Fully fermented sauerkraut can be canned in a boiling-water bath. Fresh cabbage cannot. Fermentation is what makes the water bath safe: lactic acid bacteria drop the pH below 4.6, the level at which Clostridium botulinum cannot grow. The National Center for Home Food Preservation (NCHFP), using the USDA Complete Guide to Home Canning, publishes tested boiling-water times for both hot pack and raw pack. Pressure canning is unnecessary and makes the kraut soft.
Why a water bath is enough once the kraut is sour
Water-bath canning is only approved for high-acid foods. Plain cabbage is low-acid, so it is not a water-bath food. Sauerkraut becomes one only after a full salt fermentation.
Salt draws juice from the cabbage and favors lactic-acid bacteria over spoilage organisms. Those bacteria produce lactic acid. Properly finished kraut typically lands well below pH 4.6 — often around 3.5 to 4.2 — which is why a boiling-water canner is the tested method, not a pressure canner. Extension specialists specifically advise against pressure-canning sauerkraut: it is not needed for safety, and the higher heat softens the cabbage and destroys more of the flavor produced during fermentation.
The acid has to come from the ferment itself. Adding vinegar to raw cabbage and calling it sauerkraut is a different product (a quick pickle) and needs its own tested recipe. Cutting the salt in the ferment to make a “low-sodium” version is also outside the tested method. In fermented kraut, salt is part of the safety system, not only a seasoning.
What has to be true before the jars go in the canner
Canning is the last step, not the first. The cabbage must already be fully fermented.
The USDA/NCHFP method uses firm, fresh cabbage and canning or pickling salt — not iodized table salt or salt with anti-caking additives, which can cloud the brine and interfere with fermentation. The published large-batch ratio is 25 pounds of cabbage to ¾ cup canning or pickling salt. Shred the cabbage, mix thoroughly with the salt, and pack it firmly so the salt pulls out enough juice to cover the cabbage. If the juice does not cover it, add a boiled-and-cooled brine of 1½ tablespoons of salt per quart of water. Keep the cabbage submerged. Skim scum if it forms.
Temperature controls both safety and texture:
- About 70–75°F: fully fermented in roughly 3 to 4 weeks.
- About 60–65°F: often 5 to 6 weeks.
- Below 60°F: fermentation may stall.
- Above 75°F: kraut is more likely to turn soft.
Finished kraut is uniformly tart, bubbling has stopped, and the color has shifted from bright green to a pale yellow-white. If it still tastes like salted raw cabbage, it is not ready. Mold on the surface that cannot be cleanly removed, a rotten or putrid smell, or slimy kraut means discard the batch. Do not try to “save” it by canning.
If you want live cultures, skip the canner. Fully fermented kraut kept tightly covered in the refrigerator holds for several months and still contains active lactic-acid bacteria. Boiling-water processing pasteurizes the jars. Shelf-stable kraut is sour and safe; it is not a probiotic food.
Hot pack or raw pack
Both packs are tested. The choice is mostly about texture and processing time.
Hot pack means bringing the kraut and its juice slowly to a boil, stirring often, then removing it from the heat and packing it firmly into hot jars with the juices. Headspace is ½ inch. Heat drives off air, so the processing time is shorter and the pack is usually tighter. This is the better choice if you want a more uniform fill and less floating cabbage.
Raw pack means filling jars firmly with unheated fermented kraut and covering it with juice, again at ½ inch headspace. It keeps a bit more of the fermented character, but the jars need a longer boil, and liquid levels can drop more in storage.
In either case, release air bubbles, recheck the ½-inch headspace, wipe the rims, and apply lids to manufacturer tightness. Use standard mason jars and new two-piece lids (or the lid type your jar maker rates for boiling-water canning).
Water-bath processing times
Place jars on a rack in the canner. Water must cover the lids by 1 to 2 inches. Bring the canner to a full rolling boil, then start the timer. Keep a steady boil for the whole time. If the boil stops, bring it back and restart the clock.
These times are from the NCHFP table for sauerkraut in a boiling-water canner.
| Style of pack | Jar size | 0–1,000 ft | 1,001–3,000 ft | 3,001–6,000 ft | Above 6,000 ft |
|---|---|---|---|---|---|
| Hot | Pints | 10 min | 15 min | 15 min | 20 min |
| Hot | Quarts | 15 min | 20 min | 20 min | 25 min |
| Raw | Pints | 20 min | 25 min | 30 min | 35 min |
| Raw | Quarts | 25 min | 30 min | 35 min | 40 min |
When time is up, turn off the heat and wait 5 minutes before lifting the jars. Cool them undisturbed for 12 to 24 hours. Remove rings, check seals, wash the jars, and store sealed jars in a cool, dark place. Refrigerate any jar that did not seal and use it within a few weeks.
Problems that show up after the jars cool
Liquid dropped below the cabbage. A fully fermented batch that was processed for the correct time and elevation is still considered safe if the seal is good. Do not open the jars and add brine or water. Extra water dilutes the acid and can push the product outside the tested recipe. Opening and reprocessing also softens the kraut a second time.
Kraut is mushy. Usual causes are fermenting too warm, cabbage that was not firm to start with, or packing it too loosely so it overcooks in the jar. Hot pack plus the shorter processing time generally holds texture better than a long raw-pack boil.
White sediment in the jar. Fine sediment is often spent lactic-acid bacteria from the ferment. It is a quality issue, not automatic spoilage. A bulging lid, spurting liquid, mold inside a sealed jar, or an off smell after opening means discard the jar without tasting.
Cloudy brine. Common with table salt, hard water, or a very active ferment. It is not by itself a sign the canning failed.
You want to can a small jar-ferment that is only a week old. A short ferment may not have finished acidifying, and a jar ferment is harder to judge than a crock. Water-bath times assume fully fermented kraut made by the tested salt method. If the kraut is not clearly sour and finished, refrigerate it and keep fermenting, or discard it. Do not shorten the ferment and rely on the canner to make up the difference.
What this method does not cover
Tested water-bath times apply to plain fermented sauerkraut. Kraut mixed with meat, oil, eggs, or large amounts of low-acid vegetables is a different product and is not covered by this process. Caraway and similar dry spices are commonly used in home kraut, but any substantial recipe change belongs in a tested variation, not an improvised one.
Canning also will not fix a failed ferment. The boil destroys microorganisms that are present at processing; it does not reverse spoilage that already changed the food, and it cannot restore acid that was never produced.
Shelf-stable jars are the right choice when you need pantry storage and do not care about live cultures. Refrigerator storage is the right choice when the point of the ferment is the live kraut. Both are valid. Only one of them uses the water bath.
Frequently asked questions
Can unfermented “sour kraut” cabbage be water-bath canned if I add vinegar? Not with the sauerkraut processing times. Vinegar pickles need a tested pickled-cabbage recipe with a known vinegar acidity and ratio. Salt-fermented kraut and vinegar pickles are not interchangeable.
Is a pressure canner safer for sauerkraut? No. Fully fermented sauerkraut is a high-acid food. Extension guidance is to use the boiling-water process. Pressure canning overcooks it and is not the recommended method.
Does canned sauerkraut still have probiotics? No. The processing heat pasteurizes the jars. For live cultures, keep fully fermented kraut in the refrigerator instead of canning it.
Why is my canned kraut less sour than the crock? Hot pack boils off some volatile aroma, and a very long raw-pack process can dull flavor. The acid is still there. An under-fermented batch will taste flat after canning because it was flat going in.
Can I reuse the fermentation brine to top up jars? Yes, if it is the original kraut juice and the kraut is fully fermented. Do not dilute that juice with plain water to stretch the fill. If you are short on juice at canning time, the tested makeup brine from the ferment stage is 1½ tablespoons of canning salt per quart of water — used to cover during fermentation, not as a way to water down finished kraut after the fact.