WINETECH Technical Yearbook 2021

OENOLOGY RESEARCH | MARCH 2021

IT CAN HAPPEN TO THE YOUNGEST and most experienced of winemakers alike – what we thought would be our boldest vintage for decades, has come out lighter in colour than we expected. Rather than the intense red and violet that we anticipated, we’re greeted with a wine that’s pale red, pitiful orange or even brown. Head hung in shame, we wonder what we could have done differently to get the colour we’re after. Don’t let wine tannins leave you bitter – let’s see how we can make your red wine blush again! ABOUT TANNINS Polyphenols are important contributors to wine. They play important roles in astringency, colour, mouthfeel and taste. Tannins are a group of polyphenols consisting of bitter and astringent compounds readily found in nature. They’re present in tea, coffee, cacao, and in plants, they’re found in the bark, leaves, fruit and seeds. The tannins in plants play an important role in survival by acting as a defence mechanism when eaten. The tannins bind to, and precipitate, proteins on the tongue causing a dry, unpleasant and astringent taste deterring any hungry and unsuspecting victim. Similarly, grape tannins react with compounds found in wine including proteins, polysaccharides and colour compounds

Wine tannins and polysaccharides – frenemies? JAMES DUNCAN: South African Grape and Wine Research Institute, Department of Viticulture and Oenology, Stellenbosch University, Stellenbosch KEYWORDS: Polyphenols, tannins, anthocyanins, polysaccharides, enzymes.

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