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]
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.
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.
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]
^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
^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)
^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, INIST13441184
^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
^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
^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. ISBN0-8412-3729-8.
