Fermentation glossary

Acetic acid bacteria: Bacteria that, given air, turn alcohol into acetic acid: what turns wine or cider into vinegar.; See also: Vinegar mother
Airlock: A lid that lets fermentation gas out without letting air in.; See also: Burping
Amazake: A sweet drink of rice and koji, made with warmth over a few hours. It isn’t acidic, so it goes in the fridge.; See also: Koji
Anaerobic: Without air. That is why vegetables go below the brine: the oxygen mold needs doesn’t reach them there.; See also: Mold, Fermentation weight
Aspergillus oryzae: The koji mold, domesticated in Japan for centuries. Its spores are bought: never grow a mold you can’t identify.; See also: Koji

Botulism: A serious poisoning caused by the toxin of Clostridium botulinum, which grows without air in low-acid foods. It can’t be seen or smelled. Acidity, salt and a tested recipe are what prevent it.; See also: pH, Anaerobic
Brine: Salted water. For pickles it is made separately and poured over the vegetables; in sauerkraut, the vegetables make it themselves as they release their juice.; See also: Dry salting
Burping: Opening the lid of a sealed jar for a moment to let the built-up gas out.; See also: Airlock

Curtido: A Salvadoran ferment of cabbage, carrot, onion and oregano, served with pupusas.; See also: Sauerkraut

Discard: The portion of sourdough starter removed before feeding. It goes into crackers, pancakes and more.; See also: Sourdough starter
Dry salting: The method in which salt is mixed straight into shredded or finely cut vegetables, which release their own juice. Salt is worked out on the weight of the vegetables.; See also: Brine

Fermentation crock: A large ceramic vessel, sometimes with a water channel around the rim that acts as an airlock, for fermenting in quantity.; See also: Airlock
Fermentation weight: A glass or ceramic disc or stone that keeps the vegetables below the brine.; See also: Anaerobic

Ginger bug: A starter of ginger, sugar and water, fed for a few days until it bubbles, used to make fermented sodas.; See also: Starter, Wild fermentation
Gochugaru: Korean chili flakes, red and mildly hot, that give kimchi its color.; See also: Kimchi

Hydration: In bread, the water in a dough over the weight of the flour, as a percentage.; See also: Sourdough starter
Hydrometer: A glass float that measures the gravity of a liquid.; See also: Specific gravity, Refractometer

Jun: A drink similar to kombucha made with green tea and honey instead of black tea and sugar.; See also: Kombucha

Kahm yeast: A yeast that forms a flat white, gray or pinkish film on the surface of a ferment. It isn’t mold, but it should be skimmed off: it spoils the flavor and, if it grows a lot, lowers the acidity.; See also: Mold
Kefir grains: Soft, cauliflower-like clusters of bacteria and yeasts that ferment milk. They grow, get strained out and are used again.; See also: Water kefir
Kimchi: The Korean ferment of napa cabbage, radish and a paste of garlic, ginger and chili. It ferments fast and keeps maturing in the fridge.; See also: Gochugaru
Koji: Rice or barley covered in a domesticated mold, Aspergillus oryzae. It is how miso, soy sauce, sake and amazake are made.; See also: Aspergillus oryzae, Miso, Amazake, Shio koji
Kombucha: Sweetened tea fermented with a SCOBY. First it sours in an open jar; then, for fizz, it is bottled.; See also: SCOBY, Second fermentation
Kvass: An Eastern European drink. Bread kvass is made with rye bread and is very low in alcohol; beet kvass, with beets and salt.

Lactic acid bacteria: The bacteria behind most vegetable and dairy ferments. They turn sugars into lactic acid, which sours the ferment and protects it.; See also: Lacto-fermentation, pH
Lacto-fermentation: Fermentation carried out by lactic acid bacteria. It is what makes sauerkraut, kimchi, brine pickles, yogurt and kefir.; See also: Lactic acid bacteria

Mead: Honey, water and yeast. It ferments in weeks and matures over months.; See also: Specific gravity
Miso: A paste of soybeans, salt and koji that matures for months or years. The longer and saltier, the darker and stronger.; See also: Koji
Mold: A fungus that needs air and grows raised: fuzz, dots or velvety circles, usually green, blue, brown or black. If it appears on a vegetable ferment, the whole batch goes.; See also: Kahm yeast, Anaerobic

Nukazuke: Japanese pickles made in a bed of fermented rice bran, the nukadoko, stirred every day or every few days.

Pasteurize: To heat a food just enough to kill dangerous microbes without fully cooking it. Milk and juice fermented at home should be pasteurized.
pH: The measure of how acidic something is: the lower, the more acidic. In a vegetable ferment, a falling pH is the sign that fermentation has gone well.; See also: pH meter
pH meter: A device that measures pH with a probe. It is more precise than strips and needs calibrating now and then.; See also: pH

Refractometer: A device that measures the sugar in a few drops of liquid by how they bend light.; See also: Hydrometer
Rhizopus: The white mold that binds tempeh’s legumes together.; See also: Tempeh

Sauerkraut: Shredded cabbage fermented with salt in its own juice.; See also: Dry salting
SCOBY: The rubbery disc that grows on kombucha: a colony of bacteria and yeasts. It passes from one batch to the next with its starter liquid.; See also: Starter, Kombucha
Second fermentation: The stage in a sealed bottle, with a little fruit or sugar, that makes kombucha or water kefir fizzy. It needs the most care, because pressure builds.; See also: Kombucha, Water kefir
Shio koji: Koji with salt and water, fermented for a week. Used as a seasoning and a marinade.; See also: Koji
Sourdough starter: Flour and water where wild yeasts and lactic acid bacteria live. It is fed regularly and raises bread.; See also: Discard, Hydration
Specific gravity: In mead, cider and wine, how heavy the liquid is compared with water. More sugar means higher gravity; it falls as it ferments. The gravity at the start and the end gives the alcohol.; See also: Hydrometer
Starter: Part of an earlier ferment added to a new one so it starts acidic and with the right microbes, such as the liquid of a finished kombucha.; See also: SCOBY

Tempeh: Soybeans or other legumes bound into a firm cake by Rhizopus mold, incubated for a day or two somewhere warm. It is cooked before eating.; See also: Rhizopus
Tepache: A Mexican drink of pineapple peel, piloncillo and spices, fermented for a few days by the fruit’s own yeasts.; See also: Wild fermentation

Vinegar mother: The jelly-like layer of acetic acid bacteria that forms on live vinegar and can start another batch.; See also: Acetic acid bacteria

Water kefir: Sugar water fermented with its own translucent grains, called tibicos in Mexico.; See also: Kefir grains, Second fermentation
Wild fermentation: Fermentation that starts on its own with the microbes the ingredients or the air already carry, with no culture added.; See also: Starter

Yeast: A single-celled fungus that turns sugar into alcohol and gas. It raises bread and gives kombucha, water kefir, cider and mead their bubbles and alcohol.; See also: Kahm yeast, Wild fermentation

Glossary