Fermentation
Fermentation is a biological process where microorganisms, such as yeasts, bacteria, and molds, convert carbohydrates like starch and sugars into simpler substances, including alcohols, acids, and gases. This process is typically anaerobic, meaning it doesn't rely on oxygen, although some types can occur in its presence. Fermentation has been utilized by humans for thousands of years, dating back to at least 7000 BCE in China, where it was used to create fermented beverages. Over the centuries, fermented foods and drinks have played significant social, religious, and dietary roles across various cultures, from the brewing of beer in medieval Europe to the production of miso and sake in East Asia.
The scientific understanding of fermentation advanced significantly in the 19th century, particularly through the work of figures like Louis Pasteur and Eduard Buchner, who elucidated the biological mechanisms involved. Today, fermentation is recognized not only for its culinary applications, such as in bread, cheese, and yogurt production, but also for its health benefits, including the presence of probiotics and enhanced digestibility of fermented foods. Moreover, fermentation has implications beyond food, playing a crucial role in pharmaceuticals, biofuel production, and environmental applications like wastewater treatment. This multifaceted process continues to be of great importance in both traditional practices and modern scientific advancements.
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Subject Terms
Fermentation
Fermentation is a biological process in which a microorganism converts carbohydrates, typically starch or sugar, into simpler components such as alcohols, acids, and gases. More broadly, the term “fermentation” is also used to refer to any transformation of organic matter by enzymes. The most common groups of microorganisms involved in the fermentation of food include yeasts, bacteria, and mold, which produce enzymes that catalyze the fermentation process.
In common usage, “fermentation” usually refers to an anaerobic process, meaning it does not require oxygen, though oxygen may be present in certain types of fermentation processes. Humans have been taking advantage of the products of fermentation for culinary purposes since the Neolithic Period, although the science behind this phenomenon was not explored in earnest until the mid-nineteenth century. The advances that this exploration set in motion enabled the practical applications of fermentation to expand into other fields, such as pharmaceuticals, biotechnology, and nutrition.
Background
Fermentation has been used for culinary applications since at least several thousand years BCE. The earliest known example comes from China circa 7000 BCE, with scientists discovering evidence in pottery remnants of a beverage made from fermented rice, honey, and fruit. Fermented beverages have since become vital in societies across historical and geographical boundaries. Due to their once-mysterious combination of anesthetic, antiseptic, and intoxicating properties, alcoholic beverages in particular have played important social roles, both secular and religious, throughout the history of civilization.
Overview
Around the same time that fermentation was beginning to be used in China, alcoholic beverages were also being fermented in the Middle East. Both beer and wine were important offerings to the gods in ancient Egypt. Later, in ancient Greece and Rome, wine was the fermented beverage of choice. Indigenous South Americans produced a wide variety of fermented beverages using ingredients that were readily available to them, such as corn and cassava. As with the Egyptians, these beverages often played important roles in religious ritual. In medieval Europe, beer and wine were of particular importance, serving as sanitized versions of drinking water to prevent the rampant spread of waterborne infectious diseases.
Throughout the Middle Ages and beyond, fermented beverages continued to play important social, medical, and religious roles. Across Europe, the brewing of beer became a crucial part of supporting monasteries run by Trappists, a religious order of the Roman Catholic Church. Trappist monks brewed for their own consumption, the consumption of the community, and eventually as a primary means of funding their works through the sale of beer. On a social level, community was often centered on tavern life and the consumption of beer. This tradition was brought to North America by European settlers in the seventeenth and eighteenth centuries.
The culinary applications of fermentation have by no means been limited to beverages. Since prehistoric times, fermented foods have been a dietary staple for most of the human race. Most commonly, many kinds of bread and cheese are produced using fermentation. Bread is leavened using yeast fermentation, while many cheeses are produced through mold fermentation by adding an enzyme complex called rennet.
In the West, fermentation, with the exception of cheeses, has always been more closely associated with yeast. Historically, East Asian cuisine has made a very different, more extensive use of fermented food. A crucial component of the East Asian diet since at least 300 BCE has been Aspergillus oryzae, also known as koji, a fungus used to ferment grains and soybeans. Koji has been used in East Asian cultures for thousands of years to produce such foods and beverages as miso, sake, and amazake.
In the nineteenth century, several advances were made in understanding the science behind fermentation, called zymology or zymurgy. The most important of these was made by French microbiologist and chemist Louis Pasteur (1822–95) in the 1850s and 1860s. While studying fermentation processes, Pasteur proved that the fermentation is brought on by living organisms rather than by spontaneous generation, as was previously believed. Further investigation showed that specific microorganisms cause specific types of fermentation. This knowledge allowed for increased control over the fermentation process.
The second major advancement in the technology of fermentation was the result of experiments by German chemist Eduard Buchner (1860–1917), who discovered that living yeast cells do not need to be present for fermentation to occur, as the enzymes produced by the yeast cells are the agents responsible for fermentation. Buchner also discovered that fermentation can take place in the presence of oxygen. For his contributions to the science of fermentation, Buchner received the 1907 Nobel Prize in Chemistry.
In addition to bread and cheese, many other foods are produced using fermentation. The processes used to make chocolate, yogurt, bread, sauerkraut, soy sauce, kimchi, sour cream, tempeh, poi, kombucha, traditional pickles, and vinegar all involve fermentation in some capacity. Coffee is sometimes produced via a process called the “ferment and wash” method, in which the pulp of coffee cherries is removed from the bean by breaking down the cellulose through fermentation, but this process was predated by forms of dry processing and has been steadily replaced by machine-assisted wet-processing methods.
The twenty-first century has seen an increased recognition of the nutritional value of fermentation. Proponents of incorporating fermented foods into one’s diet cite numerous health benefits, including the increased vitamin levels and improved digestibility of fermented foods. The fermentation process creates probiotics that make foods more easily digestible and enriches them with vitamins and enzymes. In addition, fermentation changes the texture and flavors of some foods, making them more palatable to human tastes. It also acts as a natural preservative and provides far more health benefits than chemical preservatives.
Increased knowledge of the nature of fermentation has also had a profound effect on the modern beer industry. The resurgence of the craft-beer industry in the twenty-first century would not have been possible without the work of scientists such as Pasteur. Expanded knowledge of the effect that different agents of fermentation, such as yeast and bacteria, have on the properties of the finished product is a key tool used by craft brewers in particular.
Studies in zymology have led to significant developments in nonculinary fields as well. In the pharmaceutical and medical fields, fermentation is used in the synthesis of antibiotics, vitamins, and other drugs. A variety of useful products can be created by way of industrial fermentation. Because one of the by-products of fermentation is alcohol, often butanol and ethanol, the process can be used to produce biofuel. Acetone, used as a cleaning solvent, is another by-product of certain types of fermentation. Fermentation is also used to treat wastewater, a process that has the added benefit of producing usable biofuel in addition to breaking down the waste product.
Bibliography
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