Six Ways to Optimize Food Safety for Fermented Vegetables

by Kaitlynn Fenley

Food safety for fermented vegetables is simple and easy to practice. All fermented vegetables can have different microbiome compositions based on multiple variables. This means that all fermented vegetables can have different microbial-synthesized byproducts (beneficial postbiotics) based on the same multiple variables. Think of fermentation as a countertop science experiment. That’s what it is! A food science, food microbiology experiment. In every science experiment, there are independent and dependent variables. Let’s explore how these variables influence fermentation.

Food Safety for Fermented Vegetables is Basic Science

The potential of lactic acid fermentation to control the harmful effects of food contamination depends on multiple, controllable variables.  Have you ever learned about variables in simple science experiments? Let’s review:

  • An independent variable is a variable that is changed or controlled in a scientific experiment to test its effects on the dependent variable. 
  • A dependent variable is a variable being tested and measured in an experiment.

Variables in Vegetables Fermentation

In a vegetable fermentation experiment we have something that resembles a dependent variable: The final microbial composition and the byproducts those microbes produce in the fermented foods.

There are SIX main factors here that we can look at as independent variables. As these independent variables change the dependent variable (the microbial composition and microbial produced postbiotics in the final product) will change.

  1. Substrate: What vegetable is being used? What’s the available sugar content? What’s the vegetable’s microbiome composition? What other ingredients are included? Are there any protein-rich animal-based ingredients in the recipe? These substrate variations can influence which microbes grow and which nutrients are available for microbes to metabolize into other compounds. 
  2. Salt Concentration: The salt concentration determines which groups of microorganisms thrive first in fermented vegetables, thus influencing pH, oxygen levels, and which microbes can thrive after fermentation.
  3. Fermentation Time: Bacterial succession and microbial metabolism in fermentation take time. How long fermentation occurs impacts if GABA, melatonin,  Phenolic compounds, exopolysaccharides, and beneficial bioactive peptides are produced or not.
  4. Temperature: Too low temperatures can inhibit vegetable fermentation, too high temperatures can ruin the flavor and texture. In some cultures, traditional fermentation recipes include sugar and are fermented at ambient temperatures ranging from 80-90° F, making fermentation quite fast.
  5. Oxygen: Certain microbes love oxygen, certain microbes love anaerobic environments. Oxygen levels directly influence which microbes thrive. Everything has to stay submerged in the liquid while fermenting, or in an air-tight container like a fermentation crock.
  6. Acidity: Some microbes love acid, some microbes die in acid: the initial pH and a progressive drop in pH of fermented vegetable influences which microorganisms grow. Adding citrus juice (citric acid) at the start of fermentation can help to control unwanted microbial growth in the initial fermentation stages. 

Six Ways to Optimize Food Safety for Fermented Vegetables 

Food safety in fermentation means controlling these independent variables to ensure the best microbial composition; thus, the best microbial byproducts produced. Therefore, when we do not control the variables, a lot of things can happen. 

1. Substrate

Just like eating many different vegetables influences the composition of your microbiome, fermenting different vegetables changes the structure of the microbial fermentation community. Vegetables & fruits with ample sugars, for instance, can encourage yeasts to thrive, leading to excess alcohol production and possible acid metabolism by yeats. Sometimes this can negate the preservative effects of pH decrease. Including animal products in fermentation, like whey and fish paste, can lead to microbial-produced biogenic amines. This can cause histamine reactions for some people when consumed. 

I stick to vegan fermented vegetables only, and if I use fruit in fermented vegetables the fruit does not make up more than 1/4 of the ingredients.

2. Total Salt Concentration

Not using the proper salt concentration is a major cause of concern. Salt concentration controls initial microbial growth before lactic acid bacteria can produce acid to preserve the vegetables. Basically, salt roots for Leuconostoc bacteria to start thriving while discouraging yeasts, fungi, and potential pathogens from thriving. This leads to a quick and safe drop in pH.

An adequate salt concentration is vital and extremely effective in controlling dangerous fungi, gram-negative bacteria, and the toxins they can produce in fermentation. This is because specific salt concentrations encourage the growth of desirable, beneficial microorganisms that rapidly and steadily decrease the pH and preserve the vegetables. These species include Leuconostoc spp. and Lactobacillus spp.

If you’re looking for guidance on calculating and measuring salt concentrations you can reference The Complete Guide to Safely Using Salt in Vegetable Fermentation.

3. Time

Too short of a fermentation time robs you of so many beneficial postbiotic compounds. When given enough time, Lactobacillus spp. produce bioactive peptides and polyphenols that are wonderful for health. Lactobacillus only start to thrive, metabolize, and produce their byproducts after about 7-14 days of fermentation. So, being patient with fermentation projects is the way to go. Anything after seven days is probably okay to taste test, but I like my ferments right around 21-28 days for maximum health benefits and flavor.

Fermenting vegetables for a proper amount of time also influences biogenic amine (histamine) content. If Lactobacillus spp. are given enough time to thrive and then metabolize, a lot of these species have the ability to degrade and decrease biogenic amines in all types of fermented foods.

4. Temperature

Putting your fermentation projects in the fridge too early can lead to low acid production and not enough acid for proper preservation. On the other hand, fermenting at too high a temperature can cause spoilage microorganisms to thrive in excess in the first five days of fermentation, resulting in unpleasant flavors and poor sensory qualities. The ideal temperature for vegetable fermentation is between 60 and 90° F (absolute maximum). I like my fermentation temperature right at about 78 degrees F.

5. Oxygen

Fungi will find a way to grow if all ingredients are not submerged in the liquid during fermentation. Fungi do undesirable things in vegetable fermentation. Some fungi produce toxins, and some can metabolize acids, increasing the pH and negating the preservation effects of lactic acid fermentation. 

You can learn more about keeping fermented vegetables anaerobic here: How to Keep Fermented Foods Anaerobic

6. Acidity

The initial pH of fermented vegetables influences which microorganisms grow. Generally, an initial pH around 6 is a good place to start. Then, a steady decrease to more acidic conditions is vital. An anaerobic environment may not form if the fermented vegetables start too acidic. Using pH strips is a great way to monitor the changes in pH throughout fermentation.

You do not need to fear fermentation because it is SO easy to set the right microbes up for fermentation success. Thus, it’s so easy to create healthy and perfectly safe fermented vegetables at home every single time!

an open jar of roasted garlic and black pepper sauerkraut.

Food Safety for Fermented Vegetables is Easy! 

What if I told you that literally all you have to do is weigh your ingredients when fermenting, and keep everything submerged in the brine? That’s it.

All you need is:

VIOLA! Perfect microbes and perfect ferments every time. 

Food Safety for Fermented Vegetables Makes Sense

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.

Some traditional fermented foods, like Baechu Korean kimchi and Dưa Chua Vietnamese fermented vegetables have a swift fermentation time. This is thanks to specific ingredients, variables and traditional methods.

Dưa Chua, for instance, is made by drying vegetables in the sun then submerging them in a brine that includes salt and sugar. Dưa Chua is usually fermented for about 4 days at 80-95° F.

Baechu Korean kimchi is made by soaking nappa cabbage in a high salinity brine for 12 hours before it is rinsed and rubbed with a paste made of salted shrimp, fish paste, gochugaru, sugar, ginger, garlic, and scallions. Then it is packed into an air tight fermentation crock and enjoyed after only three days of fermentation.

In both of these examples, the ingredients, methods, and temperature are very important factors influencing the fermentation time. If you want to make traditional fermentation recipes from other cultures, some of which have quick fermentation times, 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.

fermented zucchini in a mason jar.

Easy Fermented Foods Recipes

Do you want to learn how to calculate salt concentration for your own recipes? Visit our The Complete Guide to Safely Using Salt in Vegetable Fermentation blog!

Wild Heirloom Culturing

This is a different fermentation method I came up with to ferment vegetables that normally do not ferment well using traditional wild fermentation techniques. We have a few recipes that use this method:



Toxins in Fermented Foods: Prevalence and Preventions

Effects of different types of salts on the growth of lactic acid bacteria and yeasts during kimchi fermentation

Effect of salt concentration on microbial communities, physicochemical properties, and metabolite profile during spontaneous fermentation of Chinese northeast sauerkraut

Establishment Limitation Constrains the Abundance of Lactic Acid Bacteria in the Napa Cabbage Phyllosphere

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Leave a Comment


gary August 9, 2020 - 11:58 am

is there a certain type of salt to be used when fermenting food

Kaitlynn Fenley August 9, 2020 - 1:26 pm

I like to use solar evaporated, unrefined sea salt. Any salt will work though, as long as you weigh the salt to measure it. 🙂