Fermenting Vegetables

One third of the foods in the average diet are fermented by our wonderful microbial friends! Fermentation has been around forever, but long ago it was probably just thought of as a magical occurrence. A lot of things are/can be fermented, and it's particularly easy to ferment vegetables at home! Fermenting veggies is a great way to spice up recipes and add probiotics to your diet. It's also a greatly nutritious preservation method to waste less produce! Fermented vegetables are packed not only with probiotics, but also with essential vitamins, nutrients, minerals and prebiotics necessary for health and wellness. 

We ferment whatever is in season from the local farmers market. We also grow a few vegetables on our apartment patio. When we can't eat our produce fast enough, fermentation is our favorite way to preserve for later.  Our vegetable ferments are made solely with salt, vegetables, seasoning and sometimes saltwater brine (don't worry! we talk about brines in detail below). We are microbiologists, and we use science to ferment! All of our ferments are checked under the microscope bi-weekly to see what stage they are in. This allows us to include approximate, recipe specific fermentation timelines in all of our fermentation blog posts, helping keep you and your ferments healthy! 

The Science of Fermenting


What Is Fermentation? 

When we talk about fermenting vegetables, we are specifically referring to a microbial process called lactic acid fermentation. This particular fermentation occurs when certain bacteria produce lactic acid as a by product of fermenting plant sugars for energy. All it takes is the addition of salt to your vegetables, and you can make something quite amazing happen!

Particular concentrations of salt pave the way for creating a happy home for lactic acid bacteria. All the microbes needed to get the fermentation process started are already on your vegetables, even after you wash them. For the best probiotic microbes to thrive and produce lactic acid, the substance that actually preserves the vegetables, we harness the delicate process of bacterial succession. Bacterial Succession is when the growth and metabolism of one bacterial species increases, permanently altering the environment. This leads to the death of that species and the take over of a different type of bacteria. As one type of bacteria dies off, the next species takes over until the ferment reaches a point with perfect living conditions for species of Lactobacillus (which are the probiotic microbes). 

When using wild natural microbes to produce fermented foods, bacterial succession takes time and occurs in three stages that take 3 1/2 weeks.  We call them the three microbial stages of fermentation.   

Bacterial succession and the stages of fermentation make foods safe, delicious and nutritious! With the addition of salt bacterial succession begins, next an anaerobic environment is created, then the production of lactic acid can occur.  Once in stage there there is a very selective environment within the fermentation vessel, where only probiotic bacteria can thrive; bad microbes have already died off and are inhibited from growing.  

Stage one: Stage one of microbial fermentation begins as soon as you add the salt to your veggies. There are many bacteria naturally on your vegetables that can tolerate salt, and the ones that utilize oxygen proliferate first. In this stage it's the Gram-negative rod shaped species of bacteria, like Enterobacter cloacae and Erwinia herbicola, that thrive. In the brine-vegetable mixture, these bacteria use up all the oxygen present and make the brine into an anaerobic (oxygen free) environment. Once all the oxygen is used up by the stage one microbes, and the brine is a nice anaerobic environment, we enter into stage two.

Stage Two: The second stage begins about two or three days past the start of fermentation.  At this time the stage one bacteria have died off, and Leuconostoc species of bacteria populate. Leuconostoc species are lactic acid bacteria that tolerate salt and acid. They are Gram-positive cocci shaped, heterolactic fermenters (heterolactic means that they produce two different acids.) Lactic acid, ethanol and carbon dioxide along with small amounts of acetic acid and glycerol are produced when these bacteria thrive. This is the bubbly stage! At the time for stage two you want to look for bubbles from the carbon dioxide being produced (be sure to burp the fermentation jar during this stage). In stage two the environment becomes more acidic, leading us into stage three. 

Stage Three: This stage begins after about six to eight days from the start of fermentation. The bacterial population mostly consists of Lactobacillus species in stage three. Lactobacillus species are salt-tolerant, acid-tolerant, homolactic fermenters. They are considered homolactic fermenters because the one main product from their fermentation of plant sugar is lactic acid. Their metabolism of plant sugar into lactic acid results in a acidic pH of about 3.1 - 3.7. The lactic acid produced in this stage is actually what preserves the ferments. Once stage three is reached you want to give your ferments time to be in stage three for a bit, so that the lactic acid bacteria have adequate time to produce their wonderful preserving substance!  We always wait about two weeks after this stage is reached, because that time yields a safe pH and a  perfectly pleasant sour taste. It is okay to vary this time just a bit though. It is fine to taste test, refrigerate and eat at about 12 days past reaching stage three, (which would be around three weeks total time).


A couple of important factors influence the creation of a perfect fermentation environment, though. First, to reach stage three and to prevent unwanted microbes in your ferments, vegetables MUST stay in an anaerobic environment; you must keep the produce you are fermenting submerged in the anoxic brine created in stage one. Using a fermentation weight is best to accomplish this. You also should keep your ferments at a favorable temperature of 21-24 degrees C (about 71-75 degrees F) and not in the sunlight. Lastly a steadily decreasing pH is needed, ph strips are great for checking the progress of pH as your ferments move through the stages. 


To summarize: No, you do not need a fancy jar. NO, you absolutely do not need a starter culture for vegetable ferments. YES you can use a clean mason jar. YES, you should stock up on some quality sea salts! This is a science based blog, therefore we use the metric system in our recipes. We highly recommend investing in a kitchen scale that weighs in grams (amazon has some great, cheap options). 


Always use a high quality salt, such as Cultured Guru Fermentation salt.

Its important to remember that different  types of salts weigh different amounts, so using volume measurements like tablespoons or cups is very inaccurate. For example, a teaspoon of a flake salt weighs half as much as a teaspoon of small grain Himalayan salt. You must use mass to calculate a salt concentration.  A 1% salt difference is quite a lot to tiny microbes with delicate living parameters, so it is vital to weigh the salt to create the best fermented vegetables!  

Getting your Ferments Started


How you will add salt to your vegetables depends on what vegetable you are fermenting. One method is to weigh your vegetables and add 2.5% of that weight in salt. For example, If my cabbage weighs 2,000 grams (about 5 pounds) I would add 50 grams of salt, because 50 grams is 2.5 % of 2,000 grams. This method uses the salt to draw the water out of the vegetables and create a saltwater brine. Another method is to weigh the vegetables and add a precent of that weight in salt, and also add a premixed a saltwater solution of the same percentage to the vegetables. This method usually uses different concentrations of salt depending on what you are fermenting.  


Stay below the brine. There is a lot of talk on the internet about what jars and lids are truly air tight, and which ones really "keep oxygen out"... air tight lids are nice to have, but a jar with a proper fitting lid will do fine (such as a mason jar and matching mason jar lid). As far as lids go, you just want to prevent evaporation. Creating an anaerobic environment within the brine, and keeping your veggies submerged in that brine is what's most important. The best way to do this is by using a fermentation weight. Recall that in the first stage of microbial fermentation all the oxygen is depleted from the brine. This means that as long as you keep all the vegetables submerged within the anoxic brine in the jar, it's okay if your lid is not perfectly air tight; you will have a successful fermentation! 

Trust your senses. When your ferments reach the time for stage two, you should look for bubbles. At the proper time, this is the first indicator that your fermentation is on its way to success! Your sense of smell is your greatest ally in fermenting. Smells should be pleasantly sour, never pungent or repulsive. Your senses will let you know when something shouldn't be eaten, so trust your nose! If you do not know what raw fermented greatness smells like, then you can easily buy some of our delicious, raw sauerkraut to smell and eat! 

Be Patient. Our fermentation timelines are pretty accurate when you follow the recipe and the directions exactly. This means using the same ingredients, same supplies and keeping your ferments at the same temperature and light conditions will yield almost the same timeline for the stages of fermentation. If you vary the recipe that's fine too! Just be patient. If you have doubts that your ferments have made it to stage three and lingered there a bit, let them sit for a little longer time. A few extra days is better than too few days! 

Concentration is important. Don't just add more salt as a solution to a fermentation problem. It will not help. Salt concentration is very important to tiny microbes because their living parameters are delicate. If you are using the salt by weight brine method and are low on brine, try mixing your vegetables and salt by hand for a longer time in a bowl before adding to the jar. Be sure to pack the vegetables in the jar, using a spoon or tamper, to help draw out the water. You can also try grinding up a portion of the vegetable- salt mixture in a food processor/blender to release more water. Adding a heavier fermentation weight is also a good idea. 

Fungus among us or a funky smell.  If you have a fungus/ mold/ film/ stinky smell in your ferment, I'm sorry but you need to throw it out and start over. You cannot simply scrape off fungus. Just because you don't see it after scraping it out, doesn't mean it isn't there. fungus indicates that bacterial succession is not occurring properly. Repulsive smells are also definite indicator that something went wrong, and the ferment needs to be thrown away. If you have a curbside compost service or a personal compost bin, a great way to dispose of bad ferments is to compost them. Remember that your sense of smell is you number one sense in fermenting! Trust your nose! 


Peace, Love & Microbes,

Kaitlynn Fenley


- Fermentation involves various microorganisms and microbial communities. The recipes and information we provide are meant to keep you healthy and safe while fermenting at home. However, microbes are living organisms and are not always controllable or predictable. Use of our recipes and home fermentation advice is done at your own risk. -