Overripeness: one of the wine world's big issues 

Is overripeness a problem with many of today’s wine styles? In an earlier piece on this site I looked at the question of ripeness. This discussed the process of grape ripening: how grapes are for the birds, but contain natural antifeedant compounds such as bitter tannins and the green tasting methoxypyrazines to keep them away until the time is right. The vine wants to attract birds to spread grapes, but not too soon. Instead, it alerts birds to grapes by a colour change from green (hidden) to red/black (standing out) during a process that coincides with a reduction in green flavours, the development of sugar, the loss of acidity and changes in tannins so that the birds will do their dispersal job when the seeds are ready.

This is the familiar grape ripening process. Winemakers aren’t like birds though: they need to make a careful choice about when too pick if they want their wines to be of high quality. If they pick too soon, the acid levels will be too high, the sugars too low and the tannins too mean. If they pick too late, the sugar levels will be too high, the acids too low and the tannins will have evolved to a point where they don’t provide the wine with its required structure. In theory it sounds simple, but the devil is in the details.

The various chemical changes occurring during the ripening process take place in a complicated sequence, and are highly responsive to what’s going on in the environment. Traditionally, in the classic European regions judging peak ripeness was a rather simple issue. You picked the grapes when they reached a certain level of sugar, a measurement taken in the units Brix, Baume or Oeschle, depending where you came from. In these regions, where the summers have just enough heat to ripen the varieties that are planted in each location, the higher the sugar levels the better, because once the grapes have reached about 12 degrees potential alcohol, they’ll be ripe in all the other ways, too. Because of the constant threat of Autumn rains, it wouldn’t pay to leave the grapes on the vine much beyond this point: there’s a risk of severe quality loss if it starts bucketing down while the grapes remain unpicked.

As vines began to be planted widely in newer wine regions, commonly with warmer climates where an average summer has more than enough capacity to ripen the planted varieties, the rules suddenly changed a bit. Picking by sugar levels resulted in harvesting grapes that made wine with distinctive green characteristics and unresolved tannins: the grapes weren’t fully ripe. This new concept became dubbed ‘physiological’ or ‘phenolic’ ripeness (tannins are a group of phenolic compounds). In these warmer climates the process of sugar ripeness (with rising sugars and lowering acids) seemed to have become uncoupled from the process of physiological ripeness. So growers began leaving the grapes on the vines longer, leading to a concept dubbed ‘hang time’.

This extra hang time wasn’t such a risk in warmer climates, where the grapes were being harvested in weather more like a northern European summer than Autumn, and rain wasn’t a threat. This opened up possibilities to winemakers: picking became much more of a choice than in cooler European regions where winemakers had a lot less latitude to experiment. It also led to an unexpected problem: how should this new sort of ripeness be measured? Sugar measurements are trivial and can be made easily in the field. Measuring tannins and methoxypyrazines is a good deal trickier, so winemakers tend to rely on flavour for picking where sugar levels aren’t a good indicator of harvest time, alongside sugar and acid measurements.

Soon winemakers began toying with harvest dates, finding that the longer they left the grapes on the vine, the more some consumers and critics enjoyed the resulting wines. They became richer, with a sweeter fruit profile and softer tannins. They also became more concentrated and thicker, with darker colour. The alcohol levels became higher, mainly because of increased sugar levels but also because the grapes started dehydrating on the vine as they were left to hang.

Can you have too much of a good thing though? The pursuit of flavour or physiological ripeness has led to one of the biggest problems in wine today: ever-rising alcohol levels. Studies from Australia and California have shown that average alcohol levels have steadily been climbing over the last couple of decades such that it’s increasingly common to encounter wines that tip the scales at 14.5 or 15%. It’s barmy. Producers maintain that this is the price we have to pay for wines with the flavour profiles that consumers like: sweet fruit, soft tannins and lushness of texture. Some critics applaud these new wave wines; others complain that it has all gone too far.

‘Alcohol levels are a vexed question’, agrees Australian wine guru Brian Croser. ‘The biggest factor is the decision by most winemakers to pick later regardless of the physiological condition of the grapes. There are a lot of wines made from grapes past the use by date, shrivelled and physiologically dying or dead.’ Croser calls this phenomenon ‘dead grape syndrome’, and suggests that it ‘pertains to the best regions of the table wine world.’

'Viticultural practice has been revolutionised in the new world and sharpened up in the old world,’ continues Croser. ‘We now have very efficient solar panels in our vineyards (vertical canopies with good bud spacing, improved clones and rootstocks, good soil nutrition and water management) all leading to the highly desirable result of more rapid and complete ripening with more anabolic spill-over into flavour and colour and better retained acids.’

‘A bit like the cork/Stelvin issue there is an element of peer pressure, herd instinct, browbeating that bullies winemakers to avoid early picking despite the fact that our best vineyards are now set up to facilitate this by achieving early ripeness.’

I would hate to be a dictator of style, but I think it’s my job as a critic to give an opinion. And my view is that many of these high alcohol wines are suffering from overripeness because the grapes are simply being picked too late. I’m not advocating that producers pick grapes before they are ripe. And I’m not one of those critics who suggests that if a vineyard site produces wines with 15% alcohol that grapes should never have been planted there in the first place.

I think that for most vineyards and varieties, there is a window of picking when the grapes fall within acceptable parameters for ripeness, ranging from the cusp of greenness to the first signs of overripeness. Where the grower chooses to pick between these points is a stylistic issue. The current vogue is to go to the overripeness end of the spectrum, and in some cases beyond, and this is a mistake for three reasons.

First, the wines become boring, losing any sense of place that they might have had in the first place. It is increasingly common to encounter expensive, ambitious red wines in what is dubbed the ‘international’ style. They share the same sweet dark fruits flavour profile, with deep colour, soft tannins and lots of concentration. In an attempt to give them some bite and interest there’s usually a whack of spice from new oak. They are seductive and have an immediate appeal—they’re the sorts of wines that usually appeal to non-geeks—but they quickly become boring.

Second, the wines have too much alcohol. It’s not that I’m opposed to alcohol itself: Port is usually 20% alcohol and I like it a good deal. It’s just that in the context of a table wine, high alcohol has a profound effect on how the other components express themselves. The high alcohol is usually obvious on the nose, and it has an effect on the palate too, usually in terms of adding a little sweetness together with a bit of bitterness on the finish.

Third, and perhaps most importantly, I don’t think these wines age well. Of course, it’s not the destiny of all wine—not even all fine wine—to be cellared. But when we’re talking about expensive red wines, people are buying these with a view to future drinking, and are putting them in their cellars. Why don’t I think they will age? After all, Port ages well and that has 20% alcohol, as we have just mentioned, together with very sweet fruit. I think it has to do with the tannins.

Tannins are a complicated subject. They’re polymers made up of phenolic compounds, and have a marked astringent flavour. In both ripening grapes and wine, tannins undergo a range of modifications, including complexing with pigments, and increasing and decreasing in chain length. These chemical modifications change the sensory properties of the tannins, in ways that scientists are still busy working out: the simplistic view is that as they increase in length, they become less astringent, but the reality is more complex than that.

As we discussed earlier, one of the ways that grapes make themselves more tempting for birds is to become more palatable as they change colour from green to red, and one of these changes is that the tannins are modified on the vine to become less astringent. Part of red winemaking is to manage the extraction of tannins from the grape skins, and then help those tannins to rearrange in the right ways (for example, by the use of oxygen) such that the resulting wine has an appropriate structure; it follows that it is also important to pick the grapes at the right time so that the tannins are at the right stage. Pick too late, and the tannins will have already undergone lots of modification on the vine. The wine may taste soft and sweet, but there will be very little further room for the tannins to develop. If a winemaker intends to produce a vin de garde, then she or he will need to consider the state of the tannins, a decision that will impact on picking time and winemaking choices. Can you have your cake and eat it? Can you have a wine that is ripe and lush in its youth, and which has the requisite tannic structure? Only if there is actually some fairly serious tannin present that is masked by the sweetness of the fruit, as occurs with very good vintage Port. Or perhaps if the wine is very ripe but very heavily oaked, containing spicy oak tannins. Usually, though, I wouldn’t predict a good future for red wines that have been picked late and whose tannins have resolved on the vine.

Californian winemaker Randall Grahm has four suggestions for why grapes are being harvested at higher alcohol levels in new world regions, and suggests some remedial action where this is possible. First, daylight hours during the growing season, which depend on latitude. ‘Maybe this triggers some sort of hormonal process in the plant relative to its ripening pattern, and gives the Old World grapes a little goose to get on with it’, says Grahm. ‘Alas, nothing to be done in the New World short of a Dr Evil-like correction to the earth's rotational axis.’ Second, in many regions grapes are grown in regions warmer than needed to ripen the fruit, and with higher yields. ‘Growing grapes in cooler climates with restricted yields would certainly help bring the vines into better balance.’ Third, the use of drip irrigation produces shallow-rooted vines. Grahm thinks that dry farmed vines seem to be in just better balance: ‘they throw more appropriate crops and ripen them surely and evenly.’ Fourth, new world regions generally have bigger vines with larger carbohydrate reserves. ‘Perhaps it takes longer for the vine to get the hormonal message that it is time to stop growing and get on with the business of ripening its fruit,’ says Grahm.

Brian Croser also thinks that the size of the vine may have a role. ‘In high quality vineyards it is necessary to ensure the leaf to fruit ratio is adequate but not excessive. Many of the modern vertical canopy vineyards have much too much solar power for the crop load exacerbated by crop thinning. Nor does just raising the crop level to achieve the lower ratio achieve the right result. Small vines with small crop loads is the answer.’ He adds that, ‘You should ensure the daylight photosynthetic and net sugar accumulation time is matched by a night time anabolic phase ensuring optimum conversion of sugar to colour and flavour. Low day/night differentials, low vines receiving ground warmth all night is one way to go, another is to allow day time high temperature limit the photosynthetic duration and efficiency and to use the cooler but still physiologically appropriate temperatures at night to allow optimum anabolism.’

David Booth, a viticulturalist working in Portugal’s warm Alentejo region, also has some suggestions. ‘Soil water management is the main control’, he maintains. ‘I see well-managed deficit irrigation in the month preceding harvest like the joystick of a light aircraft, with the viticulturalist trying to put down the plane on a very short landing strip. A lot of high sugar levels in hot climates are not real sugar maturity but berry dehydration that produces an apparent rise in sugar level. We sample berry weight from a 500-berry sample every two days. This test is very good at detecting dehydration before you can actually see it appearing. We then do a very short, frequent, shallow irrigation just to keep the berries hydrated but without diluting them and keeping the vines in a state of moderate/severe water deficit so that they will have stomatal closure and no photosynthesis for most of the day. If we see the berry
weight go up, I ease off on the irrigation. All the time we are tasting and looking at seed, skin and pulp maturity and accurately measuring phenolic content so we have some numbers and can track the development of the curves on the graph.’ He gives the specific example of a wine that in 2004 had reached 13.7% potential alcohol by September 10th. ‘All the numbers on the phenolic tests were climbing nicely; aroma was beginning to build but still had some way to go, so we wanted to hold’, says Booth. ‘Using this irrigation technique I was able to hold the fruit at close to this level of sugar for nearly three weeks and we finally harvested at the end of September at 14.5%.’ He adds that, ‘I suspect that deep stony soils have a natural ability to place deep-rooted old vines under water deficit conditions then slowly meter in water. A skilfully managed irrigation system is trying to imitate this effect, just as modern
canopy management is trying to imitate the canopy environment of the old low
vigour vineyard.’

Still, there remains one further, and rather simple, solution: a stylistic decision that involves picking grapes earlier. It could well be that as well as making more complicated viticultural interventions to bring sugar levels down, a little compromise with early drinkability could result in wines that have more potential for ageing, and which are more interesting expressions of their site.

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