50 Fun Facts About Fermentation

Which popular pet fish can survive long spells without any oxygen by making alcohol in its muscles?

Goldfish and their wild cousins, crucian carp, turn the waste from oxygen-free living into alcohol that drifts out through the gills. Most backboned animals die within minutes without oxygen.

Captain James Cook took sauerkraut on his long sea voyages to protect his crew from which disease?

Scurvy comes from a lack of vitamin C, which raw sauerkraut supplies. Fermenting the cabbage also gave it the long shelf life needed for voyages that lasted years.

Surströmming, a fermented herring notorious for its smell, is a traditional delicacy of which country?

Sweden's sour herring keeps fermenting inside the tin until the can bulges. The smell is so strong that it is usually opened and eaten outdoors.

Iceland's national dish hákarl is made by fermenting and then drying the meat of which animal?

Shark meat from the Greenland species is poisonous when fresh because it is full of urea. Curing and hanging it for months makes it safe, though the ammonia smell makes many first-timers gag.

Which sweet treat gets its flavour from seeds fermented in their own pulp for days before roasting?

Chocolate begins as cacao seeds heaped under mats or banana leaves for three to seven days. The heat of fermentation turns the purplish beans brown and starts building the flavour.

What is the name of the rare condition in which microbes in the gut ferment food into alcohol?

Auto-brewery syndrome can leave people slurring and unsteady without a single drink. It has even been raised in court as a defence against drink-driving charges.

Deep-tank fermentation let drug makers brew enough of which antibiotic to supply Allied troops on D-Day?

Penicillin was once so scarce that it was recovered from patients' urine and reused. Fermentation tanks changed that, and 2.3 million doses were ready for the Normandy landings.

Which hormone, grown in tanks of engineered bacteria, became the first licensed genetically engineered drug?

Insulin from engineered E. coli went on sale as Humulin in 1982. Until then, people with diabetes relied on hormone extracted from the pancreases of cows and pigs.

Chaim Weizmann, whose fermentation process made acetone for explosives, became which country's first president?

Israel's first president was a biochemist whose process kept Britain supplied with cordite propellant in World War I. He is considered the father of industrial fermentation.

Which small fish goes into Worcestershire sauce, the fermented condiment invented by two English pharmacists?

Anchovies appear on a 19th-century Lea & Perrins ingredient list that turned up in a skip at the factory in 2009. The exact recipe is still a trade secret.

Which gas, released by yeast as it ferments sugar in dough, makes a loaf of bread rise?

Carbon dioxide forms bubbles that stretch the dough into a foam. The yeast makes alcohol too, but less than 2% of it is left after baking.

Which French chemist showed in the 1850s that living microbes, not mere chemistry, cause fermentation?

Louis Pasteur went on to sum up fermentation as life without air. He also traced the yeast that ferments wine to the skins of the grapes themselves.

Which acid, made by bacteria fermenting sugars, gives yogurt and sauerkraut their sour tang?

Lactic acid does double duty: it sets the milk protein that thickens yogurt, and it preserves sauerkraut for months without a fridge.

Which type of alcohol, the one found in beer and wine, does yeast make when it ferments sugar?

Ethanol is really the yeast's waste product, and each glucose molecule yields two molecules of it. The same reaction now fills fuel tanks as well as wine glasses.

Yeast, a one-celled organism behind bread and beer, belongs to which kingdom of living things?

Fungi include yeast alongside moulds and mushrooms. Most yeasts multiply by budding, in which a small daughter cell swells out of its parent.

Fermentation earns a cell just two molecules of which energy carrier per glucose, far fewer than respiration?

ATP is the cell's energy currency. Respiration with oxygen can wring roughly 30 molecules from the same glucose, about fifteen times as many.

Mead, possibly the most ancient alcoholic drink of all, is made by fermenting which ingredient with water?

Honey supplies the sugar in mead, which may have been discovered 20,000 to 40,000 years ago, before farming or pottery existed.

Which Korean staple is made in bulk and left to ferment before each winter, a custom on UNESCO's heritage list?

Kimchi season is called gimjang, a month when households prepare enough to last the whole winter. UNESCO added the custom to its heritage list in 2013.

Which fizzy drink is made by fermenting sweetened tea with a rubbery mat of bacteria and yeast?

Kombucha's floating mat is known as a SCOBY, a mother or a mushroom, though it is really a film of microbes. In Chinese it was once called sea treasure because it looks like a jellyfish.

Which kitchen staple, made by letting bacteria work on alcohol, takes its name from Old French for sour wine?

Vinegar forms in a double fermentation: yeast first turns sugar into alcohol, then bacteria turn that alcohol into acid. A slimy raft of those bacteria is known as the mother.

Which tangy bread is raised by a starter of wild yeast and bacteria rather than packaged baker's yeast?

Sourdough travelled with Klondike gold miners, who carried pouches of starter on their belts and guarded them from the cold. In fact freezing does not kill a starter, but excessive heat does.

Most yeast stop fermenting at about 15% alcohol, so stronger drinks such as whisky need which extra process?

Distillation concentrates the alcohol from a liquid that has already been fermented. Spirits typically leave the still above 50% and are diluted before bottling.

Which fruit is too bitter to eat straight from the tree and is usually cured and fermented first?

Olives owe their raw bitterness to a compound called oleuropein, which curing and fermenting strip out. About 80% of the harvest never reaches the table and is pressed for oil.

Which dark British spread is made from the yeast left over after beer has been brewed?

Marmite got its first factory in 1902 in Burton upon Trent, where the Bass brewery supplied the spent yeast. A German chemist had shown that brewer's yeast could be concentrated, bottled and eaten.

Caribbean rum traditionally begins when yeast ferments which by-product left over from refining cane sugar?

Molasses was a mere leftover until, by the traditional account, enslaved workers on 17th-century Caribbean plantations found that it could be fermented into alcohol.

Perry is an alcoholic drink made much like cider, but by fermenting the juice of which fruit?

Pears grown for perry are small and bitter, much as cider apples differ from the ones sold for eating. The drink is a speciality of England's western counties and of Normandy.

Which country fuels much of its car fleet with alcohol fermented from its vast sugarcane crop?

Brazil no longer has any light vehicles running on pure petrol: every litre sold is blended with cane alcohol, and flex-fuel cars can run on any mix of the two.

Cattle belch which greenhouse gas, made as microbes ferment grass inside their stomachs?

Methane from cattle, sheep and their relatives makes up around a third of the methane released by human activity. About 95% of it leaves as burps, not from the other end.

What do bakers call the final rest in which yeast ferments shaped dough and puffs it up before baking?

Proofing is called proving in Britain and Australia. Bakers use the same word for soaking dried yeast in warm water to wake it up before mixing.

Kumis, a mildly alcoholic drink of the Central Asian steppe, is made by fermenting the milk of which animal?

Horse milk carries more sugar than the milk of cows or goats, which is why kumis ferments into something mildly alcoholic as well as sour.

Which ten-step pathway breaks glucose in half and supplies the raw material for fermentation?

Glycolysis needs no oxygen and turns up in nearly every living thing, a sign that it is one of the most ancient pathways in biology.

Which type of human cell has no mitochondria and so depends on fermentation alone for its energy?

Red blood cells discard their mitochondria as they mature, so they burn none of the oxygen they carry around the body.

Which chamber of a cow's stomach serves as the main fermentation vat where microbes break down tough grass?

The rumen is the largest of the stomach compartments, and its microbes digest fibre that a mammal's own gut cannot break down. It is also known as the paunch.

Which Indonesian food is a firm cake of soybeans bound together by a white fermenting mould?

Tempeh comes from Java, where its mould grows wild on the downy undersides of hibiscus leaves that people have long used as food wrappers.

Which Japanese breakfast food is made of whole soybeans fermented by bacteria until sticky and pungent?

Natto relied on straw to carry its bacteria until researchers of the Taisho period, 1912 to 1926, learned to make a starter culture. Its smell and slimy strings make it an acquired taste.

Which Japanese name is given to the mould that starts the fermentation of sake, miso and soy sauce?

Koji mould breaks the starch in rice into sugars, the step that lets a grain with no sweetness of its own be brewed into sake.

Which sour, lightly fizzy milk drink from the North Caucasus is fermented with clumps known as grains?

Kefir was traditionally made in goatskin bags hung near a doorway, and everyone passing through gave the bag a knock to keep the milk and grains mixed.

Which pungent sauce, made by fermenting salted fish in the sun, was a staple seasoning of ancient Rome?

Garum was made from fish intestines and salt, Pliny wrote, yet the best grades fetched extraordinarily high prices.

Injera, a spongy sour flatbread made from fermented teff batter, is the staple food of which African country?

Ethiopia's injera may have begun as an accident, when someone left wet flour standing for a few days and found it made a pleasant bread. A fresh one keeps for only about three days.

Lambic beers, fermented by wild yeast and bacteria instead of a brewer's own cultures, come from which country?

Belgium's lambic brewers rely on microbes native to the Zenne valley near Brussels, and have been making beer this way since the 13th century.

Which molecule, made by splitting glucose, sits at the fork between fermentation and oxygen-based respiration?

Pyruvate enters the Krebs cycle when oxygen is on hand. When it is not, animals and yeast ferment it into two quite different end products.

Which toxic compound, a contributor to hangovers, is the final intermediate yeast makes on the way to alcohol?

Acetaldehyde also forms when the liver starts to break alcohol down, which is how it ends up contributing to hangovers. Yeast runs the same step in the opposite direction.

Which German chemist won a 1907 Nobel Prize for showing that yeast juice with no living cells still ferments sugar?

Eduard Buchner ground up yeast, pressed out the juice and found that the dead liquid still fermented a sugar solution. The result is often called the birth of biochemistry.

After sugar is split for energy, the final steps of fermentation exist to regenerate which electron carrier?

NAD+ collects electrons while sugar is being split. Fermentation hands those electrons on to the leftovers of the sugar, which frees the carrier for another round.

What is the name of the applied science that studies fermentation and its uses in brewing and baking?

Zymology is also called zymurgy. Both names go back to the Greek word for leaven, and so does the word enzyme.

Which South American bird ferments leaves in the front of its gut, much as a cow does, and smells of manure?

The Hoatzin is the smallest known animal to ferment its food cow-style, weighing as little as 700 grams. Locals call it the stinkbird and hunt it only in times of dire need.

Which brewery's laboratory first grew lager yeast from a single pure cell, the work of Emil Christian Hansen?

Carlsberg lent its name to the result, Saccharomyces carlsbergensis, which Hansen isolated at the brewery's Copenhagen laboratory in 1883.

Lager, a beer made with cold-working, bottom-fermenting yeast, takes its name from a German word meaning what?

Storage is the point of the name: Lagerbier was brewed for keeping some months before it was drunk, traditionally in the same cool caves where it had fermented.

Which sour additive in soft drinks is made industrially by feeding sugar to the mould Aspergillus niger?

Citric acid was first crystallised from lemon juice in 1784. Pfizer switched to mould in 1919, two years after a food chemist found strains that produce it efficiently.

West African cooks soak and ferment grated cassava before roasting it into gari, a process that removes which poison?

Cyanide levels in cassava can fall by up to half after 18 to 24 hours of soaking, and pressing and roasting lower them further. Skipping the steps risks konzo, a disorder that affects walking.