High sugar levels do not, on their own, constitute ripeness. On the face of it, it seems a silly question. We all know the difference between a ripe plum and an unripe one. But take the analogy of bananas. Some people consider a banana to be ripe when the skin is yellow all over. To others, a ripe banana has a skin speckled with black. In wine, a grape that is considered ripe in Champagne would be thought unripe in the Napa Valley. The high acid/low sugar ‘ripeness’ that is crucial for making sparkling wines of balance and vivacity in Champagne makes painfully acidic table wines.

High sugar levels

Napa’s sun-soaked grapes make full-bodied table wines but would make fat, flabby fizz. High sugar levels do not, on their own, constitute ripeness. A ripe grape has brown seeds, not green, and the stalk is lignified to the first joint of the bunch. When you taste it (and all good wine producers judge ripeness by taste first, and by analysis second), a red grape should have minimal vegetal green bean flavour, and its skin tannins should be soft and velvety. In other words, the aim is physiological ripeness, and in warmer climates this occurs at higher sugar levels than in cooler climates, simply because it cannot be hurried. Heat will speed up sugar formation; but for tannin ripeness you simply have to wait. This is why ripe grapes in Australia’s Barossa will tend to produce more alcoholic wines than grapes of similar physiological ripeness in Bordeaux. The battle in warm regions is to attain full physiological ripeness without head-banging levels of alcohol: get the equation wrong and you end up with over 15 per cent alcohol and you still get unripe flavours.

The ideal is to have sugar ripeness and tannin ripeness at the same time. We would argue that this is one of the criteria of a great terroir. We would even question whether places that find this impossible, at least in the majority of years, can be considered great terroirs. To have sugar ripeness hugely out of sync with tannin ripeness makes it impossible to have balanced wines without regular intervention in the winery, whether it’s to add acidity or to add sugar. Is this too demanding an approach? Since it would rule out most of Western Europe at least until the 1980s, and much of the New World now, it perhaps is. But if were are talking about a great terroir – no, it’s not too demanding. And whereas until the 1980s the wine world’s problems were mostly about trying to make up for lack of ripeness, climate change means that an increasing number of our problems nowadays are to do with overripeness and loss of any ‘typical’ flavours from a vineyard. Grapes will have to be grown differently, and, if necessary, different varieties will need to be planted, ones which can express their sense of place in our warmer world. However you look at it, climate is an integral part of terroir.

Picking grapes too early can be unavoidable, if rain is on the way, or if, in cooler areas, a bad summer or autumn has meant that the grapes can’t ripen. In white grapes this means high levels of sharp-tasting malic acid; leaving the grapes on the vine for longer would mean lower levels of malic acid, which falls as the grapes ripen, and higher levels of the riper-tasting tartaric acid.
In red grapes, there is the additional factor of tannins, which should be silky. Green tannins range from dry to bitter and unpleasant, but a touch of greenness in flavour can add some balancing freshness without being in the least frightening; most great Bordeaux of the 20th century had a streak of greenness in them.

Some producers, however, particularly in California’s Napa Valley, but also in various other New World areas as well as parts of Spain and Italy and even in patches of Bordeaux itself, dread the thought of green tannins so much that they are apt to leave the grapes on the vine until they are shrivelled and are heading for raisin status. By this time sugar levels are sky-high and acidity is falling faster than stock markets after a Euro crisis. The wines may have tannins so soft you could wrap a baby in them, or they may have just got fiercer and fiercer, but either way, the wines have lost most of the freshness that makes you want to drink them.

And as for the alcohol, well, either it’s very high, or has been reduced from ‘very high’ by perfectly legal but hardly desirable methods involving dilution or manipulation of the grape juice or wine. It is perfectly possible to produce ripe, silky tannins without destroying the wine’s freshness, but you need the magic combination of a good ripening season in a relatively cool climate that will hold the sugar level back and prevent the grapes shrivelling to raisins while you wait for the tannins to ripen. Bordeaux at its finest is the best example of this.