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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.
Brettanomyces is a non-spore forming genus of yeast in the family Saccharomycetaceae, and is often colloquially referred to as "Brett". The genus name Dekkera is used interchangeably with Brettanomyces, as it describes the teleomorph or spore forming form of the yeast, but is considered deprecated under the one fungus, one name change. The cellular morphology of the yeast can vary from ovoid to long "sausage" shaped cells. The yeast is acidogenic, and when grown on glucose rich media under aerobic conditions, produces large amounts of acetic acid. Brettanomyces is important to both the brewing and wine industries due to the sensory compounds it produces.
Malolactic conversion is a process in winemaking in which tart-tasting malic acid, naturally present in grape must, is converted to softer-tasting lactic acid. Malolactic fermentation is most often performed as a secondary fermentation shortly after the end of the primary fermentation, but can sometimes run concurrently with it. The process is standard for most red wine production and common for some white grape varieties such as Chardonnay, where it can impart a "buttery" flavor from diacetyl, a byproduct of the reaction.
Ethanol fermentation, also called alcoholic fermentation, is a biological process which converts sugars such as glucose, fructose, and sucrose into cellular energy, producing ethanol and carbon dioxide as by-products. Because yeasts perform this conversion in the absence of oxygen, alcoholic fermentation is considered an anaerobic process. It also takes place in some species of fish where it provides energy when oxygen is scarce.
Pichia pastoris is a species of methylotrophic yeast. It was found in the 1960s, with its feature of using methanol as a source of carbon and energy. After years of study, P. pastoris was widely used in biochemical research and biotech industries. With strong potential for being an expression system for protein production, as well as being a model organism for genetic study, P. pastoris has become important for biological research and biotech applications. In the last decade, some reports reassigned P. pastoris to the genus Komagataella with phylogenetic analysis, by genome sequencing of P. pastoris. The genus was split into K. phaffii, K. pastoris, and K. pseudopastoris.
A wine fault or defect is an unpleasant characteristic of a wine often resulting from poor winemaking practices or storage conditions, and leading to wine spoilage. Many of the compounds that cause wine faults are already naturally present in wine but at insufficient concentrations to be of issue. In fact, depending on perception, these concentrations may impart positive characters to the wine. However, when the concentration of these compounds greatly exceeds the sensory threshold, they replace or obscure the flavors and aromas that the wine should be expressing. Ultimately the quality of the wine is reduced, making it less appealing and sometimes undrinkable.
The following outline is provided as an overview of and topical guide to wine
Pichia is a genus of yeasts in the family Saccharomycetaceae with spherical, elliptical, or oblong acuminate cells. Pichia is a teleomorph, and forms hat-shaped, hemispherical, or round ascospores during sexual reproduction. The anamorphs of some Pichia species are Candida species. The asexual reproduction is by multilateral budding.
D-Xylose is a five-carbon aldose that can be catabolized or metabolized into useful products by a variety of organisms.
The process of fermentation in winemaking turns grape juice into an alcoholic beverage. During fermentation, yeasts transform sugars present in the juice into ethanol and carbon dioxide. In winemaking, the temperature and speed of fermentation are important considerations as well as the levels of oxygen present in the must at the start of the fermentation. The risk of stuck fermentation and the development of several wine faults can also occur during this stage, which can last anywhere from 5 to 14 days for primary fermentation and potentially another 5 to 10 days for a secondary fermentation. Fermentation may be done in stainless steel tanks, which is common with many white wines like Riesling, in an open wooden vat, inside a wine barrel and inside the wine bottle itself as in the production of many sparkling wines.
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.
American wild ale generally refers to beers brewed in America using yeast or bacteria in addition to Saccharomyces cerevisiae for fermentation. Such beers may be similar to traditional beers such as Lambic and Oud bruin, and are typically fermented using a strain of brettanomyces for part or all of the fermentation. The use of brettanomyces can result in a "funky" flavor profile. Examples include Jolly Pumpkin Perseguidor, Avery 15 and Brabant, and Ommegang Ommegeddon.
Brettanomyces claussenii is a wild yeast of the genus Brettanomyces which has a negative Pasteur effect. It and Brettanomyces anomalus share identical mtDNA. In the wild, it is found on the skins of fruit. It has been shown to be useful for wine and beer fermentation as well as ethanol production.
Wine is a complex mixture of chemical compounds in a hydro-alcoholic solution with a pH around 4.
The role of yeast in winemaking is the most important element that distinguishes wine from grape juice. In the absence of oxygen, yeast converts the sugars of wine grapes 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.
Yeast assimilable nitrogen or YAN is the combination of free amino nitrogen (FAN), ammonia (NH3) and ammonium (NH4+) that is available for the wine yeast Saccharomyces cerevisiae to use during fermentation. Outside of the fermentable sugars glucose and fructose, nitrogen is the most important nutrient needed to carry out a successful fermentation that doesn't end prior to the intended point of dryness or sees the development of off-odors and related wine faults. To this extent winemakers will often supplement the available YAN resources with nitrogen additives such as diammonium phosphate (DAP).
Aerobic fermentation or aerobic glycolysis is a metabolic process by which cells metabolize sugars via fermentation in the presence of oxygen and occurs through the repression of normal respiratory metabolism. It is referred to as the Crabtree effect in yeast. and is part of the Warburg effect in tumor cells. While aerobic fermentation does not produce adenosine triphosphate (ATP) in high yield, it allows proliferating cells to convert nutrients such as glucose and glutamine more efficiently into biomass by avoiding unnecessary catabolic oxidation of such nutrients into carbon dioxide, preserving carbon-carbon bonds and promoting anabolism.
Pichia anomala is a species of ascomycete and teleomorphic fungi of the genus Pichia. It is used as a preventive for undesirable fungi or mold, nevertheless it may spoil food in large quantities. It is used in wine making, airtight stored grain, apples, and grapevines. P. anomala has been reclassified as Wickerhamomyces anomalus.
Dr. Linda Bisson is a trained yeast geneticist who focuses on sugar catabolism and fermentation. She is a retired professor and geneticist from the University of California at Davis.
References
- ↑ "Metschnikowia pulcherrima | Viticulture & Enology". wineserver.ucdavis.edu. Archived from the original on 2014-10-10.
- ↑ Balch, Oliver (2015-02-17). "Scientists reveal revolutionary palm oil alternative: Yeast". The Guardian.
- ↑ "Metschnikowia pulcherrima | Viticulture & Enology". wineserver.ucdavis.edu. Archived from the original on 2014-10-10.
- ↑ Oro, L; Ciani, M; Comitini, F (2014). "Antimicrobial activity of Metschnikowia pulcherrima on wine yeasts". J. Appl. Microbiol. 116 (5): 1209–17. doi: 10.1111/jam.12446 . PMID 24443784.
- ↑ Türkel, Sezai; Korukluoğlu, Mihriban; Yavuz, Mümine (2014). "Biocontrol Activity of the Local Strain of Metschnikowia pulcherrima on Different Postharvest Pathogens". Biotechnology Research International. 2014: 1–6. doi: 10.1155/2014/397167 . PMC 4016867 . PMID 24860671.
- ↑ Contreras, A; Curtin, C; Varela, C (2015). "Yeast population dynamics reveal a potential 'collaboration' between Metschnikowia pulcherrima and Saccharomyces uvarum for the production of reduced alcohol wines during Shiraz fermentation". Appl. Microbiol. Biotechnol. 99 (4): 1885–95. doi:10.1007/s00253-014-6193-6. PMID 25388943. S2CID 16279623.
- ↑ "Hello, my name is Metschnikowia pulcherrima". 2015-06-22.
- ↑ "Announcements".
- ↑ "A palm oil substitute and care product emulsions from a yeast cultivated on waste resources - Opus". opus.bath.ac.uk. Archived from the original on 2016-03-26.
- ↑ Jenkins, Rhodri W. (2015). "Cross-Metathesis of Microbial Oils for the Production of Advanced Biofuels and Chemicals". ACS Sustainable Chemistry & Engineering. 3 (7): 1526–1535. doi: 10.1021/acssuschemeng.5b00228 .
