Fermentation: Preservation with Benefits

By: Diane Wright Hirsch, MPH, RD

Senior Extension Educator – Food Safety

making sauerkraut
Photo: Diane Wright Hirsch

Believe it or not, winter is coming. This is a good time to think about preserving some of the vegetables that you may find in your cold cellar or at the fall farmers’ market. Cabbage, of course, but really, that is just the beginning. Consider adding cauliflower, carrots, cucumbers, and daikon radishes…just about any vegetable can be fermented.

Fermentation as a food preservation method has a very long history, perhaps as long as 12,000 years. Cheese, yogurt, sauerkraut, kimchee, olives, salami, jerky, and bread; also, beverages such as hard cider, wine, beer, and coffee were all produced by the fermentation process. Some fermented foods have been critical to the food culture of a country or region. Think yogurt in the Middle East, sauerkraut (a source of vitamin C in the winter) in Germany and fermented sausages in Italy.

Years and years of food preservation via fermentation have resulted in the development of safe and effective methods for processing these foods. According to Dr. Fred Breidt, Jr., a USDA microbiologist who specializes in the safety of fermented and acidic foods, the scientific literature has never recorded a case of food poisoning from raw vegetables that have been fermented properly. Please note the key word, properly!

How does fermentation create a safe food product?

During fermentation, lactic acid bacteria consume the sugars or carbohydrates in the food, producing acid and flavor compounds. When fermenting foods at home, we rely on creating the environment needed for a safe and effective ferment. To allow for the growth of the desirable lactic acid bacteria, the process needs sufficient water (added or generated from the vegetable after salting), nutrients (the vegetable provides these), an appropriate amount of salt, and the absence of oxygen/air. The beginner should use tested recipes that are science based, provide the appropriate salt concentration and amounts of vegetable and, if needed, added water.

The beneficial bacteria and the lactic acid they produce in the fermentation process compete for and destroy the pathogens that can cause foodborne illness. This is not to say that you do not have to use safe food handling procedures when making sauerkraut or kimchi at home. Starting with ingredients that are contaminated with pathogens, or cross contaminated by dirty hands or work surfaces may result in a product that can’t be made safe by fermentation.

So, start with vegetables grown using safe practices—using properly composted manure or plant compost; safe water for irrigation; harvested with clean utensils and clean hands. Wash vegetables thoroughly before cutting them. Make sure all knives, cutting surfaces and hands are washed before preparing the vegetables.

Achieving a good ferment—using sauerkraut at the example.

Start with the freshest cabbage you can. That is not to say that cabbage that has been stored awhile is not useable. You may have to add water to older veggies if you cannot generate enough after salting and pounding or squeezing the cabbage.

Speaking of salt. The type of salt you use is important. Do not use any salt that is iodized. In fact you really want to use pure salt, without any anti-caking additives. Pickling salt is the best for fermentation properties. If pickling salt is not available, kosher salt may be a possible substitute. However, it is best if you measure the salt by weight rather than by volume—a tablespoon of kosher salt is actually lighter than pickling salt because it is flaked. You will need a larger volume of kosher salt, but the weight would be the same.

Do not mess with the amount of salt in the recipe that is usually given as a ratio based on the weight of the cabbage (i.e. three tablespoons of pickling salt for each 5 pounds of shredded cabbage). So, again, using a kitchen scale will yield a more accurate measurement and over time, you can standardize your process based on the weight of your ingredients.

The container used for fermenting your cabbage should be large enough to accommodate your cabbage. Generally allow a gallon for each 5 pounds of cabbage. Use a fermenting crock made of food-grade ceramics or stone, a glass container or food grade plastic. Clean with hot soapy water and rinse with very hot water before use. You will also need a weight to hold the cabbage under the brine while fermenting. You can purchase fermenting weights or simply weigh the cabbage down with a plate, held down with two or three glass jars filled with water or a large food-grade plastic bag (I use a turkey brining bag) filled with brine, in case it leaks into the product. The brine should be made of 3 quarts of water with 4.5 tablespoons of pickling salt.

Once your cabbage is shredded, salted, pounded (with your clean fist or maybe a potato masher) to release the liquid so that it covers the cabbage, cover with the weight to keep the cabbage under the brine. Place a clean towel over the whole thing to keep insects out.

Your fermentation container should be kept at a temperature of about 68-75 ºF. This is one reason I wait until later in the fall to make sauerkraut. My basement gets cooler then, making a good fermentation room. If it is too warm, fermentation may progress too quickly to spoilage. If too cool, the process will take longer.

Once the fermentation process begins, it will progress through three stages, as long as the temperature is desirable. First, Leuconostoc mesenteroides initiates sauerkraut fermentation. It produces carbon dioxide, effectively replacing the oxygen in the jar. This takes 2-3 days. Next, Lactobacillus plantarum and Lactobacillus cucumeris continue the ferment for about 10-30 days (temperature dependent). Finally, Lactobacillus brevis finish off the process, usually in less than a week. When you notice that there are no more bubbles at the side of your crock or jar, then the fermentation is complete.

Expect the whole process to take about 3-4 weeks. Check often to be sure there is no mold. Skim it off as soon as you see it. If allowed to remain, the mold can contaminate the whole batch and result in a waste of a lot of good cabbage.

After about 3 weeks, start to taste your sauerkraut. When it reaches the desired “tanginess”, remove from the crock and store in the refrigerator, covered in brine (you may have to add a bit of water), for as long as 4-6 months. Sauerkraut can also be canned in a water bath canner, but the process will destroy the microorganisms that are thought to benefit your intestinal health.

For information on growing cabbage in the home garden, contact the Home and Garden Education Center at ladybug@uconn.edu or 1-877-486-6271. For more information on fermentation and canning sauerkraut, go to the National Center for Home Food Preservation at www.uga.edu/nchfp.