Sauvignon Blanc

Sauvignon Blanc is the most immediately recognisable white wine grape in the world, and it owes that to chemistry. Its aromas come largely from thiols and methoxypyrazines — compounds the human nose detects at vanishingly small concentrations — which is why a glass announces itself across a room as gooseberry, cut grass, blackcurrant leaf, grapefruit and, at the extreme, something close to tinned asparagus.

The pyrazines diminish as the grape ripens, so picking date largely determines style. Early picking gives the green, herbaceous register; later picking pushes towards passionfruit, guava and white peach.

Two regions define the poles. The Loire, in Sancerre and Pouilly-Fumé, gives a taut, mineral, smoke-and-flint expression on limestone and silex soils, where restraint is the point and the wine is built around acidity. Marlborough in New Zealand, since the 1980s, gives the opposite: pungent, tropical, unmissable fruit, a style so commercially successful that it reshaped global expectations of what the grape should taste like.

Bordeaux takes a third route, blending it with Sémillon and often fermenting in barrel, which builds texture and tames the aromatics into something considerably more serious and longer-lived. The best white Graves age for twenty years.

Oak divides opinion sharply. Fumé Blanc, a name Robert Mondavi coined in California in the 1960s, denotes a barrel-influenced style that softens the grape's edges. Purists consider it a waste of what makes the variety distinctive.

It is genetically a parent of Cabernet Sauvignon, crossed naturally with Cabernet Franc in Bordeaux — which explains the blackcurrant-leaf note shared across all three.

The thiol compounds that give the grape its aroma are unstable and oxygen-sensitive, which explains several things about how it is made and sold. It is bottled young, almost always under screwcap, and it should be drunk within two or three years — the passionfruit and grapefruit notes fade noticeably after that.

The pyrazine and thiol balance is essentially a picking decision, and it is why the same clone gives asparagus-and-grass in one place and passionfruit-and-guava in another. Marlborough's combination of long sunlight hours and cold nights produces unusually high concentrations of both, which is why the style is so emphatic.

The Loire and Bordeaux versions age in a way the New World ones do not, particularly when barrel-fermented and blended with Sémillon. A good white Graves at fifteen years has almost nothing in common with a young Marlborough wine, and anyone who has decided they dislike the grape has usually only met one of its faces.