Wine chemistry

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280 nm 45 min LC chromatogram of a red wine, showing mainly phenolic compounds. Chromato vin rouge.PNG
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 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. [1]

Contents

Environmental factors such as soil, rainfall and fog affect flavor in ways that can be described collectively as "character" or the French term “terroir”. [1] 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 secondary compounds develop during the growing season can be disrupted. Hotter temperatures and an earlier growing season can push chemistry of berries towards higher sugar content, less acids and differences in aromas. [1] Other factors such as smoke taint from fires [1] can negatively impact chemistry and flavor, resulting in flaws and wine faults that can make the wines undrinkable.

Types of natural molecules present in wine

Volatiles

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 additionPermitted additives
Acidificationtartaric acid
Clarificationcalcium 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

Decolourantspolyvinyl-polypyrrolidone (PVPP)

activated charcoal

Deacidificationlactic bacteria

neutral potassium tartrate
potassium bicarbonate
calcium carbonate

Deodorantcopper sulfate
Elaborationoak chips

metatartaric acid
water

Enrichmentconcentrated grape must

rectified concentrated grape must
saccharose
tannin
oxygen

Enzymesbetaglucanase

pectolytics
urease

Fermentationfresh lees

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

Sequestrantsfresh lees

potassium ferrocyanide
calcium phytate
citric acid

Stabilisationcalcium 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

2,4,6-trichloroanisole, the chemical primarily responsible for cork taint in wines. 2,4,6-Trichloroanisole.svg
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 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 adversely affect it. 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 (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 Brettanomyces produces an array of metabolites when growing in wine, some of which are volatile phenolic compounds. Brettanomyces converts p-coumaric acid to 4-vinylphenol via the enzyme cinnamate decarboxylase. [15] 4-Vinylphenol is further reduced to 4-ethylphenol by the enzyme 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.

Geraniol is a by-product of the metabolism of sorbate.

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

See also

Notes

  1. 1 2 3 4 Chrobak, Ula; Zimmer, Katarina (22 June 2022). "Climate change is altering the chemistry of wine". Knowable Magazine. doi: 10.1146/knowable-062222-1 . Retrieved 11 July 2022.
  2. 1 2 3 Villamor, Remedios R.; Ross, Carolyn F. (28 February 2013). "Wine Matrix Compounds Affect Perception of Wine Aromas". Annual Review of Food Science and Technology. 4 (1): 1–20. doi:10.1146/annurev-food-030212-182707. ISSN   1941-1413. PMID   23464569 . Retrieved 11 July 2022.
  3. Monoterpenes in grape juice and wines. M. Jiménez, Journal of Chromatography A, Volume 881, Issues 1–2, 9 June 2000, Pages 557–567, 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. Using LC-MSMS To Assess Glutathione Levels in South African White Grape Juices and Wines Made with Different Levels of Oxygen. Wessel Johannes Du Toit, Klemen Lisjak, Maria Stander and Dersiree Prevoo, J. Agric. Food Chem., 2007, Vol. 55, No. 8, doi : 10.1021/jf062804p
  7. Straightforward Method To Quantify GSH, GSSG, GRP, and Hydroxycinnamic Acids in Wines by UPLC-MRM-MS. Anna Vallverdú-Queralt, Arnaud Verbaere, Emmanuelle Meudec, Veronique Cheynier and Nicolas Sommerer, J. Agric. Food Chem. 2015, 63, 142−149, doi : 10.1021/jf504383g
  8. Günata, Ziya; Wirth, Jérémie L.; Guo, Wenfei; Baumes, Raymond L. (2001). "C13-Norisoprenoid Aglycon Composition of Leaves and Grape Berries from Muscat of Alexandria and Shiraz Cultivars". In Winterhalter, Peter; Rouseff, Russell L. (eds.). Carotenoid-Derived Aroma Compounds. ACS Symposium Series. Vol. 802. p. 255. doi:10.1021/bk-2002-0802.ch018. ISBN   0-8412-3729-8.
  9. P. Winterhalter, M. A. Sefton and P. J. Williams (1990). "Volatile C13-Norisoprenoid Compounds in Riesling Wine Are Generated From Multiple Precursors". Am. J. Enol. Vitic. 41 (4): 277–283. doi:10.5344/ajev.1990.41.4.277. S2CID   101007887.
  10. Zelena, Kateryna; Hardebusch, Björn; Hülsdau, BäRbel; Berger, Ralf G.; Zorn, Holger (2009). "Generation of Norisoprenoid Flavors from Carotenoids by Fungal Peroxidases". Journal of Agricultural and Food Chemistry. 57 (21): 9951–5. doi:10.1021/jf901438m. PMID   19817422.
  11. Cabaroglu, Turgut; Selli, Serkan; Canbas, Ahmet; Lepoutre, Jean-Paul; Günata, Ziya (2003). "Wine flavor enhancement through the use of exogenous fungal glycosidases". Enzyme and Microbial Technology. 33 (5): 581. 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. Lamont, Kim T.; Somers, Sarin; Lacerda, Lydia; Opie, Lionel H.; Lecour, Sandrine (2011). "Is red wine a SAFE sip away from cardioprotection? Mechanisms involved in resveratrol- and melatonin-induced cardioprotection". Journal of Pineal Research. 50 (4): 374–80. doi:10.1111/j.1600-079X.2010.00853.x. PMID   21342247. S2CID   8034935.
  14. M. Baldy "The University Wine Course" Third Edition pgs 37-39, 69-80, 134-140 The Wine Appreciation Guild 2009 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

Related Research Articles

<span class="mw-page-title-main">Vin jaune</span> Type of French white wine from the Jura region

Vin jaune is a special and characteristic type of white wine made in the Jura region in eastern France. It is similar to dry fino Sherry and gets its character from being matured in a barrel under a film of yeast, known as the voile, on the wine's surface. Vin jaune shares many similarities with Sherry, including some aromas, but unlike Sherry, it is not a fortified wine. The wine is made from the Savagnin grape, with some of the most premium examples coming from the marl based vineyards in the Château-Chalon AOC. In other French wine regions, there has been experimentation in producing similar style wines from Chardonnay and other local grape varieties using cultured yeast such as the vin de voile wine produced in the Gaillac.

A wine fault is a sensory-associated (organoleptic) characteristic of a wine that is unpleasant, and may include elements of taste, smell, or appearance, elements that may arise from a "chemical or a microbial origin", where particular sensory experiences might arise from more than one wine fault. Wine faults may result from poor winemaking practices or storage conditions that lead to wine spoilage.

<span class="mw-page-title-main">3-Methylbutanoic acid</span> Carboxylic acid with chemical formula (CH3)2CHCH2CO2H CH3CH2

3-Methylbutanoic acid, also known as β-methylbutyric acid or more commonly isovaleric acid, is a branched-chain alkyl carboxylic acid with the chemical formula (CH3)2CHCH2CO2H. It is classified as a short-chain fatty acid. Like other low-molecular-weight carboxylic acids, it has an unpleasant odor. The compound occurs naturally and can be found in many foods, such as cheese, soy milk, and apple juice.

<i>p</i>-Coumaric acid Chemical compound

p-Coumaric acid is an organic compound with the formula HOC6H4CH=CHCO2H. It is one of the three isomers of hydroxycinnamic acid. It is a white solid that is only slightly soluble in water but very soluble in ethanol and diethyl ether.

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.

<span class="mw-page-title-main">4-Ethylguaiacol</span> Chemical compound

4-Ethylguaiacol, often abbreviated to 4-EG, is a phenolic compound with the molecular formula C9H12O2. It can be produced in wine and beer by Brettanomyces. It is also frequently present in bio-oil produced by pyrolysis of lignocellulosic biomass.

<span class="mw-page-title-main">Muscat of Alexandria</span> Variety of grape

Muscat of Alexandria is a white wine grape that is a member of the Muscat family of Vitis vinifera. It is considered an "ancient vine", and wine experts believe it is one of the oldest genetically unmodified vines still in existence. The grape originated in North Africa, and the name is probably derived from its association with Ancient Egyptians who used the grape for wine making. It is also a table grape used for eating and raisins.

<span class="mw-page-title-main">Fermentation in winemaking</span> Wine making process

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.

<span class="mw-page-title-main">2-Methoxy-4-vinylphenol</span> Chemical compound

2-Methoxy-4-vinylphenol is an aromatic substance used as a flavoring agent. It is one of the compounds responsible for the natural aroma of buckwheat.

<span class="mw-page-title-main">Phenolic content in wine</span> Wine chemistry

The phenolic content in wine refers to the phenolic compounds—natural phenol and polyphenols—in wine, which include a large group of several hundred chemical compounds that affect the taste, color and mouthfeel of wine. These compounds include phenolic acids, stilbenoids, flavonols, dihydroflavonols, anthocyanins, flavanol monomers (catechins) and flavanol polymers (proanthocyanidins). This large group of natural phenols can be broadly separated into two categories, flavonoids and non-flavonoids. Flavonoids include the anthocyanins and tannins which contribute to the color and mouthfeel of the wine. The non-flavonoids include the stilbenoids such as resveratrol and phenolic acids such as benzoic, caffeic and cinnamic acids.

<span class="mw-page-title-main">Aroma of wine</span> Olfactory sensation of wine

The aromas of wine are more diverse than its flavours. The human tongue is limited to the primary tastes perceived by taste receptors on the tongue – sourness, bitterness, saltiness, sweetness and savouriness. The wide array of fruit, earthy, leathery, floral, herbal, mineral, and woodsy flavour present in wine are derived from aroma notes sensed by the olfactory bulb. In wine tasting, wine is sometimes smelled before taking a sip in order to identify some components of the wine that may be present. Different terms are used to describe what is being smelled. The most basic term is aroma which generally refers to a "pleasant" smell as opposed to odour which refers to an unpleasant smell or possible wine fault. The term aroma may be further distinguished from bouquet which generally refers to the smells that arise from the chemical reactions of fermentation and aging of the wine.

This glossary of winemaking terms lists some of terms and definitions involved in making wine, fruit wine, and mead.

<span class="mw-page-title-main">Clarification and stabilization of wine</span> Wine clarification and stabilisation

In winemaking, clarification and stabilization are the processes by which insoluble matter suspended in the wine is removed before bottling. This matter may include dead yeast cells (lees), bacteria, tartrates, proteins, pectins, various tannins and other phenolic compounds, as well as pieces of grape skin, pulp, stems and gums. Clarification and stabilization may involve fining, filtration, centrifugation, flotation, refrigeration, pasteurization, and/or barrel maturation and racking.

<span class="mw-page-title-main">Caftaric acid</span> Chemical compound

Caftaric acid is a non-flavonoid phenolic compound.

<span class="mw-page-title-main">Ripeness in viticulture</span> How the term "ripe" is used in viticulture and winemaking

In viticulture, ripeness is the completion of the ripening process of wine grapes on the vine which signals the beginning of harvest. What exactly constitutes ripeness will vary depending on what style of wine is being produced and what the winemaker and viticulturist personally believe constitutes ripeness. Once the grapes are harvested, the physical and chemical components of the grape which will influence a wine's quality are essentially set so determining the optimal moment of ripeness for harvest may be considered the most crucial decision in winemaking.

<span class="mw-page-title-main">Grape reaction product</span> Chemical compound

The grape reaction product is a phenolic compound explaining the disappearance of caftaric acid from grape must during processing. It is also found in aged red wines. Its enzymatic production by polyphenol oxidase is important in limiting the browning of musts, especially in white wine production. The product can be recreated in model solutions.

4-Vinylphenol is an organic compound with the formula C2H3C6H4OH. It is the most studied of the three isomeric vinylphenols. It is a white volatile solid.

Vinylphenol reductase is an enzyme that catalyses the reaction :

<span class="mw-page-title-main">Yeast in winemaking</span> Yeasts used for alcoholic fermentation of wine

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. 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.

4-Hydroxycinnamate decarboxylase is an enzyme that uses p-coumaric acid to produce 4-ethylphenol.

References