Spotlight on pepper in Shiraz

If you love the pepperiness of Shiraz/Syrah, you probably already know that this is down to rotundone. This organic compound was discovered in 2008¹ but in May 2023 when researchers at the Australian Wine Research Institute (AWRI) sequenced the genome of Shiraz, they finally identified the genetic variants ‘which when combined with appropriate environmental triggers may allow Shiraz to produce high levels of rotundone²’.

Scroll down to see tasting notes for three Mount Langi Ghiran Shiraz wines to try

A peppery hallmark

Scientists already knew that cooler climatic conditions helped to highlight pepperiness but now wine-growers and winemakers can feel vindicated to have a genetic basis for the synthesis of this sesquiterpene. One estate in particular – Mount Langi Ghiran in the Grampians in Victoria, Australia – has become known for its peppery taste and sees it as a ‘hallmark’, especially of its most famous wine, the Langi Shiraz, harvested from its oldest vineyard block.

Part of the story

For Damien Sheehan, viticulturist at Mount Langi Ghiran, the new research shows that there is something special about the Shiraz clone in the Old Block vineyard. It was planted in 1969 with cuttings from a 140-year-old nursery block, also in the Grampians.

‘We tend to use our own vines for propagation rather than rely on the commercially available clones, partly because we found some clones do not seem to be very spicy compared to our own, so I guess this discovery supports that experience. We knew the day would come when the mystery of pepper in Shiraz would be revealed. Pepper, when in balance, is such an exciting and alluring character in wine that for Langi it acts as a point of recognition,’ he says. However, he is keen to stress that: ‘Pepper, as exciting as it is, is just a part of the whole story.’

A complete array of flavours

Sheehan also notes that while pepperiness has become a recognised and desired feature in Mount Langi Ghiran’s flagship wine, it is not an end in itself since it ‘can be present without much other flavour expression and with unripe tannins’.

‘If we get pepper character into the bargain we are happy but count it as a bonus. We don’t intentionally pursue pepperiness in our Shiraz. Our main target is to capture optimal ripeness, meaning a more complete array of flavours combined with fully ripened tannins,’ he says.

The pepperiness of rotundone and its expression in wine, especially in Shiraz, has captured interest, simply because the compound is so potent: most of us can perceive it in tiny concentrations of 8ng/L in water and 16ng/L in red wine – a nanogram is a billionth of a gram – even if around 20% of people cannot smell or taste it at all³. But those of us who can perceive it and like it tend to seek it out.

Mount Langi Ghiran Shiraz: a trio to try

1. Wood, C. et al, From Wine to Pepper: Rotundone, an Obscure Sesquiterpene, Is a Potent Spicy Aroma Compound, Journal of Agricultural and Food Chemistry 2008 56 (10), 3738-3744
2. Onetto, C. et al, The Genome Assembly of Vitis vinifera cv. Shiraz, Australian Journal of Grape and Wine Research, vol. 2023, Article ID 6686706, 14 pages, 2023
3. Wood, C. et al, From Wine to Pepper: Rotundone, an Obscure Sesquiterpene, Is a Potent Spicy Aroma Compound, Journal of Agricultural and Food Chemistry 2008 56 (10), 3738-3744

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