Wine

Wine

Wine is an alcoholic beverage, made of fermented fruit juice, usually from grapes. The natural chemical balance of grapes lets them ferment without the addition of sugars, acids, enzymes, or other nutrients. Grape wine is produced by fermenting crushed grapes using various types of yeast. Yeast...

 is a complex mixture of chemical compounds in a hydro-alcoholic solution with a pH around 3.

Types of natural molecules present in wine

• Acids in wine
  Acids in wine
  The acids in wine are an important component in both winemaking and the finished product of wine. They are present in both grapes and wine, having direct influences on the color, balance and taste of the wine as well as the growth and vitality of yeasts during fermentation and protecting the wine...
  
  
• Phenolic compounds in wine
  Phenolic compounds in wine
  The phenolic compounds - natural phenol and polyphenols - in wine include a large group of several hundred chemical compounds that affect the taste, color and mouthfeel of wine. These compounds include phenolic acids, stilbenes, flavonols, dihydroflavonols, anthocyanins, flavanol monomers and...
  
  
• Proteins in wine
  Proteins in wine
  Proteins are present in wine. The most common proteins include thaumatin-like proteins and chitinases and have a role in the formation of turbidity especially visible in white wine. The quantity of haze forming is dependant on the quantity of phenolics in the wine.Some of those proteins are...
  
  
• Sugars in wine
  Sugars in wine
  The sugars in wine grapes are what make winemaking possible. During the process of fermentation, sugars are broken down and converted by yeasts into alcohol and carbon dioxide. Grapes accumulate sugars as they grow on the grapevine through the translocation of sucrose molecules that are produced...
  
  
• Tryptophol
  Tryptophol
  Tryptophol is a chemical compound that induces sleep in humans. It is formed in the liver after disulfiram treatment. It is also produced by the trypanosomal parasite in sleeping sickness....
  
   and amino acids derivatives
• Methoxypyrazines
  Methoxypyrazines
  Methoxypyrazines are a class of chemical compounds that produce odors. The odors tend to be undesirable, as in the case of certain wines, or as in the case of the Asian Lady Beetle which produces isopropyl methoxy pyrazine . They have also been identified as additives in cigarette manufacture...
  
   and other volatiles

Other molecules found in wine

• Sulfur dioxide
  Sulfur dioxide
  Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...
  
   (SO₂), a conservative often added to wine

Biochemistry

4-Ethylphenol

4-Ethylphenol

4-Ethylphenol, often abbreviated to 4-EP, is a phenolic compound with the molecular formula C8H10O. In wine and beer it is produced by the spoilage yeast Brettanomyces. When it reaches concentrations greater than the sensory threshold it can give the wine aromas described as barnyard, medicinal,...

 is produced from the precursor p-coumaric acid

Coumaric acid

Coumaric acid is a hydroxycinnamic acid, an organic compound that is a hydroxy derivative of cinnamic acid. There are three isomers, o-coumaric acid, m-coumaric acid, and p-coumaric acid, that differ by the position of the hydroxy substitution of the phenyl group...

. Brettanomyces

Brettanomyces

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. The cellular morphology of...

converts this to 4-vinylphenol

4-Vinylphenol

4-Vinylphenol is a phenolic compound found in wine and beer. It is produced by the spoilage yeast Brettanomyces. When it reaches concentrations greater than the sensory threshold, it can give the wine aromas described as barnyard, medicinal, band-aids, and mousy...

 via the enzyme cinnamate decarboxylase. 4-Vinylphenol is further reduced to 4-ethylphenol by the enzyme vinyl phenol reductase. Coumaric acid is sometimes added to microbiological media

Growth medium

A growth medium or culture medium is a liquid or gel designed to support the growth of microorganisms or cells, or small plants like the moss Physcomitrella patens.There are different types of media for growing different types of cells....

, enabling the positive identification of Brettanomyces by smell.

See also

• Winemaking
  Winemaking
  Winemaking, or vinification, is the production of wine, starting with selection of the grapes or other produce and ending with bottling the finished wine. Although most wine is made from grapes, it may also be made from other fruit or non-toxic plant material...
  
  
• Food chemistry
  Food chemistry
  Food chemistry is the study of chemical processes and interactions of all biological and non-biological components of foods. The biological substances include such items as meat, poultry, lettuce, beer, and milk as examples...
  
  
• Cork taint
  Cork taint
  Cork taint is a broad term referring to a wine fault characterized by a set of undesirable smells or tastes found in a bottle of wine, especially spoilage that can only be detected after bottling, aging and opening...
  
  
• Alternative wine closures
  Alternative wine closures
  Alternative wine closures are substitute closures used in the wine industry for sealing wine bottles in place of traditional cork closures. The emergence of these alternatives has grown in response to quality control efforts by winemakers to protect against "cork taint" caused by the presence of...
  
  
• Premature oxidation
  Premature oxidation
  Premature oxidation, is a flaw that occurs in white wines, when the presumably ageworthy wine is expected to be in good condition yet is found to be oxidised and often undrinkable. In particular the affliction has received attention in connection to incidents of whites produced in Burgundy...
  
  

External links

• Wine Chemistry and Biochemistry. M. Victoria Moreno-Arribas,Carmen Polo,María Carmen Polo, on Google books