Intro to wine chemistry
A wine tasting event can be a very awkward yet fun situation to most people. The vast majority of wines produced for the global market are pretty simple, and show little complexity of aromas, flavours, or colour – think entry level supermarket white wines for instance. Pleasant, but forgettable. Some on the contrary display layers of complexity, both on the nose and palate. These are the wines most likely to call on our olfactive memories, resulting in much pleasure and emotion. An endless list of descriptors can be used when assessing the quality of a wine: fruity, floral, earthy, woody, buttery... We have discussed the nature of wine in our very first post, and we know grapes are the main constituent of wine.
From a chemical point of view, the key components in wines are:
- About 98% of Water and Ethanol. A 12% ABV wine will contain approximately 86% water and 12% alcohol. Usually the higher alcohol by volume, the heavier, warmer the wine.
- Dissolved gas: naturally incurring during fermentation – or added by the winemaker - CO2 and Sulphur Dioxide* (SO2, or sulfites).
- Phenolics: or polyphenols. A large group of chemical compounds with a phenol- base, largely responsible for colour, tannins, flavours and some aromas.
- Acids: tartaric, malic, lactic, succinic, citric… partly responsible for the actual and perceived acidity level, texture and some flavours
- Sugars: 'residual sugar' stands for the sugar that was not consumed by the yeasts during fermentation. Usually pretty low, but higher in commercial reds and sparkling, and much higher in sweet and fortified wines.
- Glycerol: sugar (although technically an alcohol) produced during fermentation which gives viscosity, an oily texture and extra sweetness to the wine – easily spotted in the famous legs or tears against the glass!
- Other volatile substances: esters and other alcohols, acetaldehydes, acetic acid…Mostly impact the aromas in a wine, not all are pleasant. Can make a wine smell of vinegar.
- Minerals: salts, potassium, calcium, and iron. Nothing to do with the minerality or saltiness of a wine, which have more to do with acidity and aromas.
- Potential residues of pesticides, herbicides, fertilisers or additives, in small quantities.
There is a popular belief that a glass of red a day would protect from heart disease or cancer. Polyphenol antioxidants naturally occurring in the grape’s skin have been studied for many years, and this has now been scientifically proven to be a myth. Resveratrol is a name that comes up all the time, but then again, its concentration in wine is too low to have any proven positive impact. Rather than the wine itself, it’s the lifestyle and diet associated with wine-drinking countries around the Mediterranean that's showing the most positive impact of health and wellbeing. In short, the healthiest glass of wine there possibly is is the one we pair with a balanced meal, we responsibly share with our loved ones and appreciate in a relaxed and safe setting.