Wine chemistry

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280 nm 45 min LC chromatogram of a red wine, showing mainly phenolic compounds.

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

Tannins add bitterness and astringency which acts to defend vines against pests and grazing animals.[1]

Environmental factors such as soil, rainfall and fog affect flavor in ways that can be described collectively as "character" or the French term “

wine faults
that can make the wines undrinkable.

Types of natural molecules present in wine

Volatiles

Main article: Aroma of wine
  • Methoxypyrazines
  • Esters:[2] Ethyl acetate is the most common ester in wine, being the product of the most common volatile organic acid — acetic acid, and the ethyl alcohol generated during the fermentation.
  • glycosidases.[11]

Other molecules found in wine

Preservatives

Fining agents

Gum arabic has been used in the past as fining agent.[12]

List of additives permitted for use in the production of wine under European Union law:

Type or purpose of addition Permitted additives
Acidification tartaric acid
Clarification calcium alginate

potassium alginate
potassium caseinate
casein
isinglass
silicon dioxide
edible gelatine
acacia (gum arabic)
milk/lactalbumin
proteins of plant origin
ovalbumin (egg white)
alumino silicates
ferrous sulfate

Decolourants polyvinyl-polypyrrolidone (PVPP)

activated charcoal

Deacidification lactic bacteria

neutral potassium tartrate
potassium bicarbonate
calcium carbonate

Deodorant copper sulfate
Elaboration oak chips

metatartaric acid
water

Enrichment concentrated grape must

rectified concentrated grape must
saccharose
tannin
oxygen

Enzymes betaglucanase

pectolytics
urease

Fermentation fresh lees

ammonium bisulphite
thiamine hydrochloride
yeast cell walls
yeasts for wine production
diammonium phosphate
ammonium sulphate
ammonium sulphite

Sequestrants fresh lees

potassium ferrocyanide
calcium phytate
citric acid

Stabilisation calcium tartrate

potassium bitartrate
yeast mannoproteins
Preservatives sorbic acid
sulphur dioxide
argon
nitrogen
potassium bisulphite
dimethyl dicarbonate (DMDC)
carbon dioxide
potassium metabisulphite/disulfite
allyl isothiocyanate
lysozyme
potassium sorbate
ascorbic acid

Others

Wine faults

Main article: Wine fault
2,4,6-trichloroanisole, the chemical primarily responsible for cork taint
in wines.

A wine fault or defect is an unpleasant characteristic of a wine often resulting from poor

aromas that the wine should be expressing (or that the winemaker wants the wine to express). Ultimately the quality of the wine is reduced, making it less appealing and sometimes undrinkable.[14]

The yeast

vinyl phenol reductase. 4-Ethylphenol causes a wine fault at a concentration of greater than 140 μg/L. Other compounds produced by Brettanomyces that cause wine faults include 4-ethylguaiacol and isovaleric acid
.

Coumaric acid is sometimes added to microbiological media, enabling the positive identification of Brettanomyces by smell.

sorbate
.

Fusel alcohols are a mixture of several alcohols (chiefly amyl alcohol) produced as a by-product of alcoholic fermentation.

See also

Notes

  1. ^
    doi:10.1146/knowable-062222-1
    . Retrieved 11 July 2022.
  2. ^
    PMID 23464569
    . Retrieved 11 July 2022.
  3. doi:10.1016/S0021-9673(99)01342-4
  4. ^ Terpenes in the aroma of grapes and wines: A review. J. Marais, S. Afr. J. Enol. Vitic., 1983, volume 4, number 2, pages 49-58 (article)
  5. ^ Inhibition of the decline of linalool and α-terpineol in muscat wines by glutathione and N-acetyl-cysteine. Papadopoulou D. and Roussis I. G., Italian journal of food science, 2001, vol. 13, no4, pages 413-419, INIST 13441184
  6. doi:10.1021/jf062804p
  7. doi:10.1021/jf504383g
  8. ISBN 0-8412-3729-8
    .
  9. S2CID 101007887
    .
  10. PMID 19817422
    .
  11. doi:10.1016/S0141-0229(03)00179-0
    .
  12. ^ Vivas N, Vivas de Gaulejac N, Nonier M.F and Nedjma M (2001). "Incidence de la gomme arabique sur l'astringence des vins et leurs stabilites colloidales" [Effect of gum arabic on wine astringency and colloidal stability]. Progres Agricole et Viticole (in French). 118 (8): 175–176.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  13. S2CID 8034935
    .
  14. ISBN 0-932664-69-5
  15. ^ Brettanomyces Monitoring by Analysis of 4-ethylphenol and 4-ethylguaiacol Archived 2008-02-19 at the Wayback Machine at etslabs.com

References

  • Comprehensive Natural Products II — Chemistry and Biology, chapter 3.26 – Chemistry of Wine, volume 3, pages 1119–1172. Véronique Cheynier, Rémi Schneider, Jean-Michel Salmon and Hélène Fulcrand,
    doi:10.1016/B978-008045382-8.00088-5

External links

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