How does fermenting food work to preserve it?

Question answered by Miles Knowles

MBA Sustainability from Bard College and studied resilience in food systems.

The historical purpose of fermentation was preserving fresh food in a time before refrigeration, although the health benefits of lactic acid fermentation have sparked a new generation of home fermentation enthusiasts. Lactic acid fermentation, or lacto-fermentation, is an anaerobic (oxygen-free) process where lactic acid bacteria convert sugar into lactic acid, providing an environment where food is preserved without refrigeration. While traditional canning allows for longer storage times, lacto-fermentation provides greater health benefits by allowing friendly bacteria, or probiotics to grow.

Lacto-fermentation utilizes salt and water to create an anaerobic environment where only the lactobacillus bacteria can survive. Lactobacillus is a type of probiotic, a friendly bacteria that aids digestion, boosts immunity, reduces inflammation, and provides a myriad of other health benefits. Lactobacillus is commonly found in foods such as yogurt, miso, cheese, and sauerkraut. Some store-bought probiotic capsules may contain billions of lactobacilli, but a few spoonfuls of homemade sauerkraut may contain trillions.

Adding salt to a vegetable and submerging it under water allows the lactobacilli bacteria and yeast naturally found on vegetables to grow and multiply. Rubbing salt into a water-rich vegetable like cabbage causes the cabbage to release its water content, which can then be used as a brining solution. A fermentation brine may also be prepared by dissolving salt in non-chlorinated water and submerging the vegetables to be fermented. It is important to ensure that vegetables remain under water during the fermentation process in order to discourage mold growth and ensure even distribution of the salt. Using salt in a ferment also hardens a vegetable’s pectins, helping to maintain crispness, even when preserved for many months.

Sauerkraut / Kvass / Kimchi

Temperature impacts the rate of fermentation, with warmer temperatures (68-80F) providing a more rapid fermentation and cooler temperatures (35-50F) being an ideal “parking place,” for ferments that have achieved their desired flavor/consistency. Lacto-fermentation, when properly prepared, is considered safer than traditional canning, as bacteria like botulism cannot survive in the salty, acidic environments required for lactobacilli to grow. When preparing a lacto-ferment, it is important to follow suggested salt and water ratios and maintain cleanliness throughout the process. Although mold may sometimes occur on lacto-ferments when food is not entirely submerged under brine, this mold may be scooped out and discarded, leaving the fermented vegetables underneath palatable and safe to eat.

Tasting is believing

  1. Finely shred a head of clean cabbage

2. Mix the shredded cabbage with 2% of its weight worth of non-iodized salt.

3. Pack firmly into a sealable container. Let sit for at least 3 weeks. Release pressure occasionally.

No additional water is needed. Seasonings such as caraway can be added at the start. The salt creates a pH that inhibits the growth of botulism.

Thanks to Haley Slone of Full Circle Education in Driggs for the pictures and the workshop about fermentation. To learn more about fun and practical workshops in the future go to :

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