Riesling

Riesling has a strong claim to being the greatest white wine grape, and an equally strong claim to being the most misunderstood. Its reputation in English-speaking markets was damaged by decades of cheap sweet German exports, and it has never fully recovered, which is why some of the finest white wine in the world remains among the best value.

The case for it rests on three things. First, acidity: Riesling retains searing natural acid even at high ripeness, which is what allows it to make wines from bone dry to intensely sweet without ever tasting flabby. Second, transparency — like Pinot Noir it transmits site with unusual clarity, and the difference between slate, quartzite and limestone is legible in the glass. Third, longevity. A good Riesling ages for decades, and low alcohol, often between eight and twelve per cent, is no obstacle to that.

The Mosel is the reference, where steep slate slopes angled towards the sun ripen fruit at latitudes that should not work at all, producing wines of piercing acidity, low alcohol and intense lime-and-green-apple fruit. The Rheingau and Nahe give fuller, firmer versions; Alsace and Austria's Wachau make it dry and powerful; Australia's Clare and Eden Valleys produce a bone-dry style with lime and a hard mineral edge.

With age it develops the note universally described as petrol or kerosene, from a compound called TDN. It sounds like a fault and is a marker of quality.

It is genetically a cross involving Gouais Blanc, the same undistinguished parent that produced Chardonnay and Gamay.

The sweetness question is the single biggest obstacle to the grape's popularity, and the labelling does not help. German terms describe ripeness at harvest rather than sweetness in the bottle, so a Spätlese may be sweet or dry depending on the producer. The word trocken means dry and is the reliable marker; the VDP's Grosses Gewächs designation indicates a dry wine from a top site.

Even the sweeter styles are rarely cloying, because the acidity is so high that sugar reads as balance rather than sweetness. A Mosel Kabinett at nine per cent alcohol with forty grams of residual sugar tastes fresh rather than sticky, which is difficult to believe until you try it.

Its ageing behaviour is unusual: Riesling develops rather than fades, and the petrol note that appears after five to ten years is a marker of correct development. Bottles from the 1970s and earlier are still vivid, and the grape is almost always sealed under screwcap now precisely to protect that trajectory.