Living Cultures: Thirteen Fermentations Behind Staple Foods

Backslopping uses a small quantity of a previously fermented batch as the starter for the next one. It shortens fermentation time and is still used today for idli, kefir, kombucha and sourdough.

Injera batter is started with ersho, a clear yellow liquid that collects on the batter and carries the fermenting microbes. A cooked portion called absit is then mixed back in for a shorter second fermentation.

Idli batter is four parts rice to one part black gram, fermented overnight until it more than doubles in volume. Lactic acid bacteria, delivered mainly by the black gram, leaven the batter and raise its acidity.

Ogi starts with maize, sorghum or millet soaked for up to three days, then milled and sieved. Lactic acid bacteria and wild yeasts do the souring, and the result is cooked into a thin pap or a firmer pudding.

Kenkey maize is steeped for about a week, kneaded into dough and left to ferment for four days to a week before steaming. This long fermentation separates it from simpler maize preparations such as ugali and gives it a sour flavor.

Kocho turns the pulp of the enset plant into a bread-like food, started with older fermented pulp. Fermentation can run from several weeks to two years, and stored kocho gives households a reserve through scarcity.

Attieke is grated cassava fermented for one or two days with a little earlier fermented cassava as starter. This step removes most of the hydrocyanic acid in bitter cassava, and steaming then finishes the granules.

Garri is made by pressing cassava mash for one to twenty four hours and then frying the sieved granules. The final heating dries the granules and finishes destroying the toxic compounds naturally present in cassava.

Koji grows the mold Aspergillus oryzae on steamed grain or soybeans for two to three days at about 30 degrees Celsius. Yellow koji goes into soy sauce and miso, black koji into awamori and white koji into shochu.

Southeast Asian shrimp paste starts with small shrimp rinsed, dried and mixed with salt, which darkens and breaks down into pulp over several days. The fully fermented paste needs no refrigeration and is sold as dried bricks.

Prahok, from Cambodia, is made from freshwater fish that are descaled, pressed, salted and pounded. It ferments for about a month and is considered mature once no more liquid appears.

Cocoa beans are fermented by yeasts, lactic acid bacteria and acetic acid bacteria acting on the pulp around them. This develops the flavor precursors that become chocolate flavor during roasting and reduces bitterness.

Fresh olives are bitter because of oleuropein, which can make up as much as fourteen percent of a young olive's dry matter. Curing takes a few days with lye or several months with brine or dry salt.