Also known as alcohol fermentation.
Using "good" fermenting bacteria (ie. Lactobacillus) and enzymes to convert sugars, starches and carbohydrates found in the food into alcohol and preserving acids (ie acetic acid). This results in a preservable product that is tastier, more nutritional and also easier to digest.
Examples of fermented foods include: beans, beer, bread, brined vegetables, kimchi, kombucha, mead, salami, sauerkraut, sourdough, sprouted grains, vinegar, wine.
Fermentation methods: using a starter culture (which contains the fermenting bacteria) or curing in a brine solution. The starter culture can be purchased or you can often using a little from a previous batch. Curing in a brine solution (salt + water + sometimes sugar and/or spices) results in a naturally fermented or pickle-tasting product without the addition of vinegar like pickling does. The fermentation method you use depends on what food you are fermenting, so refer to a recommended fermenting recipe and follow steps accordingly.
ie. apples: fermenting apples makes apple cider, then you can make apple cider vinegar.
ie. bread: yeast eats the sugar and creates carbon dioxide gas and alcohol. The carbon dioxide gas is what causes the bread to rise (the alcohol is burned off during baking).
ie. wine: fermenting grape juice creates alcohol. This will store for a LONG time without refrigeration, whereas grape juice needs to be canned, frozen or consumed within a few days. Always follow a recommended recipe when fermenting, and label then store safely as the recipe states.
Lactic acid fermentation.
Using "good" fermenting bacteria (ie. Lactobacillus) and enzymes to convert sugars, starches and carbohydrates found in the food into lactic acid.
Examples: fermented dairy products (ie. cheese, yoghurt), kefir, cucumbers, carrots, beets, green beans, pearl onions, radishes, tomatoes.
Food is placed in a brine (water + salt mixture) and set aside to develops lactic acid which preserves the food and prevents bad bacteria growth (which would cause spoilage). You will know if it has gone bad as it will smell bad! An interesting note is that many lactose-intolerant people can consume lacto-fermented products. Always follow a recommended recipe when lacto-fermenting, and label then store safely as the recipe states.