Fermentation is enjoying somewhat of a celebrity status these days. In 2010, a story in The New Yorker about fermenting guru, Sandor Katz, revealed what might seem like a cult of fermentation enthusiast. It painted a peculiar picture of dumpster divers fermenting scraps of food for meals. I imagine this scene was somewhat unfamiliar to the readers of The New Yorker at the time. Nonetheless, the piece ushered fermentation into the spotlight that has only grown brighter since. By 2013, Michael Pollan lavished praise on germs in The New York Times Magazine highlighting the beneficial bacteria found in fermented foods like kimchi.
Far from the subversive culture portrayed in the New Yorker article, it is now not uncommon to see stories of people with jars and crocks full of fermented foods bubbling away on kitchen countertops. Other stories espouse the health benefits of the microbes found in fermented foods. Chefs sing the praise of flavor profiles produced through fermentation. Fermented products are filling the refrigerated sections of grocery stores proudly advertising the “live cultures” in their product. Fermentation festivals are held in cities across the country from San Diego to Austin to Boston and New York. If you are willing to shell out a few bucks, you can learn basic fermentation techniques at one of the many fermentation workshops popping up around the country.
But why wait for a workshop when you can easily get started on your own? With a little understanding of how fermentation works and a few supplies you probably already have on hand, you can be just weeks away from a delicious, homemade sauerkraut or pickled vegetable.
When most people hear the word fermentation, they think about beer and wine. Although this is a guide to making non-alcoholic ferments such as DIY pickles and sauerkraut, let us start with the alcoholic beverages. While alcoholic content is perhaps what makes beer and wine our most endearing fermented products, but it also makes them a good starting point for talking about the science of fermentation. The alcohols in beer and wine are created through the fermentation of grains and grapes using a magical little fungus called yeast. Yeasts are tiny, single-celled microorganisms. They are special because they eat carbohydrates and respire alcohol and carbon dioxide. That’s right, alcohol is nothing more than yeast flatulence and tasty flatulence at that. Distilled liquors are simply concentrated yeast farts.
It is possible to get alcohol from soaked wheat berries or a simple grape juice, but part of making a palatable homebrew beer or wine is the process of creating an ideal environment for that yeast to thrive. Grains are malted to create enzymes and then ground and cooked into a wort to make the sugars readily available. Grapes are pressed into a must containing the yeast-rich skins. Then, commercial yeasts are introduced to the sugary mixture. Without going headlong into a discussion of yeast species, suffice it to say these commercial yeasts (usually Saccharomyces cerevisiae and Saccharomyces pastorianus), have what might be called a sugar party in this new environment. The yeasts eat the carbohydrates, now available as sucrose, maltose, glucose, and fructose, reproduce and keep farting alcohol and carbon dioxide.
As these little yeasts do their “work”, fundamental changes are happening in the sugary liquid. The sugar content and the associated sweetness decrease. The yeasts respire alcohol, carbon dioxide, and other acids which increases the acidity of the liquid and imparts sourness. Volatiles are released as a byproduct introducing aromas and flavors that make the final product. To control the final flavor of beers and wines, brewers and vintners are rather particular about cleanliness and sanitation. They are careful to create an environment where only desirable yeast strains survive, so they strive for a yeast-free and bacteria-free environment prior to adding the yeasts they do want.
What does this have to do with non-alcoholic fermentations? Well, this process of microorganism eating carbohydrates and imparting new flavors is fundamental to all fermentation. It is just a little more fun to tackle the boozy aspect first.
Unlike alcoholic ferments, vegetable ferments do not use yeast or any fungus for fermentation. They use bacteria. Specifically, most vegetable ferments use naturally occurring “good bacteria” from the genera Lactobacillus and Leuconostoc. Bacteria from genera Pediococcus and Streptococcus also play a role in vegetable and dairy ferments. Rather than producing alcohol, carbon dioxide, and other acids as byproducts of carbohydrate consumption, these bacteria produce lactic acid, carbon dioxide, and other acids. When you take a bite of sauerkraut, it is the lactic acid and other acids imparting the distinctive sourness which makes sauerkraut taste so different than its pre-fermented cabbage counterpart.
Simply leaving chopped up cabbage on your countertop will not result in sauerkraut. Like alcohol ferments, vegetable fermentation is about creating an ideal environment for those little bacteria to thrive. Fortunately, unlike brewers and vintners, it is not necessary to create a yeast- and bacteria-free environment before getting started. In fact, instead of introducing commercial bacteria, a home fermenter can harness the freely available bacteria on vegetables and all around us to get started.
We are surrounded by bacteria. It is on surfaces. Yes, even those just-wiped surfaces. It is on vegetables. Yes, even on vegetables in those sterile-looking plastic packages. It is on our skin. Yes, even on that freshly showered skin. It is everywhere. Most of the bacteria around us is not harmful. In fact, just like it takes an ideal environment for the so-called “beneficial bacteria” to ferment foods, it also takes an ideal environment for so-called “harmful bacteria” to cause infection. So, the key to successful fermentation is creating an environment where good, lactic-acid-producing bacteria can have a carbohydrate party where the bad (infection and decomposition producing) bacteria are not invited.
Fortunately, the bacteria responsible for fermenting vegetables are very tolerant to a salty, oxygen-free, acidic environment. This means, creating an ideal environment for vegetable fermentation is as simple as adding salt to water for a simple saline solution. Fermentation in initiated by Leuconostoc mesenteroides, a bacteria that thrives in a salty bath. It feeds on the carbohydrates in vegetables to produce lactic acid and carbon dioxide. The lactic acid increases the acidity of the bath which enables other species of Lactobacillus to start growing and feeding on carbohydrates as well. As the fermentation process proceeds forward, oxygen in the water is replaced by carbon dioxide. The leuconostoc and lactobacillus bacteria thrive in this high-acid, oxygen-free environment while oxygen-loving bacteria responsible for decomposition cannot survive. The lack of oxygen also prevents the vegetables from oxidizing and changing color or texture significantly.
Over time, the environment in the vegetable ferment is changing and so is the bacteria concentration. As mentioned, L. mesenteroides is the bacteria that usually starts a vegetable ferment and until sufficient acidity for other bacteria to thrive is reached, only L. mesenteroides is metabolizing and reproducing. As acidity increases, various combinations of Lactobacillus acidophilus, L. bulgaricus, L. plantarum, L. caret, L. pentoaceticus, L. brevis, and L. thermophiles become active, start metabolizing and reproducing. Each of these bacteria thrive over different ranges of acidity, salinity, and temperature. As each takes its turn metabolizing, it is also changing the environment so other bacteria species can become active. At any given time, a vegetable ferment may contain one or all of these bacteria.
For the fledgling fermenter, it is not important to know exactly what bacteria are active at any given time. What is important to know is that as the bacteria, acidity, and salinity change over time, so does the flavor. A young ferment where perhaps only L. mesenteroides and L. acidophilus are present may have a slightly sour flavor while retaining much of the fresh character of the vegetables. However, an older ferment that contains all of the bacteria species mentioned may have what is often described as a funky, sour flavor. A “funky, sour flavor” is not necessarily a disparaging description. In fact, many fermenting enthusiasts believe the funkier the better. However, if you are just starting out with fermentation, keep in mind that the longer a vegetable ferments, the funkier it will be. How funky it gets is entirely the preference of the fermenter, but the best way to dial it in is to taste the fermentations-in-progress.
All of this theoretical; biology information is fine, but the real test is applying this knowledge to start your own vegetable ferment and, more importantly, to not end up with a pile of salty, soggy, rotting vegetables. At its most basic, it really is as simple as pouring a saline solution over vegetables in a jar and waiting for the leuconostoc and lactobacillus to do their magic. There are recipe ideas and resources included in this guide. However, there are a few important things to keep in mind when starting your own ferments.
First, the vegetables must remain fully submerged in the saline solution. Exposed vegetables are probably the most common reason I have seen ferments fail. In fact, I looked in on a sauerkraut in my opaque crocks after five weeks. One little stray piece of cabbage cause a bloom of fuzzy, green, tentacled mold to start growing. Mold is prolific and I prefer to err on the side of caution with molds. The whole batch had to be pitched. In order to prevent the “bad” decomposing bacteria or mold or fungus from thriving, the vegetables cannot have any access to oxygen. There can be no stray pieces floating on the surface. There cannot be even a little bit peeking out through surface. Not only is it important to submerge the vegetable when you start, but they must also remain submerged. The water cannot be allowed to evaporate enough to expose the vegetables. If the water level drops, add more saline at the same concentration of the recipe. Evaporation can also be reduced with an airlock mechanism.
The best way to keep the vegetables submerged is to weigh them down. There are many creative ways to weigh down ferments including using large river rocks, filling a smaller jar with saline, filling a plastic baggie with saline, buying “fermenting weights“, bags of marbles, glass paperweights. When I got started, I found a smaller jelly-jar with marbles and saline fit perfectly inside a wide mouth jar. There are additional suggestions in the recipe that follows. Keep in mind, the brine is corrosive, so no metals for weights. If you cannot fit the vegetables and a weight while keeping all the vegetables fully submerged, get another jar.
Second, do not skimp on the salt. Both the good and bad bacteria can tolerate salinity up to 5% by weight or more. It is the lactic acid that staves off the bad bacteria. Various recipes call for various salt concentrations. When I first started, I used 5-7% salinity to be on the safe side. Now, I regularly ferment using between 2-5% salinity. These percentages are calculated by weight. One pint of water is 16 ounces and weighs 1 pound (454 grams), so 3.2 ounces (or 90 grams) of salt is 2% salinity by weight. Do not use a volumetric measurement, use a scale. If you weigh a tablespoon of fine sea salt it weighs different than a tablespoon of coarse kosher salt. Until you are familiar with fermenting, it is best to err on the side of a little extra salt. It is easier to dilute the salt later than save a rotting ferment. If your final ferment is too salty, rinse it or dilute the brine and let it sit for 24 hours.
Also, do not skimp on the quality of salt. In this case, it is not only the quantity but the quality of salt that is important. Most table salts use an anti-caking agent that can cloud a ferment. You can ferment using cheap table salt, but alternatives do not use anti-caking agents or have more flavor. Coarse kosher salt has no caking agents but is very neutral in flavor. Malden sea salt and grey sea salt have additional minerals adding to their flavor. There are many more options for sea salts; find one you like.
Thirdly, use fresh, good-quality vegetables. Fermentation is not a means of preserving vegetables that are already going bad. If the vegetable is getting soft, showing signs of decomposition, or is bruised, it will not make a good ferment. Bruised vegetables get mushier. Vegetables already showing decomposition might be far enough along to continue decomposing in the brine. Use good, fresh, minimally blemished vegetables. However, the vegetables don’t have to be perfect. By all means, use the ugly, odd-shaped vegetables.
Fourth, smell and taste your creations frequently. As I mentioned, a ferment I failed to check on for five weeks grew mold. Had I checked on it weekly, I might have seen the floater earlier. Another thing you are checking for is spoilage. Ferments do not necessarily smell pleasant to most people. They will smell sour, tangy, acidic, and even like flatulence; however, they should never smell rotten or repulsive. Although the final texture varies according to vegetable and conditions, generally, vegetables should remain intact and even firm. There are caveats—sliced cucumbers can get mushy while my krauts are always crunchy—but they should never be slimy.
Aside from looking for mold, rot, or spoilage, there are many reasons to check your ferments frequently. Fermentation is a living process dependent on living organisms, so it is changing over time according to conditions. By checking your ferments frequently, you can taste your way into your preferred flavor. Some people like a young, slightly sour ferment. Others like a more mature, funkier ferment. It is really up to your preferences, so taste it once in a while and see how you like it.
On checking your ferment, you might find a layer of white, cloudy, skummy stuff on the surface. This can be scary and off-putting during your first ferment. Unfortunately, out of caution, many people have tossed a ferment for fear that this growth is mold. While it might seem scary, that layer of white stuff is a bloom of kahm yeast. Kahm yeast is a byproduct of lacto-fermentation that appears at air-brine interfaces. It is harmless, but some people find it adds an off-flavor to their fermented vegetables. The best way to eliminate the layer of kahm yeast is to use an airlock mechanism to prevent the surface from being exposed to air. The carbon dioxide produced by the lactobacillus will push out any remaining oxygen. Keep in mind, even with an airlock, you expose the surface to air every time you open it to smell or taste, so it is still possible to develop kahm yeast with an airlock.
There might also be a layer of sediment inside the ferment. This is caused by flocculating bacteria. This is also not a cause for concern. As mentioned previously, various lactobacillus are active under different conditions. As one species goes inactive, they cluster together and fall to the bottom of the fermentation creating this sediment layer. While this can cause your ferment to cloud up when you move it around, it is perfectly safe.
Lastly, do not let an excess of carbon dioxide blow up your creation. On social media, there are often posts sharing the aftermath of a fermentation explosion. As the lactobacillus produce carbon dioxide, that gas can build up in a sealed jar. As more and more carbon dioxide is produced, the pressure inside the jar can increase to the point the jar explodes. Not only do you lose a ferment, but it is also dangerous. There are several ways to combat this pressure build-up. The easiest is to not use a lid or not tighten the lid. This lets gases escape. Others opt to “burp” their jars once or twice daily. This is a great practice, but it only takes one missed burp or a particularly active ferment to build up pressure. Here, I also like to use an airlock.
Since an airlock prevents evaporation, reduces kahm yeast, and prevents pressure build-up, I almost always use an airlock now. Airlocks, commonly used in brewing, can be found online or locally at homebrew store along with modified lids. They cost a few dollars and can be reused indefinitely. You can also modify plastic lids yourself to save money.
Remember, you are never alone. There are many resources online, in books, and new fermentation communities are cropping up every day. There are a few suggested books and resources following the recipe.
Now, it is time to start your first sauerkraut!
In the following recipe, I assume one large cabbage fills a 64-ounce canning jar. The amount of salt suggested is based on that 64 ounces.
- 1 Large Cabbage (~4lbs)
- 60g to 90g Salt (sea salt or kosher salt, non-iodized), this is 2-4% salinity
- Optional: Carrots, turnips, rutabaga, fennel, radishes, winter squash or other vegetables. Not recommended: potatoes, eggplant, sweet potatoes, yams, cucumbers (save these for pickles), summer squash, zucchini.
- 1 64-ounch Canning Jar
- Big, non-reactive bowls
- Sharp knives
- Optional: a tamper (I like using a cocktail muddler)
1. Chopping: Chop the vegetables to the desired coarseness for your sauerkraut. Separate the leaves. I typically prefer a finer sauerkraut, so I chop my cabbage very thinly. The finer the vegetables are chopped the easier it will be to extract water from the vegetables during the bruising step.
2. Salting: Sprinkle salt over the cabbage. I use about 2 tablespoons per head of cabbage, but you can use up to 4 tablespoons.
3. Bruising: This is the fun part! Using your hands, start squeezing and pounding the vegetables to bruise them and release the water. It will be tough at first, but as the water starts being released, it will get easier. This will take some time. The end result will be a puddle of liquid at the bottom of the bowl.
Taste your sauerkraut as you are bruising it. It will be like a salty coleslaw. The saltiness will mellow out over time. If the solution is not salty enough, decay and mold will result. If the solution is too salty, the lactobacillus will not survive. However, they do survive over a wide-range of salinity. If the sauerkraut ends up too salty after fermentation, it can be rinsed before eating.
4. Packing: Pack the cabbage into jars. It is important to pack the cabbage tightly and push out all the air. Air pockets will allow other bacteria to survive. As you are packing, the liquid will continue to be expelled. The goal is to have enough liquid above the solid vegetables to keep the vegetables fully submerged.
5. Weighting: For best results, leave a half an inch or more of liquid above the vegetables and an inch or more of headspace above the liquid. It can be more of less according to your preference and weighting method. Weigh down the vegetables to keep them submerged during fermentation.
Fermenters get creative about weighing down their vegetables. There is no one right way to do this, but here are some ideas:
- A baggie of washed pebbles or aquarium pebbles
- A baggie of 2% saline (use saline incase the baggie breaks)
- A smaller jar filled with saline
- Glass weights
- Ceramic weights
Remember, you don’t need anything fancy or expensive; you just need to keep the solids under saline!
6. Waiting and Burping: Now, it is time to wait for the lactobacillus to do its work. Store your jar in a cool place out of direct sunlight. I have stored mine on the counter throughout the summer, so the temperature range is pretty wide. However, the warmer it is, the faster the souring. Also, sauerkrauts taste differently in different seasons; this is partly because of temperature and partly because of wild yeasts available. How your sauerkraut waits depends on preference, but here’s some options:
Burping: Tighten the lid on your jar completely and “burp” the jar once or twice a day. As the or you might have an explosive mess on your hands. Burping regularly also allows you to check fluid levels regularly.
Unsealed Jars: To avoid the explosiveness predicament and to eliminate the need to remember to burp every day, you can simply use a loose lid or even just a piece of fabric held on with a rubber band. The gases release on their own, but sometimes you forget that sauerkraut is on the counter until weeks later. The liquid also evaporates more quickly with this method. For me, I also tend to get a kahm yeast layer on top of the liquid more easily with this method.
Airlocks: You can buy or make airlock adaptors for canning lids that eliminate the need for daily burping, minimize evaporation and even reduce the kahm yeast growth. Here is one version on Etsy, but there are others. If you are handy with a drill, these can easily be made.
Note: You can start tasting your ferment within the first week. It is fun to test out the ever-evolving flavors in a ferment. As the acidity changes, the flavors change due not only to the acidity, but also to the changing nature of the bacteria. Different lactobacillus survive at different acid levels. Personally, I have let ferments go as long as 8 weeks (that forgotten jar with an airlock on the counter). I like a 6-week fall ferment, but it is your preference. After 8 weeks, the flavors get a little too funky for my palette.
7. Refrigerate: Once the sourness and flavor are to your liking, tighten the lid and put the jar in the fridge. The lactobacillus will go dormant or slow down in the cold environment. You can store it there for many more months. The National Center for Food Preservation has recommendations for storage, water bath canning and other preservation methods. I cannot recommend dates or methods outside of their guidelines, but many fermenters have their own personal methods.
Here’s a little reference material:
Sandor Katz’s Wild Fermentation: The Flavor, Nutrition, and Craft of Live-Culture Foods is considered one of the best resources with recipes, stories and history. Great for beginners. For more history and culture, check out his The Art of Fermentation.
Facebook groups Wild Fermentation and The Cult of Pre-Pasteurian Preservation and Food Preparation