Fermentation 101

Making sauerkraut.

Books upon books have been written about fermentation. This is by no means meant to be an exhaustive post on the subject; this is a basic overview of fermentation and the science/art (scart?) of fermenting.

I hope to lure you into the wonderful world of friendly bacteria and yeasts; let’s put these little microscopic critters to work!

Fermented honey garlic.


  • Fermentation – the process that takes place when we create an environment where bacteria and yeast that are good for our health can thrive. Lactobaccilli and yeast partially digest foods for us, which makes more phytonutrients bioavailable. Fermentation slows in cooler environments.
  • Salt – for our purposes, when I refer to salt for fermentation I mean salt with no iodine added. The more natural, the better. Canning or pickling salt will work. I prefer pink Himalayan salt.
  • Water – when I mention water for brine, I mean pure water. Distilled, filtered, or good spring water all work. Never use tap water from a municipal source; we don’t want chlorine in our ferments.
  • Brine – a combination of salt and water that is the medium for most of our ferments. Some “non”-brine ferments include honey fermentation or self brines. Salt-to-water percentages for safe brines range from 2-4% by weight. To calculate a 3% brine, multiply the weight of your water by .03. Add the product in weight of salt to the water and stir until dissolved. Pour that brine over what you intend to ferment. Make and add more brine if necessary.
  • Self brine – for these ferments, we use liquid from the vegetables and/or fruits we ferment for the water content. Examples include cabbage, peppers, lemons, or tomatoes. To calculate a safe percentage of salt to add, we weigh our vegetables and multiply their weight by 2-10% for the weight of salt to add. I add 2.5-3% salt by weight to cabbage for sauerkraut; I add 7-8% salt by weight to pepper mash.
  • Headspace – the space between the top of the ferment and bottom of the container lid. This space needs to be small (1/4 to one inch), as the presence of oxygen makes our ferments susceptible to mold growth. A healthy ferment produces CO2 that displaces oxygen in the headspace. Too small of a starting headspace, depending on the ferment, can result in the ferment expanding into an airlock and out of the container.
  • CO2 – active ferments produce carbon dioxide. This gas can be seen as bubbles rising through the fermentation medium. CO2 needs to be released, while oxygen needs to be kept out. That’s why we use airlocks or finger-tight lids. If using finger-tight lids, you need to “burp” the jar 1-2 times a day. Simply loosen the lid to the point it is almost completely loose, then finger-tighten it back again.
  • Yeast – wild yeast is present on all non-irradiated vegetables and fruits and in raw honey. Locally-grown produce with more local yeast might be best for us. However, most yeast/alcoholic ferments use store-bought yeast introduced for its characteristics. Special yeasts ferment faster, more effectively, withstand higher alcohol levels, and produce a better tasting product. The only yeast ferment I do for food is sourdough, which is a short 8-36 hour process.
  • Lactobaccilli – these bacteria are also present on non-irradiated produce and in raw honey. As with yeast, I also say the more local the better for bacteria for your gut health. Bacteria form colonies on produce, with many dominating and regressing in cycles depending on the acidity, temperature, and nutrient levels in ferments. The most useful for us are lactobaccilli. These bacteria produce lactic acid and give us common foods like yogurt, cheese, and sour cream.
  • Processing – processing ferments is necessary to stop the fermentation process and/or make some fermented foods ready to eat. Heating a ferment to 185* for ten minutes kills all bacteria. Vinegar, in the proper concentration, also stops fermentation. Some foods, like sauerkraut, I never process so I can get all the good bacteria for my gut!
Pressing juice as I prepare preserved lemons.

What you need:

  • Container – always use a glass, a ceramic, or a food grade, BPA-free plastic container for fermentation. NEVER USE METAL. Fermentation creates an acidic environment, and acid corrodes metal. If you only have metal lids for Mason jars, you can use them. However, keep the ferment from contacting the metal lids as much as possible. You can place a coffee filter between the ferment and the lid, but remove or replace it once it gets wet. I use Mason jars of all sizes, preferably wide-mouth, for my ferments. For larger ones, I prefer plastic buckets (food grade!).
  • Airlock – airlocks are designed to let gas escape from a ferment while keeping oxygen out. They are inexpensive and safer than a finger-tight lid, cheesecloth, latex glove, or other means. I have about a dozen.
  • Salt
  • Water
  • Produce – you can ferment just about anything: peppers, tomatoes, garlic, carrots, beans, cucumbers, okra, cabbage, lemons, ginger, mustard seeds, and honey are just a few!
  • A kitchen scale – I wholeheartedly recommend a digital scale that weighs in grams. They are inexpensive (<$20) and make successful ferments pretty much fool proof.
Fermented mustard.

What to do (brine):

  1. Sanitize container and wash produce. Cut and/or remove stems, seeds, etc. if necessary.
  2. Pack vegetables/fruit into container.
  3. Prepare a 2.5-3.5% brine.
  4. Pour brine over produce until fully submerged.
  5. Cover and put in a dark place.
  6. Move or shake gently to disturb the top of the ferment 2-14 times per week, making sure all fruit/vegetables remain submerged.
  7. Taste after a few days.
  8. Enjoy!

What to do (self brine):

  1. Sanitize container and wash produce. Cut, puree, and/or remove stems, seeds, etc. if necessary.
  2. Weigh produce to be fermented.
  3. Weigh out 3-7% of produce weight in salt.
  4. Pack vegetables/fruit into container, evenly distributing salt as you go.
  5. Press produce to extract juices.
  6. Add regular brine if necessary to submerge all fruits/vegetables.
  7. Cover and put in a dark place.
  8. Move or shake gently to disturb the top of the ferment 2-14 times per week, making sure all fruit/vegetables remain submerged.
  9. Taste after a few days.
  10. Enjoy!
Hot pepper mash ready to ferment. Notice the air bubbles in the jars; I shook and tamped the jars to remove those!

That’s it! Those are the basic guidelines for fermenting fruits and vegetables. Go grab what you need and try it yourself–you’ll be glad you did!

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