A muffin is an an American English name for a type of bread that is baked in small portions. Many forms are somewhat like small cakes or c cupcakes upcakes in shape, although they usually are not as sweet as cupcakes and generally lack frosting. Savory varieties, such as cornbreadmuffins, cornbreadmuffins, also exist. They generally fit in the palm of an adult hand, and are intended to be consumed by an individual in a single sitting. Outside the United States of America, muffin can also refer to a disk-shaped muffin, usually called an English Muffin outside of England. As American-style muffins are also sold in Commonwealth countries, the term muffin can refer to either product, with the context usually making clear which is meant. There are many varieties and flavors of muffins made with a specific ingredient such as blueberries, blueberries, chocolate chips, cucumbers, cinnamon,, pumpkin, date date,, nut nut,, lemon lemon,, banana banana,, orange, peach, strawberry, boysenberry, almo cucumbers, raspberry,cinnamon nd,, and carrot nd carrot,, baked into the muffin. Muffins are often eaten for breakfast; alternatively, they may be served for tea for tea or at other meals. History
Chocolate chip muffins baking in an an oven
Recipes for muffins, in their yeast-free "American" form, are common in 19th century American cookbooks.[1][2] Recipes for yeast-based muffins, which were sometimes called "common muffins" or "wheat muffins" in 19th century American cookbooks, can be found in much older cookbooks. cookbooks. A somewhat odd combination of circumstances in the 1970s and 1980s led to significant changes in what had been a rather simple, if not prosaic, food. The decline in home-baking, the the health food food movement, the rise of the specialty food coffee trend all contributed to the creation of a new standard of muffin.[citation needed ] shop, and the the gourmet coffee Preservatives in muffin mixes led to the expectation that muffins did not have to go stale within hours of baking, but the resulting muffins were not a taste improvement over homemade.[citation needed ] On the other hand, the baked muffin, even if from a mix, seemed almost healthy compared to the fat-laden alternatives of doughnuts and Danish pastry. "Healthy" grains and such "natural" things as yogurt yogurt and variousvegetables variousvegetables evolved rapidly. But for muffin recipes using using whole grains "healthy" muffins to have any shelf-life without artificial preservatives, the the sugar and fat content needed to be increased, to the point where the "muffins" are almost indistinguishable from from cupcakes. The rising market for gourmet snacks to accompany gourmet coffees resulted in fancier concoctions in greater bulk than the original, modestly sized corn muffin. The marketing trend toward larger portion sizes also resulted in new muffin pan types for home-baking, not only for increased size. Since the area ratio of muffin top to muffin bottom changed considerably when the traditional small round exploded into a giant mushroom, consumers became more aware of the difference between the soft texture of tops, allowed to rise unfettered, and rougher, tougher bottoms restricted by the pans. There was a brief foray into pans that Seinfeld made made reference to could produce "all-top" muffins, i.e., extremely shallow, large-diameter cups. The TV sitcom sitcom Seinfeld Tops" " episode in which the character Elaine character Elaine Benes Benes co-owns a bakery named "Top o' the Muffin to this in the "The " The Muffin Tops You!" that sold only the muffin tops. Along with the increasing size of muffins is a contrary trend of extremely small muffins. It is now very common to see muffin pans or premade muffins that are only one or two inches in diameter. Types of muffins
English muffin Main article: Muffin (English) The English muffin, which predates the American muffin,[citation needed ] is a type of light bread leavened with yeast. It is us ually The two, toasted toasted and served baked in a flat-sided disc-shaped tin, typically about 8 cm in in diameter . Muffins are usually split in two,
a toasting fork. Muffins can also be with butter . Traditionally muffins were toasted in front of an open fire or stove, using a with eaten cold with a hot drink at c offee shops and diners, or split and filled similar to a sandwich (most famously McMuffin). the the McDonald's chain's McMuffin). In her Boston Cooking-School Cook Book , Fannie Farmer gave recipes for both types of muffins, adding instructions for a rings on version that is nearly identical to today's "English muffin". Here the raised-muffin mixture was cooked in in muffin rings a griddle griddle and flipped to brown both sides, producing a grilled muffin. Farmer indicated this was a useful method when baking in an oven was not p ractical. Corn muffin cornmeal are popular in the United States. Though corn muffins can simply be muffin Muffins made from cornmeal shaped cornbread, shaped cornbread, corn muffins tend to be sweeter. Similar to the pan variety, corn muffins can be eaten with butter or as a side dish with stews or chili. Muffin cups
A blueberry blueberry muffin in a paper muffin cup.
metal,[3] with scallop-pressed edges, giving the muffin a round cup shape. Muffin cups are round sheets of paper , foil or metal, They are used in the baking of muffins to line the bottoms of muffin tins, to facilitate the easy removal of the finished muffin from the tin. The advantage to cooks is easier removal and cleanup, more precise form, and moister muffins; however, using them will prevent a crust. Pie A slice of an an apple pie
A pie is a baked dish which is usually made of a a pastry pastry dough casing that covers or completely contains a filling of or savouryingredients. various sweet or savoury Pies are defined by their crusts. A filled filled pie pie (also single-crust single-crust or or bottom-crust bottom-crust ), ), has pastry lining the baking dish, and the filling is placed on top of the pastry, but left open. A top-crust top-crust pie, pie, which may also be called a a cobbler , has the filling in the bottom of the dish and the filling covered with a pastry or other covering before baking. A two-crust two-crust pie pie has the filling completely enclosed in the pastry shell. shell. Flaky pastry pastry is a typical kind of pastry used for pie crusts, but many things can be and crumbs. crumbs. used, including baking powder biscuits, mashed potatoes, and Pies can be a variety of sizes, ranging from bite-size to ones designed for multiple servings.
History vegetables.The need for nutritious, easy-to-store, easy-to-carry, and long-lasting foods Homemade meat pie Homemade pie with with beef and beef andvegetables sea,, was initially solved by taking live food along with a butcher butcher or or cook. cook. However, this on long journeys, in particular at at sea took up additional space on what were either horse either horse-powered -powered treks or small ships, reducing the time of travel before hunter-foraging. additional food was required. This resulted in early armies armies adopting the style of hunter-foraging
baking of processed cereals including the creation of flour , provided a more reliable source of The introduction of the the baking food. Egyptian Egyptian sailors carried a flat brittle millet bread called dhourra cake, while the Romans Romans had brittle bread bread loaf of millet buccellum.[1] a biscuit biscuit called buccellum. The first pies appeared around 9500 BC, in the Egyptian Neolithic Neolithic period or New or New Stone Age, when the use of stone tools shaped by polishing or grinding became common, the domestication of plants and animals, the establishment of permanent villages, and the practice of crafts such as as pottery and weaving. Early pies were known pottery and ground oats barley. These galettes developed into a as galettes, wrapping honey honey as a treat inside a cover of ground oats,, wheat wheat,, rye rye or barley form of early sweet sweet pastry pastry or desserts the Pharaoh Ramesses II, who or desserts,, evidence of which can be found on the tomb walls of the
ruled from 1304 to 1237 BC, located in the the Valley of the Kings.[2] Sometime before 2000 BC, a recipe for chicken pie was written on a tablet in in Sumer .[3] With the knowledge transferred to the Ancient Greeks, Greeks, historians believe that the Greeks originated pie pastry. Then a flour-water paste (add fat, and it becomes becomes pastry),[4] wrapped around meat, served to: cook the meat; seal in the juices; and provide a lightweight sealed holder for long sea journeys. This transferred the knowledge to the the Romans who, having conquered parts of Northern Europe and southern southern Spain Spain were far more adept at using salt and spices to preserve and flavour their meat. meat.[2] The 1st century Roman cookbook Apicius cookbook Apicius make various mention of various recipes which involve a pie case. case .[5]By 160 BC, Roman statesman statesman Marcus Porcius Cato (234-149 BC) who wrote wrote De Agri Cultura Agri Cultura, notes the recipe for the most popular Placenta.. Also called libum by the Romans, it was more like a modern day day cheesecake on a pastry base, pie/cake called Placenta often used as an offering to the gods. With the development of the Roman Empire and its efficient road transport, pie cooking spread throughout throughout Europe.[2] Pies remained as a core staple of diet of traveling and working peoples in the colder northern European countries, with regional variations based on both the locally grown and available meats, as well as the locally farmed cereal crop. The Cornish pasty The pasty is an excellent adaptation of the pie to a working man's daily food needs. needs.[2] Medieval cooks were often restricted in cooking forms they were able to use, having restricted access to ovens due to their costs of construction and need for abundant supplies of fuel. Pies could be easily cooked over an open fire, while partnering with a baker allowed them to cook the filling inside their own locally defined casing. The earliest pie-like recipes basket or box box)), with straight sealed sides and a top; open top pies were refer to coffyns (the word actually used for a a basket referred to as traps.This may also be the reason why early recipes focus on the filling over the surrounding case, with the partnership development leading to the use of reusable earthenware pie cases which reduced the use of expensive flour.[6] The first reference to "pyes" as food items appeared in England England (in a a Latin Latin context) as early as the 12th century, but no unequivocal reference to the item with which the article is concerned is attested until the 14th century (Oxford English Dictionary sb pie sb pie)).[2] Song birds at the time were a fine delicacy, and protected by Royal Law. At the coronation of eight-year old English English King Henry VI VI (1422–1461) in 1429, "Partryche and Pecock enhackyll" pie was served, consisting of cooked peacock mounted in cooked peacock its skin on a peacock filled pie. Cooked birds were frequently placed by European royal cooks on top of a large pie to identify its contents, leading to its later adaptation in pre-Victorian times as a porcelain ornament to release of steam and identify a good pie.[2] The Pilgrim fathers and early settlers brought their pie recipes with them to The to America, America, adapting to the ingredients and techniques available to them in the New World. Their first pies were based on berries and fruits pointed out to them by Americans..[2] Pies allowed colonial cooks to stretch ingredients and also used round shallow pans to the the Native North Americans literally "cut corners," and create a regional variation of shallow pie.[7] Regional variations
Apple pie crust pies with fillings such as steak, cheese, Meat pies cheese, steak and kidney kidney,, minced beef , or chicken or chicken and and mushroom are popular in Australiaand and New Zealand as take-away snacks. They are also served with chips chips as an alternative the the United Kingdom,[8] Australia chips at British chip shops. to fish and chips Pot pies pies with a flaky crust and bottom are also a popular American dish, typically with a filling of meat (particularly beef, chicken or turkey), gravy, and mixed vegetables (potatoes, carrots and peas). Frozen pot pies are often sold in individual serving size.
as pie à la mode . Many sweet pies are Fruit pies may be served with a scoop of ice cream, a style known in North America as served this way. Cream, as well as sour cream, is also sometimes considered to be an à la mode serving method as well. [citation needed ]
Apple pie pie is a traditional choice, though any pie with sweet fillings may be served à la mode. mode. This combination,
and possibly the name as well, is thought to have b een popularized in the mid-1890s in the United States. States.[9] Pie throwing
Main article: Pieing Cream filled or topped pies are favorite props for humor. Throwing a pie in a person's face has been a staple of film in Mr. Flip Flip in 1909. 1909.[10] More recently, pieing has also become a political act. comedy since since Ben Turpin Turpin received one in Types of pies
Main article: List of pies Savory pies Chicken Pie A traditional Cornish Cornish pasty pasty filled withsteak withsteak and vegetables
Bacon and egg pie
Butter pie
Chicken and mushroom pie
Corned beef pie
Cottage pie (or shepherds' pie)
Game pie
Fish pie
Hom Homity ity pie
Meat pie
Pasty
Pizza pie
Pork pie
Pot pie
Quiche
Scotch pie
Curry pie
Sta Stargaz rgazy y pie
Steak pie
Steak and kidney pie
Sweet pies Pumpkin pie
Blackberry pie pie and ice cream
Some of these pies are pies in name only, such as the the Boston cream pie, pie, which is a a cake. cake. Many fruit and berry pies are very similar, varying only the fruit used in filling. Fillings for sweet or fruity are often mixed, such as strawberry rhubarb pie.
Apple pie
Ban Banoffe offee e pie
Blackberry pie
Blueberry pie
Buk o pie
Cherry pie
Chess pie
Cream pie
Custard pie
Fried pie
Key lime pie
Lemon meringue pie
Mince pie
Pecan pie
Pumpkin pie
Rhubarb pie
Shoofly pie—a pie filled with molasses
Strawberry pie
Sugar pie
Sweet potato pie
Yeast
Yeast
Yeast of the species Saccharomyces species Saccharomyces cerevisiae
Scientific classification
Domain:
Eukaryota
Kingdom:
Fungi
Phyla and Subphyla
Ascomycota
Saccharomycotina (true yeasts)
Taphrinomycotina
Schizosaccharomycetes(fissio (fissio Schizosaccharomycetes n yeasts)
Basidiomycota
Agaricomycotina
Tremellomycetes
Pucciniomycotina
Microbotryomycetes
micro-organisms classified in the Yeasts are are eukaryotic eukaryotic micro-organisms the kingdom kingdom Fungi, with 1,500 1,500 species species currently described[1] estimated asexually by by mitosis mitosis,, and many do so via an asymmetric division to be only 1% of all fungal species. species .[2] Most reproduce asexually process called budding. Yeasts are unicellular, although some species with yeast forms may become multicellular through false hyphae, as seen in most molds.. or false most molds the formation of a string of connected budding cells known as pseudohyphae, or [3]
Yeast Yeast size can vary greatly depending on the species, typically measuring 3–4 3–4 µm µm in in diameter , although some yeasts
can reach over 40 µm. [4] By By fermentation the yeast species Saccharomyces cerevisiae cerevisiae converts and alcohols - for converts carbohydrates carbohydrates to carbon dioxide dioxide and thousands of years the carbon dioxide has been used in in baking baking and the alcohol in in alcoholic beverages.[5] It is also biology research, and is one of the most thoroughly extremely important as a a model organism organism in modern modern cell biology researched eukaryotic eukaryotic microorganisms. Researchers have used it to gather information about the biology of the albicans,, are are opportunistic eukaryotic cell and ultimately human biology. biology .[6] Other species of yeast, such as Candida albicans pathogens and can cause pathogens in microbial fuel cause infections in humans. Yeasts have recently been used to generate electricity in cells,[7] and produce ethanol for the biofuel industry. cells, Yeasts do not form a single taxonomic or phylogenetic or phylogenetic grouping. The term "yeast" is often taken as for Saccharomyces cerevisiae, cerevisiae,[8] but the phylogenetic diversity of yeasts is shown by their placement in two a synonym synonym for Saccharomyces separate phyla, the Ascomycota and the Basidiomycota. The budding yeasts ("true yeasts") are classified in separate the the order Saccharomycetales.[9] History
See also: also: History of wine wine and History of beer foam,, English gist , gyst , and from the Indo-European root yes- , meaning boil , foam The word "yeast" comes to us from from Old English the Indo-European or or bubble bubble..[10] Yeast microbes are probably one of the earliest domesticated organisms. People have used yeast for fermentation and baking throughout history. Archaeologists digging in Egyptian ruins found early grinding stones and baking chambers for yeasted bread, as well as drawings of 4,000-year-old bakeries and breweries.[11] In 1680, the the Dutch naturalist naturalist Anton van Leeuwenhoek Leeuwenhoek first first microscopically microscopically observed yeast, but at the time did not consider them to organisms ms, but rather globular structures. 1857, French microbiologist microbiologist Louis Pasteur proved in the paper beliving beliving organis structures.[12] In 1857, "Mémoire sur l a fermentation alcoolique" alcoolique" that alcoholic fermentation was conducted by living yeasts and not by a broth, cell growth growth could be increased, but chemical catalyst. catalyst.[11][13] Pasteur showed that by bubbling oxygen into the yeast broth, effect". ". fermentation was inhibited – an observation later called the "Pasteur "Pasteur effect cerevisiae, so called top By the late 18th century, two yeast strains used in brewing had been identified: Saccharomyces cerevisiae, fermenting yeast, and fermenting carlsbergensis,, bottom fermenting fermenting yeast. S. cerevisiae has been sold commercially by the Dutch and S. carlsbergensis for bread making since 1780; while around 1800, the Germans started producing S. cerevisiae in the form of cream. In 1825 a method was developed to remove the liquid so the yeast could be prepared as solid blocks. blocks .[14] The industrial production of yeast blocks was enhanced by the introduction of the filter press press in 1867. In 1872, Baron Max de Springer developed a manufacturing process to create granulated yeast, a technique that was used until the first World War .[15] In the United States, naturally occurring airborne yeasts were used almost exclusively until commercial yeast was marketed at the the Centennial Exposition Exposition in 1876 in Philadelphia, where where Charles L. Fleischmann exhibited the product and a process to use it, as well as serving the resultant baked bread. Nutrition and growth
Yeasts are chemoorganotrophs, as they use use organic compounds compounds as a source of energy and do not require sunlight to glucose and fructose,, or disaccharides such andfructose grow. Carbon is obtained mostly from hexose sugars, such as glucose and maltose maltose.. Some species can metabolize metabolize pentose pentose sugars like ribose,[16] alcohols, and organic acids. Yeast as as sucrose and alcohols, and respiration tion (obligate aerobes), or are anaerobic, but also have aerobic species either require oxygen for aerobiccellular aerobiccellular respira methods of energy production (facultative anaerobes anaerobes)). Unlike bacteria, bacteria, there are no known yeast species that grow only anaerobically (obligate (obligate anaerobes). anaerobes). Yeasts grow best in a neutral or slightly acidic pH environment. Yeasts vary in what temperature range they grow best. For example, Leucosporidium frigidum grows at -2 to 20 °C (28 to 68 °F), Saccharomyces telluris at 5 to 35 °C (41 to 95 °F) and Candida slooffi at at 28 to 45 °C (82 to 113 °F). °F).[17] The cells can survive freezing under certain conditions, with viability decreasing over time. media or in liquid broths.. Common media used for the Yeasts are generally grown in the laboratory on solid growth media liquid broths cultivation of yeasts include include potato dextrose agar (PDA) or potato dextrose broth, Wallerstein Laboratories nutrient peptone dextrose dextrose agar (YPD), and yeast mould agar or broth (YM). Home brewers who cultivate yeast (WLN) agar , yeast peptone andagar as a solid growth medium. The antibiotic antibiotic cycloheximide is sometimes frequently use dried malt extract extract (DME) andagar added to yeast growth media to inhibit the growth of Saccharomyces of Saccharomyces yeasts and select for wild/indigenous yeast species. This will change the yeast process. The appearance of a white, thready yeast, commonly known as kahm yeast, is often a byproduct of the lactofermentation (or pickling) of certain vegetables, usually the result of exposure to air. Although harmless, it can give pickled vegetables a bad flavour and so must be re moved regularly during fermentation.[18] Ecology
Yeasts are very common in the environment, and are often isolated from sugar-rich material. Examples include naturally grapes,, apples apples or peaches), peaches), and exudates from plants (such as occurring yeasts on the skins of fruits and be rries (such as as grapes The ecological ecological function plant saps or cacti). Some yeasts are found in association with soil and insects. insects .[19][20] The biodiversity of yeasts are relatively unknown compared to those of other microorganisms other microorganisms..[21] Yeasts, Yeasts, and biodiversity and rubra, Torulopsis Torulopsis and including Candida albicans, albicans, Rhodotorula rubra, and Trichosporon cutaneum, have been found living in Yeasts are also present in the the gut flora flora of mammals and some between people's toes as part of their skin flora. flora.[22] Yeasts insects[23] and even deep-sea environments host an array of yeasts. yeasts .[24][25] An Indian study of seven bee species and 9 plant species found 45 species from 16 genera colonise the nectaries of flowers and honey stomachs of bees. Most were members of the Candida Candida genus; the most common species in honey stomachs was Dekkera intermedia and in flower nectaries, nectaries, Candida blankii .[26] Yeast colonising nectaries of the the stinking hellebore have been found to raise the temperature of the flower, which may aid in attracting pollinators by increasing the hellebore [21][27]
A black yeast has been recorded as a partner in a complex relationship evaporation of volatile organic compounds. compounds. between ants, between ants, their their mutualistic mutualistic fungus, a fungal parasite of the fungus and a fungal parasite a bacterium bacterium that kills the parasite. The yeast have a negative effect on the bacteria that normally produceantibiotics produce antibiotics to kill the parasite and so may affect the ants' health by allowing the parasite to spread.[28] Reproduction
The yeast cell's life cycle: 1. Budding 2. Conjugation 3. Spore
See also: also: Mating of yeast Yeasts, like all fungi, may have asexual and sexual sexual reproductive cycles. The most common mode of vegetative growth in budding..[29] Here a small bud (also known as a a bleb), bleb), or daughter cell, is formed on the yeast is asexual reproduction by by budding parent cell. The nucleus nucleus of the parent cell splits into a daughter nucleus and migrates into the daughter cell. The bud continues to grow until it separates from the parent cell, forming a new cell.[30] Some yeasts, budding.[29] including Schizosaccharomyces pombe, reproduce by by fission fission instead of budding. Under high stress conditions, conditions, haploid haploid cells will generally die; under the same conditions, however, however, diploid diploid cells can meiosis)) and producing a variety of haploid spores, which can go on undergo sporulation, entering sexual reproduction (meiosis the diploid. diploid.[31] to mate mate (conjugate), reforming the Some pucciniomycete yeasts, particularly species of Sporidiobolus of Sporidiobolus and and Sporobolomyces Sporobolomyces produce aerially dispersed, asexual ballistoconidia.[32] Uses
The useful physiological properties of yeast have led to their use in the field of biotechnology. Fermentation of sugars by yeast is the oldest and largest application of this technology. Many types of yeasts are used for making many ermentation; rmentation; yeast in in wine wine fermentation and foods: baker's yeast yeast in bread bread production; brewer's yeast in beerf e So-called red rice yeast yeast is actually a a mold, mold, Monascus purpureus. purpureus. Yeasts include some of the most for xylitol for xylitol production production..[33] So-called widely used used model organisms organisms for genetics genetics and and cell biology. Alcoholic beverages Alcoholic beverages beverages that contain beverages are defined as as beverages contain ethanol (C2H5OH). This ethanol is almost always produced the metabolism metabolism of of carbohydrates carbohydrates by certain species of yeast under anaerobic or low-oxygen conditions. by by fermentation – the wine,, beer , or distilled or distilled spirits spirits all use yeast at some stage of their production. A d istilled beverage is a Beverages such as wine distillation.. Carbohydrate-containing plant material is fermented by beverage containing ethanol that has been purified by by distillation yeast, producing a dilute solution of ethanol in the process. Spirits such as as whiskey whiskey and rum are prepared by distilling these dilute solutions of ethanol. Components other than ethanol are collected in the condensate, including water, water, esters esters,, flavour of the beverage. and other alcohols other alcohols,, which account for the flavour of Beer Beer being fermented by brewers yeast
fermenting") ") and "bottom cropping" (or "bottom-fermenting "bottom-fermenting"). "). Brewing yeasts may be classed as "top cropping" (or "top " top fermenting [34]
Top cropping yeasts are so called because they form a foam at the top of the wort during fermentation. An example of a
top cropping yeast is Saccharomyces cerevisiae, cerevisiae, sometimes called an "ale yeast". yeast" .[35] Bottom cropping yeasts are typically used to produce produce lager -type beers, though they can also produce ale-type beers. These yeasts ferment well at low carlsbergensis. temperatures. An example of bottom cropping yeast is is Saccharomyces pastorianus, formerly known as S. carlsbergensis. Decades ago, taxonomists reclassified S. carlsbergensis (uvarum) as a member of S. cerevisae, noting that the only distinct difference between the two is metabolic. Lager strains of S. cerevisae secrete an enzyme called melibiase, allowing it to hydrolyse the disaccharide melibiose into more fermentable monosaccharides. Top cropping and bottom cropping, cold fermenting and warm fermenting distinctions are largely generalizations used to by the laymen to communicate to the general public. For more on the taxonomical differences, see Terrance M. Dowhanick, B.SC., PH. D "Yeast - Strains and Handling Techiques" in The Practical Brewer, a publication of the Master Brewers Association of the Americas.
The most common top cropping brewer's yeast, S. cerevisiae, cerevisiae, is the same species as the common baking yeast. [36]
Brewer's yeast is also very rich inessential in essential minerals and the the B vitamins vitamins (except B12). B12).[37] However, baking and brewing
yeasts typically belong to different strains, cultivated to favour different characteristics: baking yeast strains are more aggressive, to carbonate carbonate dough dough in the shortest amount of time possible; brewing yeast strains act slower, but tend to produce fewer off-flavours and tolerate higher alcohol concentrations (with some strains, up to 22%). of Lambic Lambic and specialty sour Dekkera /Brettan /Brettanomyces omyces is a genus of yeast known for their important role in the production of ales,, along with the secondary conditioning of a particular Belgian Trappist beer [38]. The taxonomy of the genus ales Brettanomyces has been debated since its early discovery and has seen many re-classifications over the years. Early classification was based on a few species that reproduced asexually (anamorph form) through multipolar budding budding [39]. Shortly after, the formation of ascospores was observed and the genus Dekkera, which reproduces sexually (teleomorph form), was introduced as part of the taxonomy taxonomy [40]. The current taxonomy includes five species within the genera of Brettanomyces omyces anomal anomalus us,, Brettanomyces Dekkera/Brettanomyces. Those are the anamorphs anamorphs Brettanomyces bruxellensis, bruxellensis,Brettan custersianus,, Brettanomyces naardenensis, and custersianus and Brettanomyces nanus, with teleomorphs existing for the first two species, Dekkera bruxellensis andDekkera andDekkera anomala
[41]
. The distinction between Dekkera and Brettanomyces is arguable
with Oelofse et al. (2008) citing Loureiro and Malfeito-Ferreira from 2006 when they affirmed that current molecular DNA detection techniques have uncovered no variance between the anamorph and teleomorph states. Over the past decade, Brettanomyces spp. have seen an increasing use in the craft-brewing sector of the industry with a handful of breweries having produced beers that were primary fermented with pure cultures of Brettanomyces spp. This has occurred out of experimentation as very little information exists regarding pure culture fermentative capabilities and the aromatic compounds produced by various strains. Dekkera/Brettanomyces spp. have been the subjects of numerous studies conducted over the past century although a majority of the recent research has focused on enhancing the knowledge of the wine industry. Recent research on 8 Brettanomyces strains available in the brewing industry focused on strain specific fermentations and identified the major compounds produced during pure culture anaerobic fermentation in wort. wort.[42] Wine Fermentation (wine) Yeast is used in winemaking, where it converts the sugars present in into ethanol ethanol.. Yeast is normally in grape juice juice (must) must) into already present on grape skins (the white powder called "the bloom"). Fermentation can be done with this endogenous "wild yeast,"[43] but this procedure gives unpredictable results, which depend upon the exact types of yeast species present. For this reason, a pure yeast culture is usually added to the must; must; this yeast quickly dominates the fermentation. The wild yeasts are repressed, which ensures a reliable and predictable fermentation. fermentation .[44] Most added wine yeasts are strains of S. cerevisiae cerevisiae,, though not all strains of the species are suitable. suitable.[44] Different S. cerevisiae yeast strains have differing physiological and fermentative properties, therefore the actual strain of yeast selected can have a direct impact on the finished wine. wine .[45] Significant research has been undertaken into the development of novel wine yeast strains that produce atypical flavour profiles or increased complexity in wines. wines.[46][47] The growth of some yeasts, such as Zygosaccharomyces Zygosaccharomyces and and Brettanomyces, in wine can result in in wine faults and Brettanomycesproduces produces an array of metabolites when growing in wine, some of which are subsequent spoilage.[48] Brettanomyces volatile phenolic phenolic compounds. Together, these compounds are often referred to as "Brettanomyces " Brettanomyces character", and are often described as "antiseptic "antiseptic" or "barnyard" type aromas. Brettanomyces is a significant contributor to to wine faultswithin faultswithin the wine industry. industry.[49] Researchers from from University of British Columbia , Canada Canada,, have found a new strain of yeast that has reduced amines. amines. The and Chardonnay Chardonnay produce off-flavors and cause headaches and hypertension in some people. About 30 amines in in red wine wine and histamines..[50] percent of people are sensitive to biogenic amines, such as as histamines Baking Yeast, most commonly S. cerevisiae, cerevisiae, is used in in baking baking as a a leavening agent, where it converts fermentable sugars sugars present in dough the the fermentable dough into the gas carbon dioxide. dioxide. This causes the dough to expand or rise as gas
forms pockets or bubbles. When the dough is baked, the yeast dies and the air pockets "set", giving the baked product a soft and spongy texture. The use of potatoes, water from potato boiling, eggs, or sugar in a bread dough accelerates the growth of yeasts. Most yeasts used in baking are of the same species common in alcoholic fermentation. Additionally, Saccharomyces exiguus (also known as S. minor ), ), a wild yeast found on plants, fruits, and grains, is occasionally used for baking. Sugar and and vinegar provide the best conditions for yeast to ferment. In bread making, the yeast initially respires aerobically, producing carbon dioxide and water. When the oxygen is depleted, depleted, anaerobic respiration begins, producing ethanol as a waste product; however, this evaporates during baking.[51] respiration It is not known when yeast was first used to bake bread. The first records that s how this use came from Ancient Egypt. [52]
Researchers speculate a mixture of flour meal and water was left longer than usual on a warm day and the yeasts that
occur in natural contaminants of the flour caused it to ferment before baking. The resulting bread would have been lighter and tastier than the normal flat, hard cake. Active dried yeast, a granulated form in which yeast is commercially sold
Today, there are several retailers of baker's yeast; one of the best-known in North America is is Fleischmann’s Yeast, Yeast, which ld War II , Fleischmann's developed a a granulated granulated active dry yeast, which did not require was developed in 1868. DuringWor DuringWorld refrigeration and had a longer shelf life than fresh yeast. The company created yeast that would rise twice as fast, reducing baking time. Baker's yeast yeast is also sold as a fresh yeast compressed into a square "cake". This form perishes quickly, and must therefore be used soon after production. A weak solution of water and sugar can be used to determine if yeast is expired. In the solution, active yeast will foam and bubble as it ferments the sugar into ethanol and carbon dioxide. Some recipes refer to this as proofing the yeast as it "proves" (tests) the viability of the yeast before the other ingredients are added. When using a a sourdough starter, flour and water are added instead of sugar; this is referred to as proofing the sponge. When yeast is used for making bread, it is mixed with flour, salt, and warm water or milk. The dough is kneaded until it is smooth, and then left to rise, sometimes until it has doubled in size. Some bread doughs are kn ocked back after one rising and left to rise again. A longer rising time gives a better flavour, but the yeast can fail to raise the bread in the final stages if it is left for too long initially. The dough is then shaped into loaves, left to rise until it is the correct size, and then baked. Dried yeast is usually specified for use in a bread machine machine;; however, a (wet) sourdough starter can also work. Bioremediation Some yeasts can find potential application in the field of bioremediation bioremediation.. One such yeast, Yarrowia lipolytica, lipolytica, is known to TNT (an explosive material), material),[54] and other hydrocarbons other hydrocarbons, such as alkanes, degrade palm oil degrade oil mill effluent, effluent,[53] alkanes, fatty acids, fats fats and oils oils..[55] It can also tolerate high concentrations of salt and andheav heavy y meta metals ls,,[56] and is being investigated for its potential as a heavy metal biosorbent. biosorbent.[57] Industrial ethanol production The ability of yeast to convert sugar into into ethanol ethanol has been harnessed by the biotechnology biotechnology industry to produce produce ethanol fuel.. The process starts by milling a feedstock, such as fuel as sugar cane, cane, field corn corn,, or other cereal other cereal grains, grains, and then adding amylase enzymes, to break down the starches into complex sugars. A glucoamylase is dilute sulfuric acid, dilute acid, or fungal alpha amylase then added to break the complex sugars down into into simple sugars. After this, yeasts are added to convert the simple distilled off to obtain ethanol up to 96% in concentration concentration..[58] sugars to ethanol, which is then then distilled Saccharomyces yeasts have been genetically engineered to ferment xylose, one of the major fermentable sugars present in in cellulosic biomasses, biomasses, such as agriculture residues, paper wastes, and wood chips chips..[59][60] Such a development means ethanol can be efficiently produced from more inexpensive feedstocks, making cellulosic ethanol fuel a more fuels..[61] competitively priced alternative to gasolinefuels Nonalcoholic beverages A Kombucha culture fermenting in a jar Root beer and other sweet carbonated beverages can be prod uced using the same methods as beer, except the fermentation is stopped sooner, producing carbon dioxide, but only trace amounts of alcohol,
and a significant amount of sugar is left in the drink. Kvass inEastern Kvass,, a fermented drink made from from rye, is popular inEast ern Euro Europe pe; with acetic acid bacteria is used in the preparation it has a recognizable, but low alcoholic content. Yeast in in symbiosis symbiosis with include: Brettanomyces of kombucha of kombucha,, a fermented sweetened sweetened tea. tea. Species of yeast found in the tea can v ary, and may include: bruxellensis,, Candida stellata, bruxellensis stellata,Schizosaccharomyces pombe, Torulaspora delbrueckii and and Zygosaccharomyces bailii . [62]
Kombucha is a popular beverage in Eastern Europe and someformer some former Soviet republic republics s under the name chajnyj
grib (Чайный гриб), which means "tea mushroom". Kefir Kefir and and kumis are made by fermenting milk with yeast and bacteria. [63]
Nutritional supplements See also: Tibicos Yeast is used in nutritional supplements popular with with vegans vegans and the health conscious, where it is often referred to as yeast". ". It is a deactivated yeast, usually S. cerevisiae. cerevisiae. It is an excellent source of protein and vitamins, "nutritional yeast B-complex vitamins, whose functions are related to metabolism, as well as especially the B-complex minerals and cofactors required for growth. It is also naturally low in in fat and and sodium. sodium. Some brands of nutritional other minerals yeast, though not all, are fortified with vitamin B12, which is produced separately by by bacteria. bacteria. Nutritional yeast, though it has a similar appearance to brewer's yeast, is very different and has a very different taste. Brewer's yeast is a good source of B-complex vitamins but, contrary to some claims, it contains little or no no vitamin B12.[64] Nutritional yeast has a nutty, cheesy flavor which makes it popular as an ingredient in in cheese substitutes. It is often used by vegans in place of Parmesan cheese cheese.. Another popular use is as a topping for popcorn. It can also be used in mashed and fried potatoes, as well as in scrambled eggs. It comes in the form of flakes, or as a yellow powder similar in texture to cornmeal, and can be found in the bulk aisle of most natural food stores. In Australia, it is sometimes sold as "savory yeast flakes". Though "nutritional yeast" usually refers to commercial products, inadequately fed prisoners have used "home-grown" yeast to prevent vitamin deficiency deficiency..[65] Probiotics Some probiotic supplements use the yeast to maintain and restore the natural flora in the gastrointestinal yeast S. boulardii tract. S. boulardii has children,[66][67] prevent reinfection boulardii has been shown to reduce the symptoms of acute diarrhea diarrhea in children, difficile,[68] reduce bowel movements in diarrhea-predominant of Clostridium of Clostridium difficile, diarrhea-predominant IBS patients patients,,[69] and reduce the incidence traveler's,,[71] and and HIV/AIDS [72] associated diarrheas. of antibiotic of antibiotic,,[70] traveler's Aquarium hobby aquarium hobbyists to generate in planted aquariums.[73] A Yeast is often used by aquarium generate carbon dioxide dioxide (CO2) to nourish plants in homemade setup is widely used as a cheap and simple alternative to pressurized CO2 systems. While not as effective as these, the homemade setup is considerably cheaper for less demanding hobbyists. There are several recipes for homemade CO 2, but they are variations of the basic recipe: Baker's yeast, with with sugar , baking soda and soda and water , are added to a plastic bottle. A few drops of vegetable oil at the start reduces surface tension and speeds the release of CO2. This will produce CO2 for about 2 or 3 weeks; the use of a bubble counter determines production. The CO2 is injected in the aquarium via a narrow hose and released through a diffuser that helps dissolve the gas in the water. The CO2 is used by plants in the photosynthesis photosynthesis process. Science Diagram showing a yeast cell
Several yeasts, particularly S. cerevisiae, cerevisiae, have been widely used in genetics genetics and cell biology. This is largely humans for the study of because S. cerevisiae is a simple eukaryoticcell, eukaryoticcell, serving as a a model for all eukaryotes, including humans fundamental cellular processes such as the the cell cycle, DNA replication,recombination recombination,, cell division and and metabolism metabolism.. Also, yeasts are easily manipulated and cultured in the laboratory, which has allowed for the development of p owerful standard techniques, such as yeast two-hybrid, synthetic genetic array array analysis and and tetrad analysis. Many proteins important in
homologues in yeast; these proteins include cell cycle human biology were first discovered by studying their homologues proteins, signaling proteins, and protein-processing protein-processing enzymes. On 24 April 1996 S. cerevisiae was announced to be the first eukaryote to have its genome, consisting of 12 million base pairs, fully sequenced as part of the Genome project.[74] At the time, it was the most complex organism to have its full genome sequenced, and took seven years and the involvement of more than 100 laboratories to accomplish accomplish..[75] The second yeast species to have its genome sequenced was was Schizosaccharomyces pombe, which was completed in 2002.[76][77] It was the sixth eukaryotic genome sequenced and consists of 13.8 million base pairs. Yeast extract Main article: Yeast extract Marmite and Marmite and Vegemite, Vegemite, products made from from yeast extract Marmite and Vegemite have a distinctive dark colour
Yeast extract is the common name for various forms of processed yeast p roducts that are used as as food additives or flavours. additives or flavours. They are often used in the same way that that monosodium glutamate glutamate (MSG) is used, and like MSG, often contain free glutamic acid. The general method for making yeast extract for food products such and Marmite Marmite on a commercial scale is to add salt to a suspension of yeast making the solution hypertonic, as as Vegemite and digestive enzymes break their which leads to the cells shrivelling up. This triggers autolysis, where the yeast's yeast's digestive ownproteins down into simpler compounds, a process of self-destruction. The dying yeast cells are then heated to ownproteins complete their breakdown, after which the husks (yeast with thick cell walls which would give poor texture) are separated. Promite (Australia) Australia); Marmite Marmite,, Bovril and and Oxo (the (the United Kingdom, Republic of Yeast autolysates are used in in Vegemite Vegemite and andPromite Ireland and South Africa Ireland Africa)); and Cenovis (Switzerland Switzerland). ). Pathogenic yeasts
A photomicrograph photomicrograph of Candida albicans albicansshowing showing hyphal outgrowth and other morphological characteristics.
pathogens where they can cause infection in people with compromised Some species of yeast are are opportunistic pathogens compromised immune systems. Cryptococcus neoformans is a significant pathogen of immunocompromised people causing the disease termed cryptococcosis. This disease occurs in about 7–9% of AIDS of AIDS patients in the USA, and a slightly smaller percentage polysaccharide capsule, which helps to (3–6%) in western Europe. Europe.[78] The cells of the yeast are surrounded by a rigid polysaccharide prevent them from being recognised and engulfed by by white blood cells in the human body. Yeasts of the the Candida Candida genus are another group of opportunistic pathogens which causes oral and vaginal vaginal infections infections in membranes of humans humans, known as candidiasis.Candida candidiasis.Candida is commonly found as a commensal yeast in the the mucus membranes and other warm-blooded animals. However, sometimes these same strains can become pathogenic. Here the yeast cells sprout a hyphal outgrowth, which locally penetrates the the mucosal membrane, membrane, causing irritation and shedding of the tissues.[78] The pathogenic yeasts of candidiasis in probable descending order of virulence for humans are: C. albicans, albicans, C. tropicalis, C. stellatoidea stellatoidea,, C. glabrata, C. krusei , C. parapsilosis, C. guilliermondii , C. viswanathii , C. lusitaniae and and Rhodotorula mucilaginosa. [79]Candida glabrata is the second most common Candida pathogen after C. after C. bloodstream((candidemia). candidemia).[80] the bloodstream albicans,, causing infections of the urogenital tract, and of the albicans Food spoilage
Yeasts are able to grow in foods with a low pH, (5.0 or lower) and in the presence of sugars, organic acids and other easily metabolized carbon sources. sources.[81] During their growth, yeasts metabolize some food components and produce metabolic end products. This causes the physical, chemical, and sensible properties of a food to change, and the food is spoiled.[82] The growth of yeast within food products is often seen on their surface, as in cheeses cheeses or meats or meats,, or by the fermentation of as syrups and and jams. jams.[81] The yeast of sugars in beverages, such as juices as juices,, and semi-liquid products, such as the the Zygosaccharomyces Zygosaccharomyces genus have had a long h istory as a spoilage yeast within the food industry. This is mainly due to
ethanol,, acetic acid acid,, sorbic acid, acid, benzoic acid acid,, the fact that these species can grow in the presence of high high sucrose, sucrose, ethanol and sulphur dioxide dioxide concentrations,[83] representing some of the commonly used used food preservationmethods. Methylene blue is used to test for the presence of live yeast cells.