You’d think these two classic grape varieties, Syrah and Cabernet Sauvignon, would be distinctive enough not to confuse in a blind tasting. And, perhaps, for some people they are. In the Wine Grapes tome, Jancis Robinson MW, writes that the two varieties have very different profiles (see below for more on this).
However, despite this, I’ve muddled the two up plenty of times and have seen lots of really good tasters do it too. I remember a famous Northern Rhone producer (I won’t say which) who called his own wine a Margaux in a blind tasting of Northern Rhone and Left Bank Bordeaux!
Of all the red grapes, Syrah (or Shiraz) appears most frequently in the Master of Wine tasting exam. Twenty-two Syrahs have featured in 11 of the previous 13 MW exams. The message here is, if you’re sitting the MW exam know your Syrah inside out – there’s at least an 84% chance one will feature.
Cabernet Sauvignon dominant blends appear more often than Syrah although not quite as frequently. Twenty-four Cabernet Sauvignon dominant blends appear in 10 of the last 13 red papers. If you’re sitting the MW exam, there’s a good 77% chance a Cab dominant blend will feature.
Both of these varieties are also highly likely to appear on the same exam. Nine of the 10 times Cabernet has been on there so has Syrah. So, it’s really important to be able to tell these varieties apart.
Both grape varieties have thick highly pigmented skins and capable of producing deeply coloured, full bodied, structured, and tannic wines. The two varieties can also be aromatically very similar. Both can show similar dark fruit characteristics (blackberry and blackcurrent, for example). And, both have an affinity for new oak.
A distinguishing feature of Syrah is its high levels of a rotundone — the compound responsible for it’s peppery notes. It’s found in several varieties but Syrah has particularly high levels (Gruner Veltliner is another variety with particularly high levels). The levels of rotundone in Syrah are influenced by a number of factors including clone, harvest date, crop load, and sun exposure. Generally, though, Syrah from cooler climates are likely to have higher levels of rotundone. The Australian Wine Research Institute have published a couple of good papers on the rotundone in Australian and NZ Shiraz that can be found here and here.
Similarly, Cabernet Sauvignon has higher levels of methoxypyrazines than most varieties. This can give it a distinctive green, herbaceous, or vegetal character often described as grassy, bell pepper, herbal or leafy. High levels of this compound is also found in Sauvignon Blanc. Like with rotundone in Syrah, there’s a variety of factors that influence methoxypyrazine level, with exposure to sunlight and ripeness level being two of the most important.
Notes of licorice, olives, and cured meats are common in Syrah. Whereas things like cedar, pencil shavings, and cigar box are often noted in Cabernet Sauvignon. But, what do you do if neither rotundone nor methoxypyrazine nor any other distinctive aromas or flavours are particularly dominant?
Structure can also provide significant evidence. Both can be high in tannin. However, a tight, firm, aristocratic tannic structure is considered a hallmark for Cabernet. Whereas, density and mid-palate richness combined with rounder, gentler tannins is more classic of Syrah.
Wynns – Black Label – Coonawarra Shiraz
Wynns – Black Label – Coonawarra Cabernet Sauvignon
I thought this would be a good comparison that really shows varietal difference. Both made by the same producer, in the same region, and are both the same quality level.
Both of these wines had a very deep, almost opaque, colour; aromatics of ripe dark fruits; concentrated flavours on the palate, and a high level of tannins.
However, the Cabernet had more focused acid with tighter, firmer, and finer tannins. The Shiraz, on the other hand, had softer rounder tannins with more obvious/more pronounced mid palate.
I didn’t find any distinctive peppery rotundone or herbaceous pyrazine notes on either of these wines. And, when tasting them semi-blind it was the structural elements that helped me tell them apart. For less ripe versions it may be the aromatics that gives the biggest clue.