Kombucha

Kombucha is a fermented, effervescent, and sweetened black tea beverage.

It is often referred to as kombucha tea to distinguish the drink from the living culture used to create it. The drink is produced through a process called symbiotic fermentation. This process uses a symbiotic culture of bacteria and yeast, known as a SCOBY.

While many people call the SCOBY a "tea fungus" or "mushroom," it is actually a zoogleal mat. This mat is a living growth of acetic acid bacteria and osmophilic yeast species. People enjoy the drink for its unique bubbles and various flavors. Many brewers add fruit, spices, or juice to customize the taste.

The mechanism of fermentation relies on a complex relationship between different microbes. The SCOBY contains a broad spectrum of yeast species, such as Saccharomyces cerevisiae. These yeasts consume the sucrose in the sweetened tea. They convert the sucrose into fructose and glucose, which are then turned into ethanol.

The bacterial component almost always includes Komagataeibacter xylinus, also known as Gluconacetobacter xylinus. These acetic acid bacteria are aerobic, meaning they require oxygen to grow. They migrate to the air interface at the top of the liquid. There, they oxidize the yeast-produced alcohols into acetic acid and other organic acids. This process increases the acidity of the drink and limits the ethanol content. The bacteria also produce bacterial cellulose, which creates the physical structure of the "mother" mat.

Brewing kombucha involves several distinct stages of production. The process begins by dissolving sugar in non-chlorinated boiling water. Tea leaves are steeped in this sugar water and then discarded. Once the sweetened tea cools, the SCOBY and a small amount of previously fermented tea are added. This technique is called "backslopping," and it helps lower the pH of the mixture.

The container is covered with a breathable fabric to prevent contamination by insects like fruit flies. The mixture ferments at room temperature for 10 to 14 days. During this time, a new "daughter" SCOBY forms on the surface. After fermentation, the liquid is strained and bottled. Some brewers perform a secondary fermentation in the bottle to increase carbonation.

The history of kombucha is filled with both tradition and myth. The drink likely originated in the Bohai Sea region of China. Historically, some Chinese medicine practitioners used it for lung and stomach ailments. It later spread to Russia and parts of Eastern Europe and Germany. In Japan, the drink became a health fad following a 1974 bestseller by Sumako Nakamitsu. However, many popular stories about its history are unproven. There is no evidence that it was served to Emperor Qin Shi Huang in the Qin dynasty. Similarly, claims that a Korean doctor named Kombu served it to Emperor Ingyo are considered apocryphal. These stories were likely invented in the West to increase sales.

Kombucha has become a massive global industry with significant economic value. The global kombucha market was worth billions of dollars and is expected to grow by 2030. In the United States, the market saw rapid growth in the early 21st century. In 2014, U.S. sales of bottled kombucha reached $400 million.

This commercial success led to major business moves, such as PepsiCo purchasing Keiva for approximately $200 million in 2016. Most commercial kombucha in the U.S. contains less than 0.5% alcohol. Because of this low level, it is not federally regulated like beer. However, some producers sell "hard kombucha," which contains over 5% alcohol.

While many people drink kombucha for health reasons, the science is complex. The drink contains B vitamins, such as thiamin, riboflavin, niacin, and vitamin B6. It also contains organic acids like gluconic and acetic acid. Many people believe the live bacteria are probiotics that offer wellness benefits. However, there is very little clinical evidence to support these specific health claims.

Some researchers note a disparity between wide-ranging health claims and actual proven benefits. Because of this, kombucha is not recommended for therapeutic medical use. It is important to note that improper home preparation can lead to contamination. While rare, serious adverse effects have been associated with poorly prepared batches.

Kombucha connects to various fields including microbiology, chemistry, and global economics. From a chemical perspective, the drink is 95% water and 4% carbohydrates. It is a study in how different species, like yeast and bacteria, can live in a mutualistic relationship. The way the bacteria use oxygen to build a cellulose mat is a fascinating biological process. Economically, the drink shows how a traditional beverage can transform into a global commodity. It also highlights how language can shift, as the English name likely arose from a misapplied Japanese term. This term was originally used for a different drink made from kelp.