Fermentation - Sauerkraut

Introduction

The practice of fermenting cabbage to create sauerkraut has been recorded in history as far back as Roman times.  More specifically, sauerkraut is a product of lacto-fermentation (so-called because the microorganisms involved create lactic acid, not because of any association with dairy products).  These days, most commercial sauerkraut gets its tangy flavor from vinegar and is heat-treated for shelf-stability, whereas lacto-fermented sauerkraut is a live cultured food, teeming with beneficial bacteria that not only enhance flavor, but aid digestion as well.

The Basics: Cabbage is shredded and submerged in a salty brine for several days to several weeks, depending on how sour you want your sauerkraut.  

Quick Reference
 Batch Size Cabbage Salt

1 qt.

2-3 lbs. 1 tbsp.
1 gal. 8-10 lbs. 1/4 cup
5 gal. 40-50 lbs. 1 cup
Materials
  • fermentation vessel of desired size (glass, food-grade plastic, or non-leaded ceramic)
  • green or red cabbage (one medium-sized cabbage, approx. 2 lbs., yields about 1 qt. sauerkraut)
  • non-iodized salt
  • kitchen knife or grater/slaw board
  • large bowl
  • tamper (optional)
  • weight
  • (optional) reCap mason jar lid and airlock with rubber stopper
Instructions
  1. Wash all utensils thoroughly with warm water and vinegar.
  2. Shred cabbage using a grater or slaw board.  Or, for coarser-textured kraut, cut cabbage in fourths, remove core pieces, and slice across grain.
  3. In large bowl, combine cabbage, salt and desired seasonings and let stand for 20 minutes.
  4. Massage cabbage for about 5 minutes.  Brine is created as salt pulls water out of the cabbage.
  5. Pack cabbage mixture into jar or crock and tamp down so that brine rises about 1" above cabbage.  Leave 1-2" of headspace at top of jar to avoid overflow (carbon dioxide production will push cabbage and brine up).
  6. Place weight on top of cabbage to prevent it from floating to the surface and being exposed to air.
  7. Cover fermentation vessel.  Airtight is best for keeping dust, molds, and stray yeasts out, but as long as the cabbage stays well below the surface of the brine it shouldn't be affected by any air-borne contaminant.  Traditional crocks use a water-filled rim and notched lid combo to allow fermentation gas to escape while remaining airtight to the outside.  We use a reCap lid with an airlock and rubber stopper to achieve the same results.  
  8. Let stand in a cool, dark place (around 68°F or 20°C) for 2-4 weeks.  As fermentation proceeds, the flavor of your sauerkraut will get increasingly more tangy and complex.  After 2 weeks, taste your sauerkraut to see if it's to your liking.  Don't double dip and don't open it too often.  Every time you do, you're creating an opportunity for outside bacteria or molds to get in, which can lead to contamination.
  9. When you think it's done, move it to the refrigerator for long-term storage.  Fermentation will slow way down, but will not kill the beneficial microbes you've cultivated.  Enjoy!
Frequently Asked Questions

How does fermentation work to preserve food and keep it safe?

Simply put, beneficial bacteria break down the starches in fresh food and create lactic acid, which lowers the pH so that spoilage bacteria cannot survive.  In reality, the process involves successive waves of different strains of bacteria, each producing the conditions for its successor.  The first bacterial strains do not have to be added to the mix; they arrive in the folds of the cabbage leaves because they come from the environment outside.  But, adding the culture-rich brine from a completed batch can get a fresh batch off to a quicker start.

Can I make sauerkraut without using salt?

The purpose of salt in making sauerkraut is to keep the cabbage from getting too soft and to create an initial environment that favors the growth of certain strains of beneficial bacteria (including lactobacillus, the bacteria responsible for turning milk into yogurt) while preventing unwanted bacteria that lead to rot.  Preferable to a no-salt sauerkraut would be a low-salt sauerkraut, although its shelf life won't be as long as that of a fully-salted sauerkraut.  Low-salt sauerkraut can be made with as little as 1 tsp. salt for a 1-qt. batch.   For a truly salt-free sauerkraut, fermentation guru Sandor Katz describes three methods in his book Wild Fermentation: 1) pour 1 cup of wine over tightly packed cabbage so that it rises like a brine, 2) use 1 tablespoon each ground caraway, celery, and dill seeds mixed in with cabbage, or 3) soak 1 ounce  dried seaweed in hot water, chop and add it to grated cabbage, and use the water it was soaked in as a brine.

What if there's not enough brine to cover my cabbage?

The fresher your cabbage is, the more moisture it holds and the easier it will be to work a brine out of it.  If you don't have enough brine to cover the cabbage by at least 1 inch, you can make more by dissolving 1 tablespoon salt (15 milliliters) in 1 cup water (250 milliliters).  It is important for the brine to completely cover the cabbage because fermentation is an anaerobic process, meaning it takes place in the absence of oxygen.  Cabbage that floats to the surface can come in contact with contaminating organisms.

What can I use to keep the cabbage from floating if I don't have fermentation weights?

Fermentation weights are just ceramic disks (some are divided into half-circles or two interlocking pieces, which is convenient if you need to insert them into a container whose opening is smaller than its cavity is wide).  However, if you use a crock or other container with straight sides, you should be able to find a small plate or saucer that fits reasonably well inside.  You can place additional weight on the saucer by topping it with a rock (sterilized in boiling water) or a plastic bag or jar filled with water.  If you're using a wide-mouth quart jar, a small (125 or 250 ml) jelly jar will fit inside.  To keep the cabbage from floating up around the bottom of the inner jar, cut a disc of plastic out of the top of a large yogurt container to fit the inside bigger jar and place it over the cabbage.  A drawback of these kind of improvised set-ups is that you may have a jar or other weight sticking out of the top of your fermentation container, so you won't be able to put a lid on it.  In that case, cover it with cheesecloth to keep out dust and flies and use a rubber band to keep the cloth in place.

What if I see mold or white scum on the surface of my sauerkraut?

If you monitor your sauerkraut every day, you should be able to catch something like this at an early stage.  White "scum" is a residue of yeast formation.  It is completely normal (like the lees in unfiltered beer), though unappealing so you can simply skim it off whenever you see it.  The same goes for mold, if it's an isolated spot that's easily removed.  Molds form just on the surface where they have access to air, so if your cabbage is well below the surface of the brine, it may not be affected at all.  If any part of the cabbage does appear affected or discolored, you can try salvaging the sauerkraut by scooping out the affected portion and pushing the remainder back down below the brine and weighting it down.  If the contamination returns or if the sauerkraut smells "off," discard it.  Fermented foods should smell tangy and sour, but pleasingly so.  Rotten or putrid smells indicate that something has gone wrong and the sauerkraut should not be eaten. 

Additional Resources

Katz, Sandor Ellix.  Wild Fermentation: The Flavor, Nutrition, and Craft of Live Culture Foods.  2003.  (order here)   Our go-to reference for all things fermentable.  Beginner-level info that is easy to follow and plentiful recipes that are easy to execute with success.

http://www.wildfermentation.com/  Regularly updated with new and interesting ferments to try at home, as well as Sandor's workshop tour schedule.

http://www.culturesforhealth.com/cultured-vegetable-fruit-condiment-recipes.  A wide range of recipes for all sorts of cultured foods for when you're ready to go beyond sauerkraut.

Katz, Sandor Ellix. The Art of Fermentation: An In-Depth Exploration of Essential Concepts and Processes From Around the World.  2012.  (order here)   Lots more information than Katz's first book about the history and cultural practice of fermentation around the globe.  Recipes are more advanced and more unusual.


Sauerkraut Supplies

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