Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitute 1% of all described fungal species.
Bread is a staple food prepared from a dough of flour and water, usually by baking. Throughout recorded history and around the world, it has been an important part of many cultures' diet. It is one of the oldest human-made foods, having been of significance since the dawn of agriculture, and plays an essential role in both religious rituals and secular culture.
Mead is an alcoholic beverage made by fermenting honey mixed with water, and sometimes with added ingredients such as fruits, spices, grains, or hops. The alcoholic content ranges from about 3.5% ABV to more than 20%. The defining characteristic of mead is that the majority of the beverage's fermentable sugar is derived from honey. It may be still, carbonated, or naturally sparkling; dry, semi-sweet, or sweet.
In biochemistry, fermentation theory refers to the historical study of models of natural fermentation processes, especially alcoholic and lactic acid fermentation. Notable contributors to the theory include Justus Von Liebig and Louis Pasteur, the latter of whom developed a purely microbial basis for the fermentation process based on his experiments. Pasteur's work on fermentation later led to his development of the germ theory of disease, which put the concept of spontaneous generation to rest. Although the fermentation process had been used extensively throughout history prior to the origin of Pasteur's prevailing theories, the underlying biological and chemical processes were not fully understood. In the contemporary, fermentation is used in the production of various alcoholic beverages, foodstuffs, and medications.
Sourdough is a bread made by the fermentation of dough using wild lactobacillaceae and yeast. Lactic acid from fermentation imparts a sour taste and improves keeping qualities.
Baker's yeast is the common name for the strains of yeast commonly used in baking bread and other bakery products, serving as a leavening agent which causes the bread to rise by converting the fermentable sugars present in the dough into carbon dioxide and ethanol. Baker's yeast is of the species Saccharomyces cerevisiae, and is the same species as the kind commonly used in alcoholic fermentation, which is called brewer's yeast. Baker's yeast is also a single-cell microorganism found on and around the human body.
Zymology, also known as zymurgy, is an applied science that studies the biochemical process of fermentation and its practical uses. Common topics include the selection of fermenting yeast and bacteria species and their use in brewing, wine making, fermenting milk, and the making of other fermented foods.
Rugbrød is a very common form of rye bread from Denmark. Rugbrød usually resembles a long brown extruded rectangle, no more than 12 cm high, and 30–35 cm wide, depending on the bread pan in which it is baked. The basic ingredient is rye flour which will produce a plain or "old-fashioned" bread of uniform, somewhat heavy structure, but the most popular versions today contain whole grains and often other seeds such as sunflower seeds, linseeds or pumpkin seeds.
Biga is a type of pre-fermentation used in Italian baking. Many popular Italian breads, including ciabatta, are made using a biga. Using a biga adds complexity to the bread's flavor and is often used in breads that need a light, open texture with holes. Apart from adding to flavor and texture, a biga also helps to preserve bread by making it less perishable.
A ferment is a fermentation starter used in indirect methods of bread making. It may also be called mother dough.
Sour mash is a process used in the distilling industry that uses material from an older batch of mash to start the fermentation of a new batch, analogous to the making of sourdough bread with a starter. The term can also be used as the name of the type of mash used in such a process, and a bourbon made using this process can be referred to as a sour mash bourbon.
Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food production, it may more broadly refer to any process in which the activity of microorganisms brings about a desirable change to a foodstuff or beverage. The science of fermentation is known as zymology.
In food processing, fermentation is the conversion of carbohydrates to alcohol or organic acids using microorganisms—yeasts or bacteria—under anaerobic (oxygen-free) conditions. Fermentation usually implies that the action of microorganisms is desired. The science of fermentation is known as zymology or zymurgy.
Tapai is a traditional fermented preparation of rice or other starchy foods, and is found throughout much of Southeast Asia, especially in Austronesian cultures, and parts of East Asia. It refers to both the alcoholic paste and the alcoholic beverage derived from it. It has a sweet or sour taste and can be eaten as is, as ingredients for traditional recipes, or fermented further to make rice wine. Tapai is traditionally made with white rice or glutinous rice, but can also be made from a variety of carbohydrate sources, including cassava and potatoes. Fermentation is performed by a variety of moulds including Aspergillus oryzae, Rhizopus oryzae, Amylomyces rouxii or Mucor species, and yeasts including Saccharomyces cerevisiae, and Saccharomycopsis fibuliger, Endomycopsis burtonii and others, along with bacteria.
In cooking, proofing is a step in the preparation of yeast bread and other baked goods in which the dough is allowed to rest and rise a final time before baking. During this rest period, yeast ferments the dough and produces gases, thereby leavening the dough.
SCOBY is the commonly used acronym for "symbiotic culture of bacteria and yeast", and is formed after the completion of a unique symbiotic fermentation process of lactic acid bacteria (LAB), acetic acid bacteria (AAB), and yeast to form several sour foods and beverages such as kombucha and kimchi. Beer and wine also undergo fermentation with yeast, but the lactic acid bacteria and acetic acid bacteria components unique to SCOBY are usually viewed as a source of spoilage rather than a desired addition. Both LAB and AAB enter on the surface of barley and malt in beer fermentation and grapes in wine fermentation; LAB lower the pH of the beer while AAB take the ethanol produced from the yeast and oxidize it further into vinegar, resulting in a sour taste and smell. AAB are also responsible for the formation of the cellulose SCOBY.
The sponge and dough method is a two-step bread making process: in the first step a sponge is made and allowed to ferment for a period of time, and in the second step the sponge is added to the final dough's ingredients, creating the total formula. In this usage, synonyms for sponge are yeast starter or yeast pre-ferment. In French baking the sponge and dough method is known as levain-levure. The method is reminiscent of the sourdough or levain methods; however, the sponge is made from all fresh ingredients prior to being used in the final dough.
Cider is an alcoholic beverage made from the fermented juice of apples. Cider is widely available in the United Kingdom and the Republic of Ireland. The UK has the world's highest per capita consumption, as well as the largest cider-producing companies. Ciders from the South West of England are generally stronger. Cider is also popular in many Commonwealth countries, such as India, Canada, Australia, and New Zealand. As well as the UK and its former colonies, cider is popular in Portugal, France, northern Italy, and northern Spain. Central Europe also has its own types of cider with Rhineland-Palatinate and Hesse producing a particularly tart version known as Apfelwein. In the U.S., varieties of fermented cider are often called hard cider to distinguish alcoholic cider from non-alcoholic apple cider or "sweet cider", also made from apples. In Canada, cider cannot contain less than 2.5% or over 13% absolute alcohol by volume.
The role of yeast in winemaking is the most important element that distinguishes wine from fruit juice. In the absence of oxygen, yeast converts the sugars of the fruit into alcohol and carbon dioxide through the process of fermentation. The more sugars in the grapes, the higher the potential alcohol level of the wine if the yeast are allowed to carry out fermentation to dryness. Sometimes winemakers will stop fermentation early in order to leave some residual sugars and sweetness in the wine such as with dessert wines. This can be achieved by dropping fermentation temperatures to the point where the yeast are inactive, sterile filtering the wine to remove the yeast or fortification with brandy or neutral spirits to kill off the yeast cells. If fermentation is unintentionally stopped, such as when the yeasts become exhausted of available nutrients and the wine has not yet reached dryness, this is considered a stuck fermentation.
Microbial food cultures are live bacteria, yeasts or moulds used in food production. Microbial food cultures carry out the fermentation process in foodstuffs. Used by humans since the Neolithic period fermentation helps to preserve perishable foods and to improve their nutritional and organoleptic qualities. As of 1995, fermented food represented between one quarter and one third of food consumed in Central Europe. More than 260 different species of microbial food culture are identified and described for their beneficial use in fermented food products globally, showing the importance of their use.
