The SOMM Journal

August/September 2014

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{ SOMMjournal.com }  87 since the vast majority of table wines are fermented to dryness (this is true for more commercial styles, too, which often have a bit of sweetness that usually comes from a dollop of grape juice concentrate that is blended in to an otherwise dry wine). Another contributory factor is global warming. Well publi - cized studies by Dr. Gregory Jones at Oregon State University have shown, as people have suspected, that average growing season temperatures in wine regions worldwide have increased over the last 50 years. With these increases, vintage ratings have tended to increase as well, tying in with the notion that many consumers actually enjoy riper wine styles. A consequence of warmer wine regions is that harvests are often brought forward from autumn into the tail of summer, meaning that as harvest approaches, sugar levels can be rising fast. One factor that has led growers to pick later is a greater under - standing of the two different types of ripeness: sugar ripeness and phenolic (or physiological, or flavor) ripeness. While some viticulturalists don't like this simplistic separation, conceptually it is quite useful. Sugar ripeness refers to the way that sugar levels in grapes rise and acidity levels fall in a sort of tandem process. Phenolic ripeness refers to the way that the tannins in the grape skins soften, the green-tasting methoxypyrazines disappear and the seeds brown; during this process the grapes develop more flavor. In an ideal vineyard, in an ideal vintage, phenolic ripeness will be achieved with sugar levels that lead to an alcohol level of say 12 or 13% and acidity that is neither too high, nor too low (requiring supplementation). In many warm growing regions this simply never happens. Growers harvest when physiological ripeness is achieved, which can mean potential alcohol levels of 14.5 or 15% and acidity levels so low they need a hefty whack of tartaric acid to bring them back into line. Of course, there are different definitions of physiological ripeness. A trend that has been criticized in many quarters is for winegrowers to aim for super-ripeness, leaving the grapes to hang longer and longer. This results in what critics call "dead fruit" syndrome, as well as sky high alcohols and loss of freshness and definition. Praised by some critics, these wines are despised by others. One factor cited as a cause of rising alcohol levels is the increased efficiency of yeast strains in converting sugar into alcohol. However, it is not clear that this is really a contribut - ing factor because there is a low diversity in sugar-to-alcohol conversion factors among different strains of Saccharomyces cerevisiae. It would be interesting to see whether fermentation dynamics and the way that yeast populations develop could alter the efficiency of the fermentation process, but I am not aware of studies on this. How Alcohol Affects the Perception of Wine Is high alcohol a fault? This is a thorny question. If alcohol's only role in wine were as an intoxicant, then any perceived problem of high alcohol levels can be offset by user behavior: You just need to drink less! But this is clearly not the case. Alcohol has quite a profound impact on the flavor of wine. In considering whether high alcohol is a problem, it may be useful to think in terms of a hierarchy of faults in this context. Quality can be lost through alcohol levels that are too low as well as too high, because of the fact that alcohol changes the perception of wine. Consider Grenache, a grape variety that often has extremely high alcohol levels. If you are concerned about high alcohol and pick early, then you can end up with a boring wine with little flavor development. It may be that for your vineyard, Grenache shows best when you harvest it at a potential alcohol level of 15.5%. The negative effects of the high alcohol level are outweighed in this case by the benefits of proper flavor devel - opment, but the possibility remains that the wine might taste better at a lower level of alcohol. It's rare, perhaps unheard of, for a wine to be sent back in a restaurant because of over-high alcohol levels. In this sense, high alcohol isn't a fault. But it may be that many wines simply aren't enjoyed as much as they could be because the alcohol gets in the way. High alcohol is also a risk factor for other faults and wine - making problems. Alcohol is actually toxic to yeasts, and it also increases the toxicity of other compounds present in the fer- ment such as medium-chain-length fatty acids. High sugar musts can therefore create problems for winemakers by leading to stuck fermentations. Also, high alcohol red wines tend to be at higher risk of Brettanomyces because of the fact that there's often a little bit of residual sugar left at the end of fermenta - tion, and because they generally have higher levels of phenolic compounds—both of these can be used by brett as "food." A contributory factor to high alcohol is global warming. Average grow- ing season temperatures in wine regions worldwide have increased over the last 50 years. A consequence of warmer wine regions is that harvests are often brought forward from autumn into the tail of summer, meaning that as harvest approaches, sugar levels can be rising fast.

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