How to Ferment Vegetables: Salt, Time and Steps
Published
To ferment vegetables, salt them, keep them under the liquid and hold them at 68 to 72°F (20 to 22°C) for about 3 to 4 weeks. Illinois Extension gives a 3% brine for shredded vegetables and a 5% brine for whole or large pieces. For 2 lb (0.91 kg) of carrots, the calculator's default is a 5% brine with 47.3 g of salt in 1 quart (0.95 L) of water.
This guide uses carrots as the worked example and notes where cabbage and kimchi differ.
Quick answer
For carrots, use a 5% brine: 47.3 g (1.7 oz) of salt per quart of water. Ferment for 21 to 42 days, depending on the room temperature.
- Diamond Crystal kosher, per quart of water
- 3/8 cup
- Morton kosher, per quart of water
- 3 1/2 Tbsp
- Table salt, per quart of water
- 2 1/2 Tbsp
- For 2 lb (0.91 kg)
- 47.3 g (1.7 oz) of salt in 1 quart (0.95 L) of water
- Ferment window
- 21 to 42 days
- depends on room temperature, see the table in the guide
Warnings
Ferment at 68 to 72°F (20 to 22°C). University of Minnesota Extension says temperatures over 78°F (26°C) can cause over fermentation and spoilage and temperatures below 60°F (16°C) inhibit fermentation. Illinois Extension says spoilage bacteria may take over if it is too warm.
Discard the ferment if it is slimy or smells spoiled or rotten (Illinois Extension). NCHFP's Dill Pickles page (https://nchfp.uga.edu/how/ferment/recipes/dill-pickles/) says to discard fermented pickles that become soft, slimy or develop a disagreeable odor.
Keep the vegetables under the brine for the whole ferment. Vegetables that stick out of the liquid are exposed to air, which lets mold and yeast grow.
Do not reduce the salt below the amount shown. The National Center for Home Food Preservation says salt is vital to the safety and texture of fermented vegetables and not to cut back on the salt required, and the Inyo-Mono Master Food Preserver Program (UC Cooperative Extension) says it is unsafe to reduce salt in lactofermented vegetables.
Fermenting is not canning. This calculator gives no canning instructions. Do not can the fermented result unless you follow a tested canning procedure from the National Center for Home Food Preservation or a university extension service.
Notes
Published salt ranges: UC Davis says adding salt at a weight of 2% to 10% is important to prevent growth of harmful microorganisms; it does not say whether that is a percent of the vegetables or of the brine. The Inyo-Mono Master Food Preserver Program (UC Cooperative Extension) says tested recipes will fall between 2% and 10% brine concentrations. Illinois Extension gives 3% for shredded vegetables and 5% for whole and large pieces. Wild Fermentation's page Vegetable Fermentation Further Simplified (https://www.wildfermentation.com/vegetable-fermentation-further-simplified-2/) says ferments with less salt may be more prone to surface molds.
University of Minnesota Extension says a ferment is ready when the pH is 4.60 or lower and bubbling has stopped. UC Davis says the pH must be below 4.6 to prevent botulism and that its overview of the process is not a validated process.
Sources word surface growth differently. NCHFP's Dill Pickles page (https://nchfp.uga.edu/how/ferment/recipes/dill-pickles/) says to remove surface scum or mold promptly from fermenting pickles. Penn State Extension says not to taste kraut that shows mold. The Humboldt and Del Norte Master Food Preservers (UC Cooperative Extension) say white scum on kraut is from yeast, should be removed daily, and is no reason to discard the kraut.
Use salt without iodine or anti-caking additives. University of Minnesota Extension says iodine can interfere with fermentation, and Illinois Extension recommends additive-free salt. The same weight of salt fills a different volume for each salt type, so weigh the salt.
Do not ferment in copper, iron or galvanized metal containers or in lead-glazed crocks (Illinois Extension's fermentation handout, https://extension.illinois.edu/sites/default/files/fermentation_handout_2020.pdf, and Penn State Extension's sauerkraut publication, https://oc4h.ucanr.edu/sites/default/files/2020-10/337943.pdf). University of Minnesota Extension says to avoid metal containers because the metal reacts with the lactic acid.
Fermentation times for carrots follow general extension guidance for fermented vegetables, not a source written for carrots. University of Minnesota Extension and Illinois Extension give 3 to 4 weeks at 68 to 72°F (20 to 22°C). The 60 to 67°F (16 to 19°C) row of 35 to 42 days is an inference: University of Minnesota Extension says fermentation may take 5 to 6 weeks below 68°F (20°C) and that temperatures below 60°F (16°C) inhibit it, but no page states a 60 to 67°F range. Sauerkraut, red cabbage and cucumber pickles use different bands (70 to 75°F and 55 to 65°F or 60 to 65°F) because their times come from NCHFP pages written for those foods.
The Dietary Guidelines for Americans recommend that adults limit sodium to less than 2,300 mg per day. Brined and fermented food contains added salt.
The water shown is a default of 0.5 quarts per pound of food. Use enough water to cover the food completely. The salt follows the water: if you use a different amount of water, enter it and the salt changes with it.
What fermentation does
Naturally occurring bacteria such as Lactobacillus turn the sugars in vegetables into lactic acid and carbon dioxide, according to University of Minnesota Extension. The acid lowers the pH of the vegetables, which preserves them. Illinois Extension adds that the salt pulls water and sugars out of the vegetables and favors the fermenting bacteria over spoilage bacteria, yeasts and molds. The bubbles you see are the gas the bacteria produce.
This is a different process from the vinegar pickling and canning that this site does not cover. A fermented vegetable gets its acid from bacteria, not from added vinegar.
Choose brine or dry salt
A brine ferment dissolves the salt in water and covers the vegetables with it. Illinois Extension says brining is best for whole or quartered pieces, because it gives better coverage. A dry-salt ferment mixes the salt directly into shredded or grated vegetables, such as cabbage or carrots, and presses them until the salt draws out the juice. The juice then becomes the brine.
The two methods use different bases for the percentage, so read the "of water" or "of vegetables" label. The Brine Math sheet, from the Inyo-Mono Master Food Preserver Program, gives the 2% to 10% range in the note below. Brine percentages explained covers the two bases.
| Strength | Salt percentage | Salt per quart of water | Salt per gallon of water | Time at room temperature |
|---|---|---|---|---|
| Standard brine, 3% Brine of 3% salt by weight of water. Illinois Extension calls a 3% brine generally safe for shredded vegetables and says whole and large pieces should use a 5% brine, so 3% is the strength for shredded vegetables and the 5% strength is the default for whole or large pieces. Illinois Extension does not name carrots. | 3% of water | 28.4 g (1 oz) 3 1/2 Tbsp Diamond Crystal kosher 2 Tbsp Morton kosher 1 1/2 Tbsp Table salt | 114 g (4 oz) 7/8 cup Diamond Crystal kosher 1/2 cup Morton kosher 3/8 cup Table salt | 21 to 42 days |
| Firm brine, 5% Brine of 5% salt by weight of water, the strength Illinois Extension gives for whole and large pieces of vegetables. Illinois Extension does not name carrots. It is the default for whole or large pieces. | 5% of water | 47.3 g (1.7 oz) 3/8 cup Diamond Crystal kosher 3 1/2 Tbsp Morton kosher 2 1/2 Tbsp Table salt | 189 g (6.7 oz) 1 3/8 cups Diamond Crystal kosher 7/8 cup Morton kosher 5/8 cup Table salt | 21 to 42 days |
Weigh the salt when you can. The same volume of different salts weighs different amounts.
| Strength | Salt percentage | Salt per pound of food | Time at room temperature |
|---|---|---|---|
| Grated carrots, dry-salted, 2.5% Grated carrots massaged with salt at 2.5% of their weight; the juice that collects becomes the brine. | 2.5% of food | 11.3 g (0.4 oz) 1 1/2 Tbsp Diamond Crystal kosher 2 1/4 tsp Morton kosher 2 tsp Table salt | 21 to 42 days |
Weigh the salt when you can. The same volume of different salts weighs different amounts.
Warning
Press the salted vegetables down and weigh them so they stay under the juice they release for the whole ferment. Vegetables that stick out of the liquid are exposed to air, which lets mold and yeast grow.
Salt and time by weight
| Vegetables | Salt by weight | Diamond Crystal kosher | Morton kosher | Table salt | Water |
|---|---|---|---|---|---|
| 1 lb (0.45 kg) | 23.7 g (0.83 oz) | 3 Tbsp | 1 1/2 Tbsp | 1 1/2 Tbsp | 0.5 quarts (0.47 L) |
| 2 lb (0.91 kg) | 47.3 g (1.7 oz) | 3/8 cup | 3 1/2 Tbsp | 2 1/2 Tbsp | 1 quart (0.95 L) |
| 4 lb (1.81 kg) | 94.6 g (3.3 oz) | 3/4 cup | 3/8 cup | 3/8 cup | 2 quarts (1.89 L) |
| 5 lb (2.27 kg) | 118 g (4.2 oz) | 7/8 cup | 1/2 cup | 3/8 cup | 2.5 quarts (2.37 L) |
| 10 lb (4.54 kg) | 237 g (8.4 oz) | 1 3/4 cups | 1 cup | 7/8 cup | 5 quarts (4.73 L) |
Weigh the salt when you can. The same volume of different salts weighs different amounts.
| Room temperature | Time |
|---|---|
| 60°F (16°C) | 35 to 42 days |
| 68°F (20°C) | 21 to 28 days |
The strength table above also lists the 3% Standard brine and the 2.5% dry salt for grated carrots. Illinois Extension says whole and large pieces should use a 5% brine and does not name carrots, so the calculator defaults carrots to the Firm 5% strength for sticks and larger pieces; 3% is the strength for shredded vegetables. The fermented root vegetables guide covers carrots with the other root vegetables.
What the time is based on
The carrot times follow general extension guidance for fermented vegetables, not a source written for carrots. University of Minnesota Extension and Illinois Extension give 3 to 4 weeks at 68 to 72°F (20 to 22°C). Recipes for carrots finish in 3 days to 2 weeks, and the calculator uses the longer minimum. The 60 to 67°F (16 to 19°C) row of 35 to 42 days is an inference, as the note below says.
Cabbage is different. The sauerkraut times are the NCHFP times for shredded cabbage: about 3 to 4 weeks at 70 to 75°F (21 to 24°C) and 5 to 6 weeks at 60 to 65°F (16 to 18°C), covered in the sauerkraut salt ratio guide. The kimchi time of 2 to 5 days is one recipe's room-temperature time, not a safety time, and the kimchi salt ratio guide covers it.
Steps
- Prepare the container. Use a food-grade plastic, ceramic or glass container or a fermentation crock. University of Minnesota Extension says to avoid metal containers, because the metal reacts with the lactic acid that the bacteria produce.
- Weigh the vegetables. The salt is calculated from the weight, so weigh them before packing.
- Weigh the salt. Use salt without iodine or anti-caking additives, and weigh it because the same volume of different salts weighs differently. The kosher salt versus table salt guide explains how the salt types differ.
- Make the brine or salt the vegetables. For a brine, stir the salt into the water until it dissolves. For a dry-salt ferment, work the salt into the shredded vegetables and pack them down.
- Keep everything under the liquid. University of Minnesota Extension says to keep produce fully covered, with 1 to 2 inches of brine above it. Weigh the vegetables down if they float. Illinois Extension says to use a jar with an airlock lid.
- Ferment at 68 to 72°F (20 to 22°C). Check the container for bubbling, smell and anything on the surface.
- Taste and test. University of Minnesota Extension says the ferment is ready when the pH is 4.60 or lower and bubbling has stopped; if the pH is still higher, keep fermenting and test every 1 to 2 days.
- Move it to the refrigerator. University of Minnesota Extension says fermented produce keeps up to 9 months refrigerated.
Note
Sources differ on water. Illinois Extension's fermentation handout says filtered water or spring water is preferred and not to use distilled water. University of Minnesota Extension says to use soft or distilled water because hard-water minerals can discolor produce or change its texture.
Note
Do not ferment in copper, iron or galvanized metal containers or in lead-glazed crocks (Illinois Extension's fermentation handout and Penn State Extension's sauerkraut publication). University of Minnesota Extension says to avoid metal containers because the metal reacts with the lactic acid.
What to expect at each temperature
At 68 to 72°F (20 to 22°C), carrots take 21 to 28 days in the calculator. At 60 to 67°F (16 to 19°C) they take 35 to 42 days. University of Minnesota Extension says temperatures below 60°F (16°C) inhibit fermentation. Above 78°F (26°C) it says over fermentation and spoilage can happen. For cucumbers, NCHFP says temperatures above 80°F (27°C) make the pickles too soft, and for kraut it says above 75°F (24°C) the cabbage may become soft.
Note
Fermentation times for carrots follow general extension guidance for fermented vegetables, not a source written for carrots. University of Minnesota Extension and Illinois Extension give 3 to 4 weeks at 68 to 72°F (20 to 22°C). The 60 to 67°F (16 to 19°C) row of 35 to 42 days is an inference: University of Minnesota Extension says fermentation may take 5 to 6 weeks below 68°F (20°C) and that temperatures below 60°F (16°C) inhibit it, but no page states a 60 to 67°F range. Sauerkraut, red cabbage and cucumber pickles use different bands (70 to 75°F and 55 to 65°F or 60 to 65°F) because their times come from NCHFP pages written for those foods.
Warning
Ferment at 68 to 72°F (20 to 22°C). University of Minnesota Extension says temperatures over 78°F (26°C) can cause over fermentation and spoilage and temperatures below 60°F (16°C) inhibit fermentation. Illinois Extension says spoilage bacteria may take over if it is too warm.
Safety
Note
Published salt ranges: UC Davis says adding salt at a weight of 2% to 10% is important to prevent growth of harmful microorganisms; it does not say whether that is a percent of the vegetables or of the brine. The Inyo-Mono Master Food Preserver Program (UC Cooperative Extension) says tested recipes will fall between 2% and 10% brine concentrations. Illinois Extension gives 3% for shredded vegetables and 5% for whole and large pieces. Wild Fermentation's page Vegetable Fermentation Further Simplified (https://www.wildfermentation.com/vegetable-fermentation-further-simplified-2/) says ferments with less salt may be more prone to surface molds.
Warning
Keep the vegetables under the brine for the whole ferment. Vegetables that stick out of the liquid are exposed to air, which lets mold and yeast grow.
Warning
Do not reduce the salt below the amount shown. The National Center for Home Food Preservation says salt is vital to the safety and texture of fermented vegetables and not to cut back on the salt required, and the Inyo-Mono Master Food Preserver Program (UC Cooperative Extension) says it is unsafe to reduce salt in lactofermented vegetables.
Warning
Discard the ferment if it is slimy or smells spoiled or rotten (Illinois Extension). NCHFP's Dill Pickles page says to discard fermented pickles that become soft, slimy or develop a disagreeable odor.
Warning
Fermenting is not canning. This calculator gives no canning instructions. Do not can the fermented result unless you follow a tested canning procedure from the National Center for Home Food Preservation or a university extension service.
Note
University of Minnesota Extension says a ferment is ready when the pH is 4.60 or lower and bubbling has stopped. UC Davis says the pH must be below 4.6 to prevent botulism and that its overview of the process is not a validated process.
Note
The Dietary Guidelines for Americans recommend that adults limit sodium to less than 2,300 mg per day. Brined and fermented food contains added salt.
Problems and what causes them
A white film on top. UC Davis says this is usually yeast, often called kahm yeast, that grows at the surface. For sauerkraut it says to remove it periodically, because excess yeast can cause off flavors and reduce acidity. America's Test Kitchen calls the film on fermenting beets harmless and says to skim it off.
Mold. UC Davis says mold is typically green, blue, brown or black and grows where the ferment meets air, and that confirmed mold on any part of a ferment means it should be discarded. Sources word surface growth differently: NCHFP's Dill Pickles page says to remove surface scum or mold promptly from fermenting pickles, and the Humboldt and Del Norte Master Food Preservers (UC Cooperative Extension) say white scum on kraut is from yeast, should be removed daily, and is no reason to discard the kraut.
Soft vegetables. The sources tie softness to warmth: NCHFP's sauerkraut page says kraut fermented above 75°F (24°C) may become soft. Low salt can also give soft or slimy results in cabbage: the Humboldt and Del Norte Master Food Preservers (UC Cooperative Extension) say salt under 2% can give soft or slimy kraut.
A putrid smell. UC Davis says a putrid smell indicates a failed fermentation and the ferment should be discarded.
Where to go next
For cucumbers, how to make brine pickles covers salt-brine pickles. For other vegetables, the vegetable brine recipes guide sets out the 3% and 5% brines by vegetable, and the fermentation salt percentage chart lists the salt percentages. Enter your own weight in the calculator for the amounts.
Frequently asked questions
How much salt do I use to ferment vegetables?
Illinois Extension gives a 3% brine for shredded vegetables and a 5% brine for whole or large pieces. For dry-salted cabbage the calculator uses 2.25% to 2.5% of the cabbage's weight. Do not reduce the salt below the amount shown.
How long do vegetables take to ferment?
For carrots the calculator shows 21 to 28 days at 68 to 72°F (20 to 22°C) and 35 to 42 days at 60 to 67°F (16 to 19°C). Those times follow general extension guidance for fermented vegetables, not a source written for carrots alone.
What temperature should I ferment at?
68 to 72°F (20 to 22°C). University of Minnesota Extension says temperatures over 78°F (26°C) can cause over fermentation and spoilage, and temperatures below 60°F (16°C) inhibit fermentation.
How do I know the ferment is ready?
University of Minnesota Extension says a ferment is ready when the pH is 4.60 or lower and bubbling has stopped. Taste alone does not measure pH.
Is the white film on top mold?
Not always. UC Davis says a white film is usually yeast, often called kahm yeast. Sources word surface growth differently, and confirmed mold on any part of a ferment means it should be discarded.
Can I can the finished ferment?
Fermenting is not canning. This calculator gives no canning instructions. Do not can the fermented result unless you follow a tested canning procedure from the National Center for Home Food Preservation or a university extension service.
Sources
- How to make fermented pickles (University of Minnesota Extension)
- Fermenting (University of Illinois Extension)
- Brine Math (Inyo-Mono Master Food Preserver Program, UC Cooperative Extension)
- Troubleshooting fermented fruits and vegetables (UC Davis Food Safety)
- Sauerkraut (National Center for Home Food Preservation)
- Preparing Fermented Fruits and Vegetables at Home (UC Davis)