How-to Guide
Making Sauerkraut Safely: Salt, Brine, Scum, and Storage
The short answer
Sauerkraut works because salt pulls juice from shredded cabbage and creates a brine in which lactic-acid bacteria ferment out the sugars. The salt level is not a matter of taste; it is a safety and texture control. NCHFP's tested ratio is 3 tablespoons of canning or pickling salt for every 5 pounds of shredded cabbage (their full recipe is 25 pounds cabbage to 3/4 cup salt). Mix it in, pack firmly, and let the salt draw out the juices.
The cabbage must stay submerged under brine the entire time, because exposure to air invites mold and yeast. If the natural juice does not cover it, add a boiled-and-cooled brine of 1.5 tablespoons salt per quart of water. Ferment at 70 to 75 F for 3 to 4 weeks (cooler, 60 to 65 F, takes 5 to 6 weeks); below 60 F it may not ferment and above 75 F it may go soft. Check 2 to 3 times a week and remove any scum that forms.
Fermentation is done when bubbling stops. Fully fermented kraut keeps several months tightly covered in the refrigerator, or you can freeze or can it. Discard any batch that is soft, slimy, has an off or foul odor, or grows mold below the surface.
The salt ratio is a safety number
Use the tested ratio and weigh or measure carefully: 3 tablespoons of canning or pickling salt per 5 pounds of shredded cabbage. Too little salt produces soft kraut and lets spoilage organisms outcompete the good bacteria; too much slows fermentation and can make it bitter. Use canning or pickling salt, not table salt with additives, which can cloud the brine or darken the kraut.
Shred the cabbage finely, mix the salt through it thoroughly with clean hands, and pack it firmly into the container so the salt draws the juice out and the cabbage sits under its own brine. If after packing the juice does not rise to cover the cabbage, top it up with a cooled brine made of 1.5 tablespoons of salt per quart of water.
Keep it submerged, ferment cool, skim the scum
- 1Weight the cabbage under the brine — Cover the packed cabbage so it stays fully submerged (a brine-filled food-grade bag, or a plate with a jar weight). Air exposure is what lets mold and yeast grow.
- 2Ferment at 70 to 75 F — At 70 to 75 F fermentation takes 3 to 4 weeks; at 60 to 65 F it takes 5 to 6 weeks. Below 60 F it may not ferment; above 75 F the kraut may become soft.
- 3Check and skim 2 to 3 times a week — If you use jar weights, check the kraut 2 to 3 times each week and remove scum if it forms. A brine-filled weight bag can be left undisturbed.
- 4Know when it is done — Fermentation is complete when bubbling ceases. The kraut should smell and taste pleasantly sour, not foul.
⚠ Surface scum (a white film of yeast) should be removed as it appears, but mold anywhere in the kraut, sliminess, softness, or an off/foul odor means discard the whole batch, do not taste to check.
Storing finished kraut
Once bubbling has stopped, fully fermented sauerkraut can be stored several months tightly covered in the refrigerator. It can also be frozen, or canned for shelf storage using the NCHFP process (a hot pack is processed 15 to 25 minutes and a raw pack 20 to 40 minutes in a boiling water canner, depending on jar size and your elevation). Because those times change with altitude, follow the NCHFP sauerkraut page for the exact schedule rather than a generic number.
Whatever the storage method, keep the kraut covered by its brine, use clean utensils, and trust your senses: good kraut is crisp, tart, and clean-smelling. Anything soft, slimy, discolored, moldy, or foul goes in the trash.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- NCHFP - Sauerkraut (Fermenting) — 25 lbs cabbage and 3/4 cup canning or pickling salt; work in about 5-pound quantities adding 3 tablespoons of salt per 5 pounds; if juice does not cover the cabbage add boiled-and-cooled brine of 1-1/2 tablespoons salt per quart of water; ferment at 70 to 75 F for 3 to 4 weeks, or 60 to 65 F for 5 to 6 weeks; below 60 F may not ferment, above 75 F may become soft; with jar weights check the kraut 2 to 3 times each week and remove scum if it forms; fermentation is complete when bubbling ceases; store tightly covered in the refrigerator for several months, or freeze/can (hot pack 15-25 min, raw pack 20-40 min per elevation).