Would you like pepper in your shiraz?
I well recall the first ‘peppery’ Aussie shiraz I ever tasted. It was Knight’s Granite Hills 1980 Shiraz, from the chilly Macedon Ranges.
It was impressive first and foremost because of its aroma, and we sold truckloads of it at the shop where I used to work in 1983.
These days, pepper is an accepted part of the aroma of cool-climate shiraz, and the Australian Wine Research Institute (AWRI) is leading the world on the compound that gives wine this aroma, which is called rotundone.
According to Tracey Siebert, an AWRI research scientist working in this field, about 20-25% of humans cannot smell rotundone. This is not unusual with aromas: many people have blind spots for various odours. But rotundone is powerful stuff: the human threshold (the lowest concentration at which we can detect an aroma) for rotundone in water is 8 nanograms per litre, which is something like three drops in an Olympic-sized swimming pool. It takes a bit more for us to pick it up in red wine: 16 ng/l.
“Rotundone is most likely to come from shiraz, and from cool-climate regions.”
Siebert told a recent NSW Department of Primary Industries shiraz workshop in the Hunter Valley.
The Grampians region has a lot of it – in fact, Mount Langi Ghiran Vineyard (tastings) is involved in AWRI trials on rotundone in shiraz and regularly produces the highest readings. It’s a matter of record that Mount Langi Ghiran’s late winemaker Trevor Mast was first smitten with the vineyard when he smelled the shiraz grapes fermenting and was seduced by the peppery aroma.
Other regions where shiraz is peppery are the Canberra District, Adelaide Hills, Coonawarra, Great Southern, Geelong, all of Western Victoria, and New Zealand’s Hawkes Bay.
Siebert says the rotundone resides in the skin of the grape, but no other part of it.
“During ripening, it arrives late – in the few weeks just before harvest. This is quite unlike the capsicum/green pepper aroma, which arrives in the grape early.”
In other words, pepper is not a sign of unripe or underripe grapes, as some critics have suggested.
“Another unusual feature of rotundone is that it’s found in the grape and makes its way into the wine unaltered by fermentation,” she says.
This is very different from other aroma compounds, which are either formed or modified during fermentation.
Siebert says the amount of rotundone varies widely according to the season. It is weather, or temperature, related. Cooler years/climates produce more rotundone.
I clearly recall the late great Gérard Jaboulet, of Paul Jaboulet Aîné (tastings) in the Rhône Valley (maker of the famous Hermitage La Chapelle), saying back in the late 1980s that he regarded pepper as a negative characteristic, and a sign of unripe grapes. Perhaps he associated it with unripe grapes because in unripe years – which they had plenty of in his region in the 1970s – the grapes do have lots of rotundone. But there is nothing unripe about Mount Langi Ghiran shirazes, Siebert confirms.
Indeed, the AWRI also works with a French vineyard in the Gaillac region, where the local grape duras is a high-rotundone variety. The duras had high levels of rotundone in the difficult, unripe year like 2014, while the warmer, riper 2013 vintage showed much lower levels.
The Langi vineyard showed an amazing 40-fold difference in levels of rotundone between the highest and lowest readings. The cooler, more shaded parts of the vineyard had more rotundone than the more exposed parts. Irrigation was also found to increase the peppery factor.
The next thing some enterprising student could do is conduct research into whether rotundone affects perceived wine quality. It seems to me, tasters who are used to rich, chocolaty shiraz (say from Barossa Valley) tend to like peppery shiraz less, while those who drink a lot of Yarra Valley or other Victorian shiraz enjoy it more. In other words, conditioning has a big influence on our enjoyment of such wines.
*First published in Gourmet Traveller WINE magazine, February-March 2017.