Naturally occurring acids are present in all fruits. The major acids found in grapes are malic and tartaric. When the grape juice is fermented to become wine, these acids survive the fermentation process to end up in the bottle you’re about to open.
Acidity in wine plays a very important role in the overall structural harmony of the drink. Acid is required to balance residual sugar and alcohol. It also cuts through oils and fats present in food, providing the ideal palate cleanser between mouthfuls. An ideal wine will have a balanced acidity. Too much acid and the wine can be unpleasantly tart or sharp tasting; too little and it can taste ‘flabby’ or not as refreshing as it should.
The way in which we perceive acidity varies according to a number of factors. Different grape varieties will have different concentrations of acids, thus can taste more or less ‘acidic’. The climatic conditions throughout the growing season are also important – insufficient warmth or sunlight will mean the acids in the grapes do not ‘soften’ enough before harvest and the resulting wine may be tart and unpleasant. Other organic chemicals in the wine will also influence how we perceive acidity. Two wines may have the same pH, yet a wine with residual sugar that masks the immediate effect of the acid will come across as less acidic initially.
Practices in the winery can also change the acidity in the final wine from that we might expect in the initial grape juice. Malic acid can be converted to lactic acid, which comes across as a ‘softer’ acid on the palate, through a malolactic conversion by certain species of bacteria. Most red wines undergo a malolactic conversion (sometimes called a ‘fermentation’, though this is not strictly correct), which is why red wines often taste softer than whites.
In general we can register acidity by a tingling sensation on the sides of our tongue. Another approach is the ‘saliva response test’ – how quickly saliva returns to our mouth immediately after spitting or swallowing the wine. This can give us clues as to the grape variety, the growing conditions and the sorts of food the wine might pair well with.
Join James Flewellen and Jonell Galloway at “Celebrate the Chartres Festival of Lights & Autumnal Equinox with a Food & Wine Tasting Masterclass” in France from September 19 to 22, 2013.
Dr James Flewellen is a biophysicist at the University of Oxford. James learned his trade in taste through the Oxford Blind Wine Tasting Society, of which he was the President from 2010-2012. During his term, he represented Oxford at many international blind tasting competitions – twice winning the prestigious ‘Top Taster’ Award in the annual Varsity blind tasting match against Cambridge University and captaining winning teams in competitions throughout Europe.
One of James’s goals is to clarify the complex and hard-to-navigate world of wine for both novice and experienced tasters. He applies his scientific training to wine education, illuminating concepts of taste, tannin and terroir in an approachable, entertaining manner. James runs wine education courses in Oxford through the Oxford Wine Academy and is completing the WSET Professional Diploma in Wine and Spirits. He is the regular wine writer for The Rambling Epicure and is the founder of The Oxford Wine Blog. He is also currently co-authoring The Concise Guide to Wine and Blind Tasting – a book surveying the wine regions of the world and how to blind taste.