I know enough to know that the best guide to all this is Wild Fermentation, by Sandor Ellix Katz, also known as Sandorkraut, the self-proclaimed "fermentation fetishist." But since I haven't read that book (shame on me!), here's the bits and pieces I've thus far been able to glean from various sources.
Scientifically, the process looks like this:
Some kind of carbohydrate turns into some kind of acid or alcohol (or carbon dioxide, I think). With wine and beer and cider, obviously, it's alcohol that's produced. With bread, carbon dioxide. With sauerkraut and yogurt and kimchi, lactic acid. Different bacterial strains and yeast, with different inputs, yield different outputs. Basically.
There a bunch of reasons that people do this, among them preservation (the development of certain acids and alcohols delays the decomposition of food), taste (yum!), and health (many people think that healthy bacteria have probiotic characteristics that promote body functions; Sharon Astyk has written that during her pregnancies, because of morning sickness, fermented foods were the only things she could stomach).
There's a really fascinating list on Wikipedia of fermented foods by region:
- Worldwide: alcohol, wine, vinegar, olives, yogurt, bread, cheese
- East and Southeast Asia: amazake, asinan, atchara, bai-ming, belacan, burong mangga, com ruou, dalok, doenjang, douchi, jeruk, lambanog, kimchi, kombucha, leppet-so, narezushi, miang, miso, nata de coco, nata de pina, natto, naw-mai-dong, oncom, pak-siam-dong, paw-tsaynob, prahok, ruou nep, sake, seokbakji, soju, soy sauce, stinky tofu, szechwan cabbage, tai-tan tsoi, chiraki, tape, tempeh, totkal kimchi, yen tsai, zha cai
- Central Asia: kumis (mare milk), kefir, shubat (camel milk)
- South Asia: achar, appam, dosa, dhokla, dahi (yogurt), idli, kaanji, mixed pickle, u-to-nga, jaand (rice beer), sinki, tongba, panir
- Africa: fermented millet porridge, garri, hibiscus seed, hot pepper sauce, injera, lamoun makbouss, laxoox, mauoloh, msir, mslalla, oilseed, ogi, ogili, ogiri
- Americas: chicha, elderberry wine, kombucha, pickling (pickled vegetables), sauerkraut, lupin seed, oilseed, chocolate, vanilla, tabasco, tibicos
- Middle East: kushuk, lamoun makbouss, mekhalel, torshi, boza
- Europe: rakfisk, sauerkraut, ogórek kiszony, surströmming, mead, elderberry wine, salami, prosciutto, cultured milk products such as quark, kefir, filmjölk, crème fraîche, smetana, skyr.
- Oceania: poi, kaanga pirau (rotten corn), sago
What do you all know about fermentation? Sounds pretty cool, doesn't it?