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Vinylphenol Reductase
Vinylphenol reductase is an enzyme that catalyses the reaction : 4-vinylphenol + NAD+ + 3 H+ ⇔ 4-ethylphenol + NADH It is found in ''Brettanomyces bruxellensis'', a yeast responsible of the presence of ethyl phenols in wine formed from p-coumaric acid. See also * Wine chemistry * Yeast in winemaking The role of yeast in winemaking is the most important element that distinguishes wine from fruit juice. In the :wikt:anaerobic, absence of oxygen, yeast converts the sugar in wine, sugars of the fruit into ethanol, alcohol and carbon dioxide throu ... References External links Vinylphenol reductase on MetaCyc Oxidoreductases {{enzyme-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nicotinamide Adenine Dinucleotide
Nicotinamide adenine dinucleotide (NAD) is a coenzyme central to metabolism. Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine nucleobase and the other nicotinamide. NAD exists in two forms: an oxidized and reduced form, abbreviated as NAD and NADH (H for hydrogen), respectively. In metabolism, nicotinamide adenine dinucleotide is involved in redox reactions, carrying electrons from one reaction to another. The cofactor is, therefore, found in two forms in cells: NAD is an oxidizing agent – it accepts electrons from other molecules and becomes reduced. This reaction, also with H+, forms NADH, which can then be used as a reducing agent to donate electrons. These electron transfer reactions are the main function of NAD. However, it is also used in other cellular processes, most notably as a substrate of enzymes in adding or removing chemical groups to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
4-ethylphenol
Ethylphenol (4-EP) is an organic compound with the formula C2H5C6H4OH. It is one of three isomeric ethylphenols. A white solid, it occurs as an impurity in xylenols and as such is used in the production of some commercial phenolic resins. It is also a precursor to 4-vinylphenol. Natural occurrences In wine and beer, 4-EP is produced by the yeast ''Brettanomyces''. At concentrations greater than 140 μg/L (typical sensory threshold) it gives the wine aromas described as ''barnyard'', ''medicinal'', ''band-aids'', and ''mousy''. In certain Belgian beer styles, a high 4-EP level may be desirable; however, very high levels of the compound in wine can render it undrinkable. The level of 4-EP is roughly proportional to ''Brettanomyces'' concentration and activity, and can therefore be used as an indicator of the yeast's presence. There are significant differences between strains of ''Brettanomyces'' in their ability to produce 4-EP. 4-EP is also a component of castoreum, the e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NADH
Nicotinamide adenine dinucleotide (NAD) is a coenzyme central to metabolism. Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine nucleobase and the other nicotinamide. NAD exists in two forms: an oxidized and reduced form, abbreviated as NAD and NADH (H for hydrogen), respectively. In metabolism, nicotinamide adenine dinucleotide is involved in redox reactions, carrying electrons from one reaction to another. The cofactor is, therefore, found in two forms in cells: NAD is an oxidizing agent – it accepts electrons from other molecules and becomes reduced. This reaction, also with H+, forms NADH, which can then be used as a reducing agent to donate electrons. These electron transfer reactions are the main function of NAD. However, it is also used in other cellular processes, most notably as a substrate of enzymes in adding or removing chemical groups t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brettanomyces Bruxellensis
''Brettanomyces bruxellensis'' (the anamorph of ''Dekkera bruxellensis'') is a yeast associated with the Zenne, Senne valley near Brussels, Belgium. Despite its Latin species name, ''B. bruxellensis'' is found all over the globe. In the wild, it is often found on the skins of fruit. Beer production ''B. bruxellensis'' plays a key role in the production of the typical Belgian beer styles such as lambic, Flanders red ales, gueuze and Kriek lambic, kriek, and is part of spontaneous Beer fermentation, fermentation biota. It is naturally found in the brewery environment living within oak barrels that are used for the storage of beer during the secondary conditioning stage. Here it completes the long slow fermentation or super-attenuation of beer, often in symbiosis with ''Pediococcus sp''. Macroscopically visible colonies look whitish and show a dome-shaped aspect, depending on the age and size. ''B. bruxellensis'' is increasingly being used by American craft brewers, especially in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wine Chemistry
Wine is a complex mixture of chemical compounds in a hydro-alcoholic solution with a pH around 4. The chemistry of wine and its resultant quality depend on achieving a balance between three aspects of the berries used to make the wine: their sugar content, acidity and the presence of secondary compounds. Vines store sugar in grapes through photosynthesis, and acids break down as grapes ripen. Secondary compounds are also stored in the course of the season. Anthocyanins give grapes a red color and protection against ultraviolet light. Tannins add bitterness and astringency which acts to defend vines against pests and grazing animals. Environmental factors such as soil, rainfall and fog affect flavor in ways that can be described collectively as "character" or the French term “terroir”. As climate change disrupts long-established patterns of temperature and precipitation in wine-growing regions and causes more extreme weather events, the rate at which sugars, acids and seconda ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yeast In Winemaking
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.Jeff Cox ''"From Vines to Wines: The Complete Guide to Growing Grapes and Making Your Own Wine"'' pp. 133–36 Storey Publishing 1999 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.D. Bird ''"Understanding Wine Technology"'' pp. 67–73 DBQA Publishing 2005 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 unintenti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
