How to spot Cabernet Sauvignon blind, in one glass

There is a moment in every blind tasting where you stop sniffing and start feeling. Cabernet Sauvignon is the grape that rewards that switch, because it announces itself through architecture: the way it dries the gum line, the way the finish keeps going after the fruit has faded. Learn that shape once and you carry it with you for life.

The 2017 Boekenhoutskloof Stellenbosch Cabernet Sauvignon is a good teacher because nothing in it is exaggerated. It is the grape spoken clearly rather than shouted, which is exactly what you want when you are training your palate. So let's use one bottle as the worked example, and build up the grape from there.

It begins with a very small berry

Almost everything distinctive about Cabernet traces back to fruit size. The berries are small and thick-skinned, with a low juice-to-skin ratio, and skin is where colour, tannin and aroma live. More skin per drop of juice means more of all three.

Stellenbosch encourages that in its own particular way. Cold, damp Cape winters push the vines into deep dormancy, and cool, moist springs slow the start of the growing season so the fruit is never rushed. Drier, moderate weather through flowering and into the warmer months lets ripening happen gradually and evenly, while cool evenings hold on to freshness.

So when you swirl this wine and the colour clings to the glass in a deep, opaque core, that is not a stylistic decision made in a cellar. That is small-berry concentration, and it is your first clue. The Boekenhoutskloof team hand-pick and cool the fruit before it is destemmed and crushed, precisely so all that skin material arrives in the tank intact.

The tannin is the fingerprint

Take a proper mouthful and pay attention to where you feel it. Cabernet tends to grip at the front of the mouth, along the gums and the inside of the upper lip, with a fine, sandy drag rather than a coarse one. In this wine the tannins are finely knit, so the sensation is firm without being rough, and it lingers well past the point where you have swallowed.

Now notice the other half of the equation. There is bright acidity running underneath, and it is what stops all that structure feeling heavy. Tannin plus acidity, both in serious quantity, is the combination that makes Cabernet Sauvignon one of the great ageing grapes.

That is the blind-tasting shorthand: if the wine feels built rather than poured, if it has a skeleton you could describe with your hands, you are almost certainly in Cabernet territory.

Where the graphite line comes from

Ask a Cape winemaker what marks out top Stellenbosch Cabernet and someone will say graphite. It reads as a dry, mineral, pencil-lead streak that cuts straight down the middle of the fruit, and once you have found it you will hunt for it every time.

This bottling draws on two contrasting sites to get there: north-west-facing slopes on the Helderberg and a south-east-facing slope at Vlottenburg. Opposite aspects means the two parcels see the sun at different times and ripen differently, so the blend has both generosity and tension in it.

Underneath the vines is deep decomposed granite mixed with Table Mountain sandstone and the ironstone locals call koffieklip. Add the mild maritime influence drifting off the cool False Bay coast, and you get the minerality and the graphite-edged profile that anchor this wine to its own patch of Stellenbosch. Plenty of Cabernet tastes of Cabernet; this one tells you where it grew as well. Terroir is easy to be sceptical about until you taste two wines from the same variety and only one of them has this line through it.

Boekenhoutskloof Stellenbosch Cabernet Sauvignon in the vineyards of South Africa, the

What the barrel adds, and what it cannot fake

Cabernet is one of the few grapes that can genuinely absorb new oak, and this is where the variety's tannin earns its keep. After a cold soak and spontaneous fermentation in tulip-shaped concrete tanks, the wine goes through a slow, natural malolactic fermentation in barrel and then settles for twenty-two months in sixty per cent new French oak, lightly toasted and long-seasoned, from the coopers Sylvain and Saury.

On a lighter red that regime would flatten the fruit entirely. Here it behaves like seasoning, adding a savoury frame around the dark fruit and graphite rather than sitting on top of it. Gentle pump-overs and occasional delestage do the extraction, which is a deliberately unhurried approach to a grape that responds badly to being forced.

The result is the claret-like style that gets talked about with the best Stellenbosch reds: refined, savoury, structured. Tim Atkin MW and Wine Enthusiast both landed on 94, and Platter's gave it 4.5/5 stars, which is a useful sanity check on your own palate rather than a reason to drink it.

Pouring it in late august

Serve it at 17 degrees, which in a British house in August means a short spell in the fridge door rather than straight off the shelf. Give it an hour in a decanter and the structure loosens its shoulders.

While the evenings are still just about warm enough, a chargrilled ribeye with peppercorn sauce is the easiest way to see the tannins do their job: fat and char on one side, that graphite line cutting through on the other. If you want more ideas along those lines, our thoughts on a red for the tail end of the grilling season are a decent starting point.

Come autumn, this is a slow-braised oxtail wine, or a venison casserole with juniper, or a rare roast rib of beef with red-wine gravy on a Sunday. A wedge of mature farmhouse Cheddar works too, and takes less effort. And if you would rather wait: eight to twelve years in the rack will trade some of that fruit for cigar box and earth, with a savoury complexity building underneath, which is Cabernet's other great trick.

If you want one bottle that teaches you the grape properly, the Boekenhoutskloof Stellenbosch Cabernet Sauvignon is the one we hand to people learning to taste, and the one we open when there is beef on the table. Decant it, pay attention to the gum line and the graphite, then put a second bottle somewhere dark and forget about it for a decade.