Taming the tannin tiger

"Pinotage gets a bad rap” says Gyles Webb at Thelema. “The most tannic red cultivar in SA is Merlot.” One he nevertheless gets right with his Reserve 2008, my favourite by the proverbial country mile.

Tannin is a bitter substance contained in the skin, pips and the odd vine twig that makes its way into the fermenting vat. Tannins are also supplied by the oak barrels used to age most red wines and are an important factor in determining longevity.

When they come into contact with the proteins of the tongue, cheek and lips, a chemical tanning process is initiated, which explains why your mouth feels like an old shoe after tasting a lineup of aggressive reds. In fact, the word tannin comes from the ancient Celtic name for the chemical they used to treat animal skins to make leather for service in their coracles, shoes and sporrans, with the verb ‘to tan’ having the same root.

Over time, tannins precipitate out of red wine leaving behind ‘wine diamonds’ and giving the aged liquid a smoother and rounder character. Making red wine is essentially a balancing act between providing sufficient tannins for ageing and minimising the astringent taste of the compound. Passing oxygen through a wine, a process called microoxygenation, had been effectively used by some producers to soften tannins in aggressive young wines, providing an earlydrinking character without compromising on maturation potential.

For irredeemably tannic horrors, adding egg white or isinglass, an exotic substance extracted from the bladders of freshwater fish or even good old bentonite (a potter’s clay) can improve the situation. This process, called fining, also removes some of the longer chain flavour molecules, so is used at the winemaker’s peril.

Tannin content determines those handwaving terms like ‘palate weight’ and ‘mouthfeel’ in the winespeak lexicon. While supplying the dominant tactile component, tannins are not alone in providing a sense of touch to a wine. Fats often have no flavour, but when they press against a taste bud they produce a tactile sensation that is interpreted by the brain as slippery or greasy. The combination of the two can be magic.

Aussie Shiraz superstar Steven Henschke, whose Hill of Grace is arguably the greatest achievement of Shiraz Down Under, describes the tannins of his finest Shiraz as “slippery”. ‘Round’ is a geometric term often used by compilers of wine tasting laundry lists, while ‘hard’ is a negative description used to denote bitterness.

One left-field explanation for the tannic excesses of some Merlots comes from the Boere Buddha of Biodynamism, Johan Reyneke, and is based on the observation that plants communicate with each other. While not yet up to replying to Prince Charles when he asks their advice, stressed plants release pheromones that are picked up by other plants in a form of an early warning system.

“When our cows break out from their corral, I always walk upwind to find them. Cows know they must walk upwind because when plants get chomped they release pheromones to warn their neighbours and produce tannin to become bitter and unpalatable. Cows walk upwind to outwit plants.”

Could Johan’s insights be used to combat tannin triggering during harvest? Merlot is typically planted in orderly rows, so if harvested into the prevailing wind, vines will have less time to mobilise their tannin defences. Tannin management in the vineyards rather than postfacto manipulation of the wine is a less interventionist strategy and conforms to our notions of authenticity, a vital characteristic for a terroirdriven product looking for a selling point in an ocean of commercial wine made in industrial quantities.