A General Guide To Fermenting


What do bread, beer, wine, spirits, yogurt, sourdough waffles, vinegar, kosher dill pickles, cheese, olives, and sauerkraut have in common? Yes, they’re all fermented foods and they’re all a result of a happy accident that occurred thousands of years ago and spread to nearly every culture on the planet. In fact, beginning with this chapter and continuing on through the end of this book, we’ll see how coincidence and serendipity combined to produce some of our favorite preserved foods.

Origins of Fermentation

The discovery of fermentation was probably accidental, at least as far as food was concerned. Scientists believe that as far back as 10,000 BCE, people were drinking the fermented milk of camels, goats, sheep, and cattle in North African regions. This was probably a naturally fermented product. The microorganisms (a form of lactic acid) in the milk plus the extremely hot daytime temperatures turned the bags of goat milk tied to the camels’ backs into yogurt.

Later, somebody somewhere in a more temperate climate left the grape juice out and it changed. It acidified but kept a certain tangy sweetness. It had fermented. And thus wine was born.

The next great leap forward probably happened when someone left the apple juice out. Later, it became apparent that it had also changed.

Perhaps someone dropped a piece of food, perhaps a cucumber, into a vat and left it there for someone else to fish out. When the person did, they noticed it had changed too. It hadn’t spoiled and even had a nice crunch. It was the first pickle.

Regardless of its beginnings, fermentation has become a staple of food preservation.

The Science of Fermentation

Fermentation is a natural process by which fruits, milk, and grains change their chemical composition by converting sugar to carbon dioxide and alcohol in the absence of air (an anaerobic environment). Fermentation preserves foods by making them so acidic that undesirable microorganisms can’t grow and spoil the food being fermented. As a science, fermentation earned the name zymology back in 1856, when Louis Pasteur was studying the role of yeasts in fermentation. Other scientists built on his work— and the rest, as they say, is history.

The basics of fermentation involve encouraging the good microbes to propagate and discouraging the undesirable microbes from contaminating the food. It’s a delicate balance, and indeed, fermentation has been called controlled rot. It’s not a very appetizing term, but it’s correct. Fermented food isn’t rotten, but it’s definitely not fresh. It’s an acquired taste.

There are two main avenues for fermentation:

  • The first is natural fermentation, where the microorganisms are naturally present, as we find with sauerkraut and kimchi and our earlier illustration of the goat milk turned to yogurt.
  • The second has the appealing name of backslopping. This is how we replenish a sourdough starter, for example. We add a bit of what was previously fermented to the food we wish to ferment.

One subtopic of science is health and some have made claims that the probiotics found in the fermentation process (lactobacillus) have benefits for digestive health. The science is still out on this and studies are ongoing.

General Procedures

If you’d like to try your hand at fermenting foods, we’ll take a look at the most popular candidates. Let’s start with pickles!

To make a good-quality fermented pickle, it’s absolutely essential to follow a tested and approved recipe to the letter. If you don’t take shortcuts with the process, you’ll be well rewarded for your time and effort.

Time is a crucial ingredient with fermented pickles and they can take from 4 to 6 weeks to arrive at the proper degree of readiness. During that time, you can’t ignore them or neglect them, so be sure to start them when you can supervise their progress.

During that 4- to 6-week time slot, the pickles will be immersed in brine. They’re not just hanging around though. Important bacterial action is taking place just below the water line. The bacteria in question are lactic acid bacteria and they’re found naturally on cucumbers. Fermentation encourages their growth as they work to preserve cucumbers by lowering their pH level to less than 4.0. This level indicates an acidic food, if you remember its importance from our section on canning. In addition to their efforts in lowering the pH level, lactic acid bacteria give fermented pickles their characteristic taste.

A stoneware crock is the traditional vessel for fermenting. Check to make sure the crock is free of chips and cracks that could allow the liquid to seep through. If you find some damage, you can line the crock with a heavy, food-grade piece of plastic and secure it around the rim.

If you don’t have a crock, food-grade plastic containers work well. Many fast-food restaurants or bakeries will let you buy or beg some.

Brine Basics

Each recipe will give you specific directions as to the amounts of ingredients to use in making the brine, including water. Hard water can cause the brine to become cloudy, but if you don’t have soft water, you can boil hard water and then let it sit for 24 hours. If any scum forms, skim this off. Also, as you take water from the saucepan to make the brine, don’t disturb the sediment on the bottom of the saucepan.

Brine Maintenance

This includes monitoring the temperature. You want the temperature to remain constant within the ideal range of 65°F to 80°F (16°C to 27°C). If the temperature gets colder or hotter than this, pickles will either spoil or be of poor quality.

Removing the scum that forms on top of the crock during fermentation is a daily task. This scum is made up of yeasts and molds that feed on lactic acid and produce enzymes that make the pickles soft. Without sufficient lactic acid, the pickles will spoil, so keep your crock scum-free.

Brine Bubbles

It’s alive! It truly is. The bubbles that rise to the surface of the brine tell you that fermentation is happening. When the process is complete, the bubbles stop. Check the pickles at this time. Take a cucumber out of the crock and slice it in half. There should be no visible rings or white spots.

You’ll probably see that the brine has become cloudy. This is because of bacterial growth that occurs during the fermentation process. Carefully pour the brine through a strainer and into a large pot. Heat the brine to boiling and reserve it to use in covering the pickles after you pack them into jars.

Fermenting by the Numbers

Two rustic jars of preserves on blue background

There’s a logical sequence to the fermentation process. It takes several days, but the steps are always the same. You should see the following:

  • Clear brine for the first 1 to 3 days
  • Cloudy brine and gas bubbles the next 2 to 3 days
  • Cloudy brine and no gas bubbles for 5 to 6 days
  • Finished (10 to 12 days from the beginning)
  • Before packing the pickles, check to be sure they’re perfect. They should be firm, crisp, and have good color. If you detect any signs of spoilage—soft, slippery, stinky, a strange color—don’t eat them. Dispose of them. Get informed about pickling, relish, & fermenting basics.

Fermented Dill Pickles

The following procedures are from the USDA’s Complete Guide to Home Canning. (See Appendix F.) This is an example of using a tested and approved recipe—something the home food preserver should always do!

You’ll need the following ingredients to make 4 pounds (1.8kg) of pickles:

  • 4 pounds (1.8kg) of 4-inch (10cm) pickling cucumbers
  • 2 tablespoons dill seed (or use 4 to 5 heads of fresh or dry dill weed)
  • ½ cup kosher salt
  • ¼ cup 5% distilled white vinegar
  • 8 cups water

Those are the basics. You can then add one or more of the following ingredients:

  • 2 garlic cloves
  • 2 dried red bell peppers
  • 2 teaspoons whole mixed pickling spices

Here’s the general method:

  • Wash the cucumbers and cut 1/16 inch (0.20cm) from the blossom end and discard. (This end contains enzymes that can cause soft pickles.) Leave ¼ inch (0.5cm) of the stem attached.
  • Place half the dill and half the spices in the bottom of a stoneware crock or other suitable container. Then add the cucumbers and the rest of the dill and the spices.
    Dissolve the salt in the vinegar and water. Pour this over the cucumbers.
  • Add a weight (such as a dinner plate weighted down with a leak-proof plastic bag filled with water and securely tied) and drape a clean cloth over the top of the crock to keep out dust or insects.
  • Place the crock where the temperature will remain between 70°F and 75°F (21°C to 24°C) for the 3 to 4 weeks it will take for the fermentation process to complete. Cooler temperatures will slow down the fermentation process and higher temperatures will cause the pickles to become soft.

If possible, have the crock already in the place where you’ll be keeping it during fermentation. This saves wear and tear on your back trying to lift it and avoids spills.

Check on the pickles every day if you can, but be sure to check on them at least several times a week. Remove any surface scum that forms. If the pickles become soft, slimy, or begin to smell bad, dispose of them and abort the mission.

When fermentation is complete, you can continue to store the pickles in the original container in the refrigerator if it will fit. You’ll still need to check in on it and remove any mold or scum that develops on the surface. If that seems less than satisfactory, canning the pickles is the way to go.

To process the pickles, pour the brine into a large saucepan on the stovetop over medium heat and slowly bring it to a boil. Reduce the heat to low and simmer for 5 minutes. Pack the pickles into jars and cover them with hot brine, leaving ½ inch (1.25cm) of headspace. Wipe the rims, adjust the lids, and process the jars in a boiling water bath for 10 minutes for pints and 15 minutes for quarts.

These pickles might also be processed by low temperature pasteurization. See Chapter 13 for specific instructions for this method. Also see Chapter 13 for troubleshooting fermented pickles.


Homemade tomato sauce in jars on wooden surface

Cabbage originated in Asia but made an early entrance into Europe. If you remember your grade school geography and the list of explorers you needed to memorize, you’ll remember Jacques Cartier. His significance to the home food preserver is his introduction of cabbage to the new world.

Cabbage grows well in many climates and keeps well over the winter. It’s not surprising, then, that people decided it would be a good candidate for fermenting. The result is a food that’s known and loved in cultures around the world.

Although fermented cabbage has its origins in Asia, the word “sauerkraut” is German: sauer meaning sour and kraut meaning cabbage. It’s a staple in most German households and a favorite of many folks of German descent. If you’re of German descent, you probably consider sauerkraut to be a vegetable and you probably slap some butter on it after it’s heated on the stove.

If the farmers’ market has a good supply of cabbage or if you’ve grown your own cabbage crop and have root cellared all you’ll need over the winter and still have some heads to spare, try your hand at making sauerkraut. Select firm, large heads of cabbage.

You’ll need the following ingredients:

  • 25 pounds (11.3kg) of cabbage
  • ¾ cup pickling or kosher salt
  • You’ll get about 9 quarts of sauerkraut from 25 pounds (11.3kg) of cabbage, but the actual amount depends on how finely you shred the cabbage and how small the core is.

Wash the cabbage and remove the outer leaves and any other damaged leaves. Cut the cabbage in half and then quarter it. Remove the core. Treat the cabbage gently. It might look like a tough vegetable, but if the leaves get bruised, the sauerkraut will suffer. This starts a chain reaction that will spoil the kraut:

  • Bruised portions tend to pack together.
  • This keeps the brine from being able to penetrate thoroughly.
  • Unbrined cabbage spoils or doesn’t ferment evenly and the sauerkraut is a bust.
  • How finely should you shred the cabbage? Not too coarse and not too fine. Aim for about ¼ inch (0.5cm) thick. This will usually be the coarse blade on your vegetable shredder or food processor.

The traditional vessel for making sauerkraut is a big stoneware crock. You can also use glass, enamel, or food-grade plastic containers. Garbage cans or non-food-grade plastic containers might react with the acid produced during fermentation and might make the sauerkraut unsafe to eat or give it a bad flavor.

You’ll need to do some serious eyeballing to make sure the crock is deep enough to hold all the shredded cabbage and brine and still leave 4 to 5 inches (10 to 13cm) of space below the rim. Why so much space? During fermenting, gas bubbles will rise. If there’s not enough room, the brine will bubble over and you’ll have a major science experiment in the kitchen or wherever you’ve placed the crock.

The procedure for making sauerkraut is called dry salting. Place the shredded cabbage in the crock and add 3 tablespoons of kosher salt. Mix thoroughly with clean hands and then pack the cabbage down firmly into the container. This is your first layer. Repeat this procedure with the next 5 pounds (2.3kg) of cabbage and continue the layering until all the cabbage and salt is in the crock. A concentrated brine forms when the salt leaches moisture out of the cabbage.

The brine will form fairly quickly. If it hasn’t completely covered the cabbage within 1 hour, add some prepared brine to the crock. Add 1½ tablespoons of kosher salt to 1 quart of water, heat to boiling, and cool. Make as many quarts as you need to get the job done.

Place a plate on top of the cabbage to weigh it down under the brine. Add a weight to the top of the plate if needed and cover everything with a clean, heavy cloth (a bath towel works well). Check the brine frequently—once a day is recommended—and remove any scum that forms.

You can also use a brine-filled bag to weight down the cabbage. If you go this route, don’t lift the bag out of the crock until the bubbling has stopped and fermentation has completed. Place a 2-gallon food-grade plastic bag inside another. Fill with brine made from adding 1½ tablespoons of kosher salt to 1 quart of water. Tie securely. You’ll need about 3 quarts of brine for a 5-gallon crock.

Now it’s time to have some faith. You’ll need it during the first week because the fermenting cabbage frequently produces a horrific odor. Don’t despair, as this is normal and will go away as the fermentation process continues. (Although it’s probably a good reason not to keep the crock in the kitchen or any other room you need to visit frequently.)

If you keep the temperature between 70°F and 75°F (21°C to 24°C), the sauerkraut will be fermented in 3 to 4 weeks. Then it’s ready for eating, canning, or storage in the refrigerator. (It will keep for several months there.)

For canning, you can choose either hot pack or raw pack:

  • Hot pack: Place the kraut and brine in a large pot, turn the heat on high, and bring to a boil. Stir frequently to be sure the entire batch is hot throughout. Then pack it firmly into jars and add brine to cover, leaving ½ inch (1.25cm) of headspace. Process in a boiling water canner for 10 minutes for pints and 15 minutes for quarts.
  • Raw pack: Pack the kraut firmly into jars and cover with the brine, leaving ½ inch (1.25cm) of headspace. Process in a boiling water canner for 20 minutes for pints and 25 minutes for quarts.

Troubleshooting Sauerkraut

You know you did everything by the book. Well, almost everything. Surely there’s some leeway in the directions? It shouldn’t matter if you changed the ingredients or the temperature or took some shortcuts. Right?

Wrong, unfortunately. When you’re dealing with fermentation, everything has got to be just right, and even then, it might seem the fates are conspiring against you. Here are some common problems, along with their possible causes and recommended solutions:

  • The sauerkraut is really dark: This can have several causes: using iodized salt, not mixing the salt into the cabbage thoroughly, having the temperature too high during fermenting or storage, or not cleaning and trimming the cabbage properly as you began. The solutions are found in the causes. Follow the directions carefully.
  • The sauerkraut is soft and mushy: Again, salt is the culprit—too little or not mixed in well enough. The temperature might also be too high. If you didn’t pack the cabbage firmly into the crock, air pockets can form and play havoc with the fermentation process. Use the amount of salt called for and mix it in thoroughly as you’re preparing the layers in the crock. Pack the cabbage firmly and be sure to store the crock in a location where the temperature won’t soar into the danger zone.
  • There’s a white scummy surface on top of the brine: Air got in because the weight didn’t weigh enough to keep it out. If the plate’s not heavy enough, add bags full of brine. You can skim off the scum. The kraut should be fine.
  • There’s a moldy surface on top of the brine: The temperature got too warm during the fermentation process and/or the crock wasn’t covered well enough to keep out the air. This one isn’t a keeper. Discard the sauerkraut. It’s potentially unsafe to eat. Next time, keep the crock in the 70°F to 75°F (21°C to 24°C) zone and covered to exclude air.
  • The kraut is rotten: The same conditions that cause mold to grow on the surface can cause the kraut to go bad. Keep the temperature in the 70°F to 75°F (21°C to 24°C) zone and keep the crock covered to exclude air. Dispose of the kraut. It’s bad.
  • The kraut is slimy: This points to too little salt and too high a temperature during the fermenting process. Discard. Next time be scrupulous about the correct amount of salt and the proper temperature range.

As you can see, operator error is usually the culprit. Because you’re only dealing with two ingredients (cabbage and salt), the right proportions are essential to get a good result. If you read the directions carefully before you begin and keep tabs on the temperature during fermenting, the sauerkraut should turn out great. Learn more about self-brining ferments of sauerkraut.


If you’re a bit intimidated by the steps involved in making fermented pickles or sauerkraut, you can purchase a yogurt maker for around $40 or use the yogurt function on your Instant Pot. It’s practically painless and you can find numerous recipes online or consult the instruction book that came with your appliances. Yogurt is one fermented food that needs the backslop—that’s the starter.

Sourdough Starter

Sourdough is interesting in that it adapts to its environment. If you borrow some starter from a friend in the wilds of Montana, it’s going to change to fit in to its new home in California. That’s the nature of the yeast. If you’ve begged some starter, you’re all ready to go. Just remember to replace what you’ve taken out each time you use it. Instructions follow. If you need to make yours from scratch, here’s how.

All you’ll need are equal parts all-purpose flour and water. That’s it. The yeasts present in the flour will get to work as soon as they’ve had a drink. You’ll mix an equal amount of flour and water by weight every day for 1 week and add it to the mix. After that, it will be ready to use.


  • All-purpose flour
  • Water
  • A glass or food-safe plastic gallon jar
  • Scales
  • Measuring cups
  • Spoon

Each day, combine 4oz (120g) flour and 4oz (120g) water by weight. Add to the jar and mix thoroughly. Place the lid on the jar or place plastic wrap over the top of the jar. Set the jar in a warm place in the kitchen where it won’t be disturbed. Starter likes even, warm temperatures.

For the rest of the week, continue to add the same proportions of flour and water to the jar each day, stirring completely. This is called feeding. The mixture will begin to have bubbles and take on a ropy texture. It will also take on a sour odor. This is good. You’re making sourdough starter. When it’s nice and bubbly and sour and ropy, it’s ready to use. Just scoop out what you need and don’t let your jar get too low. Continue to replace what you’ve taken out the same way you built it in the first place.

Leave a Reply

Your email address will not be published. Required fields are marked *