We preserve food whenever possible. Preserving food by lacto-fermentation keeps vitamins intact, and in some vegetables, increases its nutritional value. Fermentation also improves the immune system, and digestibility of the food, making them easier for our systems to assimilate.
You don’t need to be an expert to preserve food, or any fancy technology. Just a container, some salt, and trust in the world of bacteria and fungi.
— A. Vansintjan, 2017.
Lacto-fermentation is easy to do, requiring only fresh vegetables, salt, water and air-tight containers. All vegetables can be fermented. Microbial activity occurs which secrete lactic acid, co2 and a variety of enzymes. Lactic acid inhibits the growth of bad bacteria. The mixture eventually achieves a state of balance, and fermentation stops. Conserving vegetables this way can last many years, even when stored at room temperature.
Lacto-fermentation is very safe, the PH of the mixture is so low (below 5) that no pathogens can survive. If ever a fermentation goes wrong, you'll smell it, and it'll be easy to spot, this makes accidentally eating a bad lacto-fermented product very difficult.
We make sauerkraut, and other pickled vegetables (carrots, beet root, garlic etc). We use the dry-salt method. The dry-salting method requires that vegetables be chopped or shredded, for only with lots of surface area exposed can the salt pull water out of the vegetables.
We recommended 3 tablespoons of salt (we use pickling salt, not iodized) per 5 pounds/2.3 kg of vegetables. Salt essentially slows fermentation and enzyme activity and thereby prolongs preservation potential. Temperature also impacts upon the speed of fermentation (fermentation occur faster in summer than winter). If we preserve vegetables with the goal of eating them much later, we add more salt, if the goal is to eat it as soon as it's ready, we use less.
For more about fermentation, we recommend the book The Art of Fermentation by Sandor Ellix Katz, and the blog Nicrunicuit(french) by Marie-Claire Frédéric. Remember, "fermentation is just controlled decay: your most important ingredient is time".