SCOBY
Also known as: symbiotic culture of bacteria and yeast, symbiotic colony of bacteria and yeast, kombucha culture
A SCOBY (symbiotic culture of bacteria and yeast) is a living starter in which yeasts, acetic acid bacteria and often lactic acid bacteria work together to ferment a sweetened liquid. The best-known example is the rubbery cellulose mat, or pellicle, that floats on kombucha. The term also covers the microbes suspended in the liquid itself. Related cultures include the grains used for milk kefir and water kefir, and the mother of vinegar.
Usage in beverages
A piece of SCOBY is added to cooled, sweetened tea along with some liquid from a previous batch, a step known as backslopping. The vessel is covered with breathable cloth and left at room temperature for one to two weeks. Yeasts turn sugar into alcohol and carbon dioxide, and acetic acid bacteria then oxidize most of that alcohol into acids. The result is a tart, lightly sparkling, usually very low-alcohol drink that is often flavored with fruit or spices in a second, bottled fermentation. Related cultures ferment milk into kefir, sugar water or fruit into water kefir and tepache de tibicos, and wine or cider into vinegar.
In depth
Uncertain beginnings in northern China
The kombucha culture most likely emerged in northern China, with the coastal Bohai Sea region often suggested as its home. However, no reliable written record fixes a date or place. Before the twentieth century the fermented tea seems to have been a local remedy rather than a national drink. Some traditional practitioners gave it for lung and stomach complaints. Chinese names for the culture reflect how it was seen: 'sea treasure' compared the floating, jelly-like mat to a jellyfish, and 'stomach treasure' pointed to its supposed digestive benefits. Romantic stories placing it at the court of the first Qin emperor, or crediting a Korean physician who served it to a Japanese emperor, have no supporting evidence. They are best understood as later marketing legends.[1]
Caucasus kefir grains: a dairy cousin
In the North Caucasus a different symbiotic culture developed around milk. Small, cauliflower-like kefir grains hold lactic acid bacteria, yeasts and sometimes acetic acid bacteria in a polysaccharide matrix. When added to cow, goat or sheep milk, they produce a sour, faintly fizzy and slightly alcoholic drink. Herders traditionally fermented it in goatskin bags hung by a doorway, and passers-by jostled the bags to keep grains and milk mixed. Like a kombucha mat, the grains grow and divide with each batch, so they could be shared and handed down. Kefir spread through Russia in the late nineteenth century and later across Europe, North America and Japan. It is still a daily drink across Eastern Europe and West Asia.[2]
Mothers of vinegar and the European sour-drink tradition
European winemakers and cider makers knew a close relative of the kombucha mat long before kombucha arrived. This was the mother of vinegar, a cellulose veil of acetic acid bacteria that forms on alcoholic liquids left open to air. Eighteenth- and nineteenth-century scientists described it variously as a 'flower', a fungus and finally a bacterial culture. The Orleans method in France floated mothers on wine in shallow vats to make vinegar at scale. The vinegar mother is the source of the acetic tradition behind drinking vinegars such as shrubs, switchel and oxymel. It differs from a kombucha culture mainly in tolerating much higher acidity, and it cannot simply be swapped in to brew tea.[3]
Ginger beer plants and Mexican tibicos
Sugar-fed grain cultures spread through the nineteenth century under a long list of folk names, including ginger beer plant, beer seeds, California bees and tibicos. Translucent grains dropped into sweetened water, sometimes with ginger, dried fruit or citrus, ferment within a day or two into a tangy, naturally carbonated drink. American accounts describe such grains being used in Kentucky around 1859 for a homemade 'home drink'. British microbiologists studied the ginger beer plant in the 1890s and confirmed it was a symbiotic mix of yeasts and bacteria. Its true origin remains unknown. In Mexico, tibicos are linked in older literature to cactus plants and are used to make tepache de tibicos, a fermented fruit drink. Today the same culture is widely brewed as water kefir.[4]
Russia, Germany and the 'tea mushroom'
By the early twentieth century the kombucha culture had traveled from China into Russia and then into other parts of Eastern and Central Europe, including Germany. There it became a household fixture known as the tea mushroom or Manchurian mushroom. Families kept the mat in a jar of sweet black tea on the kitchen shelf, drew off the tart drink and passed new layers on to neighbors. The word 'kombucha' first appears in English in a 1928 chemical abstract. The name is thought to be a confused borrowing from a Japanese term for an unrelated kelp tea.[1]
East Asian revivals in the twentieth century
The culture reached Japan from Russia. Under the name kōcha kinoko ('black tea mushroom') it became a health fad in the mid-1970s after a popular book promoted it. Home brewers in Taiwan had briefly made it in the 1960s. The Japanese craze then fed back into China, where the drink had long been only a regional curiosity. It enjoyed a national boom in the 1980s under the borrowed name 'red tea fungus'. That wave faded amid safety concerns, reports of contaminated home cultures and limited industrial capacity. Despite these revivals, kombucha remains better known in the West than in China, though drinking it is increasing again across East Asia.[1]
The modern SCOBY: bottled kombucha, craft brewing and home culture
Commercially bottled kombucha appeared in the United States in the late 1990s and grew into a global category in the early twenty-first century. It is now sold widely as a low-alcohol alternative to beer in bars and restaurants. Producers must manage the culture closely, because extended fermentation can push alcohol above the roughly 0.5 percent threshold that separates soft drinks from regulated alcohol. Some makers now deliberately brew 'hard kombucha' at beer strength. Home brewers maintain the same old practices: they add a pellicle together with acidic starter liquid to protect the new batch, split off 'baby' layers, and flavor the finished tea in a second bottle fermentation. Related cultures sit alongside kombucha in the modern fermented-drinks repertoire. These include jun, a honey-and-green-tea relative, as well as water kefir and kefir. Dried, shelf-stable starters are also available as an alternative to fresh mats.[5]