What is Lacto-Fermentation?

Nearly one hundred years after Scheele’s discovery, French chemist and microbiologist Louis Pasteur revealed that the acid was created by the bacteria lactobacillus and occurred in the souring and fermentation process of plant and animal products. This discovery came about while Pasteur was perfecting his eponymous pasteurization process to prevent food spoilage. Then another French scientist, Edmond Frémy, purposely produced lactic acid with the fermentation of cow’s rennet. He popularized the use of industrial fermentation practices and built the foundation of modern understandings of lacto-fermentation.

Lacto-fermentation occurs when the lactobacillus bacteria present in a fruit, vegetable, liquid, or piece of meat begins to digest the sugar (i.e., fructose, glucose, sucrose, or lactose) present in that organism. As the bacteria eat the sugar, they create lactic acid which is the substance that gives pickles and other fermented foods their sour taste. The low pH of lactic acid creates an environment that is hostile to many of the bacterial strains that make humans sick. This means that as a grape, carrot, sausage, or jar of milk begins to ferment, usually with the help of a salt and water solution, all the bad bacteria that is present in the fermenting solution is killed off as lactic acid levels increase.

Lacto-Ferments Around the Globe Somewhere between 2.5 billion years ago and Scheele’s 1780 discovery—likely 7000 years ago—humans discovered the preservation effects of lactobacillus and lactic acid, even if they didn’t know how or why those effects occurred. With the recent popularization of fermentation techniques, it would be easy to assume that these are new processes, but this type of preservation has sustained humans through hard times and in difficult environments for thousands of years. Cultures from around the globe have used lacto-fermentation to preserve foods through hard winters and long journeys. The health benefits of fermented products have also been known for quite some time, though we have only recently begun to better understand how eating fermented foods can help with gut microbiome health. Arguably, without these foods humans would not have survived as long or migrated as far.

Parts of Eastern Europe and Russia are notoriously difficult places to live and are therefore often credited with ingenuity in food preservation. Sauerkraut is likely the most famous fermented food to come out of the region, as well as sourdough bread. Russians have traditionally fermented old rye bread into a carbonated drink called kvass and soured dairy is fermented into kefir or smetana. Northern Europe is known for its fermented meats, such as pickled herring and lutfisk, and a trip to Iceland may involve a dare to try some hakarl (fermented shark).

Other lacto-ferments from around the world include Ethiopian injera (unleavened sourdough), amasi (soured milk), Korean kimchi, sufu (fermented tofu), Japanese umeboshi (pickled plums) and countless others. Many of these recipes and techniques are the result of humans attempting to preserve food in hot climates, droughts, and for long journeys by desert, mountain, and sea. Today we have the freedom to experiment with ferments aided by pH testers, refrigerators, and abundant food sources. But for millennia, these fermented foods were a matter of life and death.

Basic Formula for Lacto-Fermentation Since you likely have a refrigerator and either a garden or a grocery store nearby, you have everything you need to experiment with and perfect your lacto-fermentation recipes. To get started, here a few basic tips to kick start the pickling process on anything you plan to ferment.

Salt, Temperature, and Time Almost all lacto-fermentation relies on the presence of salt, which aides in the bacteria-killing process and adds flavor. Using a scale is essential in fermentation because variations in salt grain sizes and densities can lead to vastly over- or under-salted brines. Weighing ingredients in grams will give you the most precise measurements and allow you to have more control over the fermentation process. The optimal salt formula for lacto-fermentation is the weight of the vegetables or fruit, plus the weight of the water, all multiplied by .025. This means that the amount of salt in the solution should always be about 2.5%. This is true for both brine ferments as well as meat preservation. Dairy ferments will need a starter culture, such as buttermilk, instead of salt to kick-start fermentation.

Speaking of control, keeping your ferment at room temp—between 60-75°F—will allow microbes to work at a steady rate. Anything colder than 60 will cause the microbes to go dormant and either delay or completely stop fermentation. Anything hotter than 75 will cause over-fermentation which not only ruins your ferment but can create a big mess as the bubbly concoction tries to escape its jar.

Lacto-fermentation needs an anaerobic (oxygen-free) atmosphere to thrive. Oxygen not only halts the fermentation process but the presence of oxygen along with any bad bacteria will allow those dangerous microbes to thrive. To avoid this, make sure that your fermentation vessels, hands, knives, and all other tools are clean and sanitized. When packing your ferment into a jar or crock, pack the ingredients down underneath the liquid solution and push out all the bubbles. Then, if possible, place a weight on top of the ingredients to keep them submerged.

Within a day or two, the liquid in the ferment will turn cloudy and you will begin to see bubbles. These are both good signs of a healthy ferment. While the fermentation never truly stops, you’ll know your ferment is ready when the bubbles start to slow down and it gives of a sour aroma, likely at about 7 to 10 days (you can safely leave it out for up to 21 days if you want a sourer pickle).

To stop fermentation, simply put your jar or crock in the refrigerator. Your fermented foods should last for a few months in refrigerated climates, but you might find yourself polishing off your lactobacillus creations much sooner than that.