How much salt to use when fermenting food is a fundamental question. We are here to answer this… with science! Thanks to microbiology, we now know what is safe when fermenting vegetables. We know the best salt to use for fermentation, how much salt to use when fermenting vegetables, and how long you should ferment foods. Learn fermentation science with us!
Everything You need to Know About Salt and Fermenting Vegetables
If you really think about it…WE are not fermenting vegetables, the MICROBES are fermenting vegetables. We just have to set them up for success and watch it happen.
Fermentation is an ancient way of preserving foods. We know people have been fermenting without a background in microbiology for thousands of years. We definitely aren’t the first people to do it, and we are not the first people to do it “right”. There are many ways in which humans of the world ferment foods. Whether in wooden barrels, in a hole in the ground, in crocks, in glass jars… fermentation methods are eclectic and fascinating.
We love to learn about traditional fermentation methods. After all, we have to understand where the practice comes from. But there are a lot of irresponsibly culturally appropriated and Americanized fermentation recipes out there, that are giving fermentation a bad reputation in the USA. Because of these recipes, people get nasty and bad results. These recipes leave people confused, feeling like they are missing a piece of the fermentation puzzle. People feel like they fail at fermentation because the recipes do not produce consistent results. People eat ferments that are not made properly and it leads to stomach aches, hives, itchy eyes. These inaccurate recipes are tarnishing the good name of fermentation.
Natural fermentation precedes human history, I know. Since ancient times, humans have exploited the fermentation process. I think it’s only reasonable that, in our modern times, we allow ourselves the space to respect and learn about the microbes of fermentation. We should choose to understand microbes to harness fermentation in the healthiest way possible. Also, let’s not irresponsibly culturally appropriate recipes and instead bring pride and respect to the long-standing culture of fermented foods by understanding the process fully.
If you want to make traditional fermentation recipes from other cultures, some of which have quick fermentation times and high salt concentrations, find a teacher from that culture who provides recipes (there are so many) and follow EVERY step, method, temperature, time, and ingredient. These types of recipes are time-tested and perfected over thousands of years.
How Much Salt Should You Use to Ferment Foods?
Check out The Complete Guide to Safely Using Salt in Vegetable Fermentation to learn about different salt concentrations for different vegetables.
The salt concentration is the first step in establishing a safe fermentation environment. Particular concentrations of salt pave the way for creating a happy home for lactic acid-producing bacteria. These bacteria are species of Leuconostoc and Lactobacillus. It isn’t about how salty or not salty you like your fermented vegetables. It is about the home you are supposed to create in order for these beneficial bacteria to thrive. All the microbes needed for the fermentation process to start are already present on your vegetables, even after you wash them. Once you provide the proper salt concentration, bacterial succession can occur and lactic acid can be adequately produced.
So How Do We Measure Salt in Fermentation?
In order to use a precise and accurate salt concentration, you must use units of mass to measure your salt. There are two mathematical ways to create an exact percent salt concentration, and the desired salt concentration varies by type of vegetable. You can see recommended salt concentrations in our blog The Complete Guide to Safely Using Salt in Vegetable Fermentation. Next, I will use 2.5% as an example.
Creating a 2.5% total salt concentration:
To create an exact 2.5% total salt concentration place a bowl on a scale and tare/zero the scale. Add 2.5 grams of salt to the bowl, then add your produce and any water into that same bowl up to 100 grams. That’s a 2.5% total salt concentration.
What we do is slightly different and easier: We weigh all of our produce and water, multiply that weight by 2.5%, and add the number we get in salt. This results in an approximate 2.5% salt concentration that is perfectly safe and optimal for fermentation.
If we have 100 grams of produce and water, we multiply by 2.5%. So 100 x 0.025 (you have to move the decimal because you are multiplying by a percentage) = 2.5. So we add 2.5 grams of salt. This ends up being a 2.44% total salt concentration.
In order to calculate a total percent salt concentration of the mixture you divide the grams of salt by the total grams of the whole mixture: 2.5 grams of salt / 102.5 grams (of salt + water + produce) = 0.02439.
Move the decimal to make it a percent and you get 2.44% And guess what? With this method, we end up with 2.44% salt, no matter the weight of vegetables or water… if we add 2.5% salt, the resulting total salt concentration will always be 2.44%
For example, If we have 756 grams of cabbage and water, we multiply that by 2.5%. That equals 18.9. So we add 18.9 grams of salt.
18.9 / (756+18.9) = 0.02439
Yep. That’s 2.44%
The only way you will get a consistent salt concentration throughout different batches of fermentation is by weighing the produce and water, doing math, and then weighing out your salt.
Reasons to weigh everything and do the math to determine salt concentration:
1. Between batches and throughout the seasons, the weight of vegetables you are fermenting will vary and majority of the mass of most vegetables is water.
2. Sodium chloride (aka NaCl aka Salt) is an ionic compound with a mass…therefore, total salt concentration can only be determined by weighing the salt. Depending on what brand, style, and type of salt you are using the amount of NaCl in a volume measurement, such as a tablespoon, varies greatly.
Unrefined sea salt can be found in many different “grains”, such as flake, large grain, small grain, etc. A teaspoon of flake salt has a mass of about 1 gram. A teaspoon of small-grain Himalayan salt has a mass of about 3 grams. If you added the teaspoon of flake salt to 100 grams of vegetables and water you get a 0.99% salt concentration. If you add the teaspoon of Himalayan salt to 100 grams of vegetables and water you get a 2.9% salt concentration. That’s a huge difference, and the 0.99% salt concentration is completely unsafe, and probably won’t select for probiotic microbes to thrive.
Common Questions About Measuring Salt in Vegetable Fermentation:
- Why weigh the vegetables? All vegetables are at least 93-98% water, so you have to account for the water inside of the vegetables contributing to water activity. Because of osmosis and concentration gradients, the total salt concentration includes the water found in the vegetables.
- They didn’t need math to ferment 2000 years ago. This is more of an argument than a question… “They” also lived in a less toxic world where agriculture was different, salt was different, microbes were different and antibiotic-resistant bacteria didn’t exist. No, people didn’t always use science to ferment… but they have used weight measurements for recipes, trade, and calculations for a LONG time. A long time meaning since around 1200 BC at least. People of the Eastern world used mass and ratios (aka math) to make fermented vegetables for thousands of years. Not American tablespoons. Traditionally, in the eastern world, fermented vegetables are made with high salt concentrations between 5% and 20%.
No matter what salt concentration you use, the concentration of salt in vegetable fermentation can only be determined using the mass of the salt, and the mass of the total mixture. One tablespoon of two different types of salt will have two different masses, so there is no possible way to achieve the desired salt concentration by using arbitrary amounts like a head of cabbage and a tablespoon of salt… and you definitely cannot estimate a salt concentration by salting to taste. Taste is arbitrary and salt perception is vastly different for each person depending on diet and lifestyle.
So when someone tells you that they saw a Korean grandma or an old German lady “eyeball” amounts to make fermented kimchi or sauerkraut, those old women with family recipes are eyeballing a weight of cabbage and a weight of salt. They are not eyeballing a fluid ounce/volume measurement such as tablespoons. I have been making sauerkraut and kimchi on a large scale for almost four years now. I know exactly what 600 pounds of shredded cabbage looks like and what 2,024 grams of the same sea salt I’ve used for four years looks like. So I can “eyeball” a recipe too, but my guesstimates are visually based upon mass.
Other Fermentation Factors
Accurate salt concentration, providing adequate time for the fermentation to proceed, and proper temperature are necessary for a healthy population of microbes to develop in vegetable fermentation.
The temperature for vegetable fermentation should be between 70-80 degrees F. However, anywhere between 60 and 90° F is acceptable. The cooler the temp, the slower the fermentation. The hotter the temp, the faster.
Once the temperature is established the two main factors that need to be tailored to the microbes are salt concentration and length of time for the fermentation. If all of these things are accounted for appropriately, the pH of the fermentation will drop, lactic acid will build up, the microbial population will consist only of probiotic bacteria, and the vegetable matter will be preserved.
Are you interested in safely fermenting foods at home?
Try out these recipes:
- Roasted Garlic Sauerkraut with Black Pepper
- Fermented Beet and Red Cabbage Sauerkraut
- Fermented Dill Pickles
Frias, Juana & Martinez-Villaluenga, Cristina & Peñas, Elena. (2016). Fermented Foods in Health and Disease Prevention.