North316 wrote:The way I have always understood it is that they don't always have a choice. Consider the very basic fermenting process, sugar ferments into alcohol. The grapes develop their own sugar as they grow, which is dependent on the varietal, location, weather, harvest date etc. This sugar is then fermented and turned into alcohol. With that being said, dependent on the original sugar level in the fruit, if you want to stop the fermentation process at 13% alcohol, you could be left with some residual sugar, which would make the wine sweet, or sweet tasting. Obviously there are some things that can be done to reduce this sugar (ie harvesting at the right time) but it isn't always controllable. It's more about balance then an exact number.
The question is not so simple. The level of sugar in the grapes at harvest is usually expressed as degrees Brix. Assuming you ferment pretty much dry, the Brix level at harvest will pretty much determine the level of alcohol. So far so good.
But, how do you determine the optimum degree Brix at which to harvest? You're looking for something called 'phenolic ripeness' - the flavors you want in the grape to be transformed into wine. Many things affect this, rootstock, pruning, canopy management, weather, irrigation or dry farming, etc. And, different winemakers will want different flavors. The current demand for wines with very ripe flavors - plummy, jammy, etc. descriptors means that grapes will be riper than they need to be if you want 'fresh berry' flavors.
And, you definitely want to avoid underripe grapes, because they may not have enough sugar to properly ferment and you can't add sugar to the must in the US (chaptalization). In Europe, the grapes don't always ripen, so they strive to get riper grapes. Our problem in California is the opposite. It is rare that the grapes don't ripen enough before harvest (but it does happen - think 1972 and 1977).
30-40 years ago, when almost all vinifera vines in California were on St.George rootstock, and most winemakers were looking for fresh flavors in grapes rather than the much riper flavors many winemakers prefer today, and given the different canopy management, pruning and caning, and irrigation (or lack thereof) practices of the time, most people were able to achieve appropriate phenolic ripeness between 22.5 and 24 degrees Brix for red wines. At that level, there tends to be a better balance of acid (you tend to see lower pH values with lower alcohols and more tannins - those are the wines, if properly made, which can age for decades).
Over the past 30 years, there has been a move towards other rootstocks (including planting vinifera on its own rootstock), some of which turned out to be less resistant to phylloxera than thought which led to a renewed outbreak a decade or so ago (but I digress). There are reasons for the move away from St.George rootstock, including St.George's susceptibility to leaf roll virus. The result of all these things is that many winemakers say they cannot achieve phenolic ripeness at less than 25 degrees Brix or higher, which will take you close to 15% alcohol. A wine with 15.5% alcohol will have been harvested around 25.5 degrees Brix.
Thus, it has become common to harvest grapes well above 24 Brix - sometimes as high as 26-27 - for wines that are supposed to be dry table wines. Complicating this is the weather - if you have a heat spell shortly before harvest, sugars can rise quickly - so quickly that even if you were planning to harvest at 24 Brix you might have higher Brix by the time you actually got started and higher Brix yet (maybe a whole degree, even more) by the time you got all the grapes in. Worse, if you'd planned to harvest a lot later and the weather changes, you may have trouble getting your crews in early. Depends on how you're harvesting, how big and skilled your crews are. Planning for picking is as much a highly developed art as it is science, and Mother Nature can upset your plans easily.
Such wines will be very high in alcohol (unless alchohol reduction techniques are used) and low in acid (unless acid is added) and, however pleasant they may be as young wines, they will not have the balance necessary for the wines to age harmoniously.
And the foregoing is just scratching the surface....
Because I've been drinking wine a very long time, and my palate was first methodically developed in the '50s and '60s (by oenologist relatives whose palates were developed in Europe in the late 19th century and who knew the pre-phylloxera wines), and because I have been able to observe what does and does not age well over the past 50+ years, I am a strong proponent of fresher grape flavors (except in Port-style wines) and lower alcohols, with good tannin and acid balance. Those are the wines that will go 10 years and develop bottle age subtleties in most cases, and in exceptional years and from good producers will go anywhere from 20-40+ years. Good 1970 Cabernet (which came in at ~13.5%) is faded now, but still more interesting than almost anything made in the 'modern' Parkerized style in the past 25 years.
Even for daily drinkers, I look for wines that run under 14%, though one cannot be hard and fast about it when so much of the California production is north of 14%.