Lacto-fermentation is the process that produces traditional dill pickles, kimchi, and real sauerkraut, among other fermented delights. This simple fermentation process requires nothing more than salt, vegetables, and water—no canning, no fancy equipment.
The lacto-fermentation process works because of the lucky fact that bacteria that could be harmful to us can't tolerate much salt, while healthy bacteria (think yogurt) can. Think of them as the bad guys vs. the good guys. Lacto-fermentation wipes out the bad guys in its first stage, then lets the good guys get to work during stage two.
The good guys on the salt-tolerant team are called Lactobacillus. Several different species within this genus are used to produce fermented foods. Lactobacillus bacteria convert sugars naturally present in fruit or vegetables into lactic acid. Lactic acid is a natural preservative that helps fight bad bacteria and preserves not only the flavor and texture of food but also its nutrients.
Some strains of Lactobacillus bacteria support digestion and immunity and may help protect against inflammation and chronic disease, including some types of cancer. Different strains of bacteria within the same genus, or family, have strain-specific health benefits.
Traditional lacto-fermentation involves submerging vegetables in a brine solution— salt and water. There are also methods of fermenting without added salt. The salt-brine method involves two stages:
In stage one of lacto-fermentation, vegetables are submerged in a brine that is salty enough to kill off harmful bacteria. The Lactobacillus good guys survive this stage and begin stage two.
In stage two of lacto-fermentation, the Lactobacillus organisms begin converting lactose and other sugars present in the food into lactic acid. This creates an acidic environment that safely preserves the vegetables - and gives lacto-fermented foods their distinctive tangy flavor.
Fermented, Not Canned
While lacto-fermentation is a common and traditional form of pickling and preserving vegetables, it is not the same thing as canning and is not used for long-term preservation. Many fermented foods are edible for two months or more, and their flavors develop and become more acidic over time. Typically, you begin eating a fermented food once it has reached the desired level of fermentation and you finish it before the end of its "shelf life," during which time the flavors will mature and change. By contrast, canning involves some form of sterilization and is intended to preserve food in its canned state for long periods, often for 6 months to a year or more.
Popular Fermented Foods
In general, firm vegetables, such as beets and turnips, are best for lacto-fermentation. Softer vegetables, like tomatoes and cucumbers, can be more difficult. Broccoli, brussels sprouts and other "gassy" foods give off a strong odor when fermented, so it's best to mix them with other vegetables in your recipe. Some of the most common foods used for lacto-fermentation include:
- snap peas
- green beans
Dimidi E, Cox S, Rossi M, Whelan K. Fermented foods: definitions and characteristics, impact on the gut microbiota and effects on gastrointestinal health and disease. Nutrients. 2019;11(8):1806. doi:10.3390/nu11081806
Di Cerbo A, Palmieri B, Aponte M, Morales-Medina JC, Iannitti T. Mechanisms and therapeutic effectiveness of lactobacilli. J Clin Pathol. 2016;69(3):187-203.