow.
• Myth: A bit of mold on top is OK. You can eat the rest. Wrong, mold will likely spoil everything and it will taste terrible.
• Myth: Botulinum toxin may form during the fermentation: Fermentation as described here has zero risk of resulting in botulinum toxins. The lactic acid formed during the fermentation will prevent botulinum spores from germinating.
• Not a great idea: Some people are fermenting cabbage by putting some kind of weight directly onto the cabbage and leaving the jar otherwise open. They have AN AIR-GAP between the weight and the jar which is filled WITH A BIT OF BRINE but there is more air on top of this gap. This is how I used to ferment in the big crock pot. It works as long as there is sufficient CO2 bubbling up while the winds and air circulation are reduced (e.g with a kitchen towel over the top of the crock pot). It works best with a large volume of cabbage because this gives you a large amount of CO2. This method is however risky. Mold might form and spoil everything. The method presented here with brine up to the top of the jar and a lid/valve to keep the air out is much safer. I would never go back to the "open fermentation" method.
• Myth: Kahm Yeast is normal: No. If you follow the procedure described here then you will not get any Kahm Yeast. Kahm Yeast is not as bad as mold (you can eat Kahm Yeast) but it does change the taste of the fermented vegetables below the yeast layer. Kahm Yeast is a slimy white yeast growing at the top of the ferment. If you have Kahm Yeast growing then your process is not perfect. Kahm Yeast can be avoided by filling the jar with brine all the way to to the top before putting the lid on. The brine will then overflow during the fermentation but you will not get Kahm Yeast unless there is something wrong with your lid.
• When to seal the jar: The fermentation activity of cabbage in brine reaches it's maximum after about 3 to 4 days and after about 5 to 7 days very little activity remains. Not much CO2 will be produced after 7 days and it's a good idea to take off the weight and screw on the mason jar ring (aka band). Screw it on well to make sure the jar is now totally gas tight. With changes in ambient temperature and general atmospheric air pressure changes the gas trapped inside the jar may contract a bit and there is not enough new CO2 produced to compensate for the loss in volume. This may result in a slight vacuum. The jar needs to seal now very tight to avoid that oxygen from the room air gets back into the jar. Kahm Yeast could form if tiny amounts of oxygen get back in. This is one of the reasons why "professional fermentation lids" with a basic valve function are a bad idea. They will never seal 100% and Kahm Yeast is very common when those lids are used.

Packing and compacting

It's a good idea to pound sliced cabbage a bit as this gets the juices out and allows the lactic acid bacteria to thrive. You can cut yourself a small wooden pounder stick as shown below or you can buy one.

Put a little bit of brine into the jar prior to adding the cabbage. This ensures that all the air can rise and get out prior to packing and compacting. If you don't do this then you might end up with some trapped air at the bottom of the jar. If you still have air bubbles after topping the jar up with brine then you can try to release them by pushing a chop stick down into the jar.

Wooden cabbage pounder (aka fermenting tamper). It's not straight because the human hand is actually not straight. This kind of shape makes it very comfortable to hold the stick.

Monitoring the fermentation progress

How fast the fermentation progresses depends not only on the temperature but also on the type of vegetable that you ferment. Shredded cabbage has a big surface area and it's the easiest fermentation that you can do. It will progress very quickly:

• The brine will overflow around day 3 as a large amount of CO2 forms between the shredded cabbage pices pushing some brine out.
• The brine becomes acidic as fermentation progresses. Even if you do not want to ferment red cabbage you can add a few slices of finely cut red cabbage somewhere at the bottom or the top of the jar. Red cabbage is initially blue or purple and it starts to turn into a bright red/pink color around day 5.

Fermentation ideas

• Add some garlic or onions
• Add coriander seeds or pepper or chili powder
• Add fresh dill
• Add fresh or canned wine leaves
• Add fresh yarrow
• Add some sliced carrots
• Fermented beets: I don't like cooked red beets but thinly sliced raw beets fermented together with some red cabbage is excellent. Red beets can have a ticker sirup like juice and that can cause problems for the CO2 to raise up in the jar. Often the beets will also be pushed up as gas bubbles form below them. This can cause problems.
• Fermented carrots: slice carrots into halfs or quarters (thin long sticks) and ferment them together with a bit of dill and a small amount of garlic.
• Fermented fries: slice potatoes and ferment them.
• Fermented Turnips: Ferment Turnip slices with either a small amount of red beets or a small amount of red cabbage. Add two bay leaves.

Red cabbage

Baladi cabbage aka flat cabbage, this is in my opinion the best cabbage for fermentation as it is cruncy and juicy

White cabbage

Wooden disk

• Beechwood
• Birch
• Ash
• Mountain Ash
• Apple Wood
• Suggar Maple
• Silver Maple
• White Pine

Wooden fermentation disk (aka fermentation pebbles), made from raw wood, untreated, no glue, you just stack them, the weight on top of the lid pushes them down

Storing salt

Store bought salt is often in a cardboard container or in a plastic bag. The cardboard box is an insufficient barrier for humidity and the plastic bags are the cause of the microplastics found in ancient salts. Salt grains are abrasive and hard. It just takes a rattling truck to generate some microplastics during transport. Good pickling salts are Windsor pickling salt, Redmond real salt, himalayan pink salt, sea salt and kosher salts but most other salts work too.

Make sure the salt looks dry when you buy it (no big lumps in the bag or box) and transfer it at home to a glass jar with a good seal. This will keep it free flowing because humidity can not get in.

Properly dried salt stored in a glass container with a proper seal will not form lumps even without anticaking agents

Vintage Canadian adds from Dominion Glass of Montreal

• Montreal Gazette, Aug 9, 1917
• Montreal Star, Aug 1, 1924
• Montreal Star, Sep 2, 1924
• Montreal Star, Oct 1, 1924