Friday, March 9, 2007
Sweet Wines (Part II)
To briefly recap Part I: in order to make a naturally sweet wine you must somehow keep the yeast for consuming all the available grape sugar, leaving a “residual” amount behind to give the wine a naturally sweet taste. One way to do this is to “fortify” the fermenting juice by adding enough alcohol to kill off the yeast before it can finish its job. This produces high-alcohol wines that are not true “table wines,” meaning they are not well suited for accompanying a meal but are better served as before-dinner aperitifs or after-dinner dessert drinks.
So, just how is a naturally sweet table wine, one low in alcohol yet still possessing residual sugar, made? The answer is to creatively control both yeast and grape sugar. In the case of the yeast, you pick a strain that is more sensitive to alcohol, meaning it is less tolerant and so dies off at lower alcohol levels. With regards to sugar, you somehow come up with grapes that have an exceptionally high sugar content, which in essence means a high ratio of sugar to water inside the grape. So, how do you achieve this?
There are basically four ways of going about it: 1) leave your grapes on the vine until the last possible minute so you can pick them at maximum ripeness; 2) have your grapes attacked by botrytis; 3) have your grapes freeze; or, 4) partially dry your grapes like raisins. The first three methods require that Mother Nature cooperate fully in your efforts, a thing She is not often prone to do, while the last method demands lots and lots of sunny days, which again are frequently hard to come by.
Method 1: This is the most common way to increase grape sugar, as winemakers anywhere in the world can choose to hold off picking until they feel their grapes are at there best. But it takes the right combination of grape variety, excellent weather, and plain old luck to pull it off. You have to have a breed of grape with super-ripeness potential. You also need perfect growing conditions. And you have to pray or hope no last minute thunderstorm, hailstorm, windstorm, freeze, bug or blight comes along and wipes out your crop. Obviously this method is not for the risk-averse, but then farming is not for the faint of heart. (We forget that winemakers are very often farmers.)
Wines produced using this method are called, naturally enough, “Late Harvest” wines. In French the term is vendange tardive, and in German Spaetlese. You will see these terms used on wine labels and in essence they promise concentrated flavor and complexity. However, not all Late Harvest wines are sweet. If a winemaker wishes, he or she can allow all the sugar to be converted to alcohol and so produce a dry wine. In such cases the alcohol level will be at or near the upper end of the scale for table wines, i.e., somewhere between 13% and 15%.
What determines if the wine will be sweet or dry is the variety of yeast the winemaker uses. For a dry wine he or she selects one that can go the full distance, one that will keep on doing its job even in a high-alcohol environment. For a sweet wine, a winemaker picks one that will give up the ghost before it has managed to consume all the available sugar.
Method 2: Botrytis cinerea, called in France “the noble rot,” is a mold fungus that under rare and ideal conditions attacks grapes. In order for this to happen botrytis spores must be present in the soil and air and the temperature and humidity have to be just right. This combination occurs in only a few places in the world, the most famous being the Sauternes region of France and parts of Germany. When attacked by botrytis, grapes turn moldy and shrivel up like raisins as the moisture and life are sucked out of them. They end up looking rotten and terrible (see picture above, left), not at all like grapes that produce stunningly delicious wines. But, by removing moisture, botrytis concentrates the sugar level and ensures the little juice that remains is very, very sweet.
Unfortunately botrytis does not do a neat, even job of it. Some berries are infected earlier or more severely than others, so the wine maker must pick the berries individually, rather than by the bunch, to ensure they are all at their peak of sugar content. To do this the pickers must make numerous passes through the vineyard over a protracted period of time. This is not only labor intensive, and thus expensive, but it increases the chances the vineyard will be hit by adverse weather or a disease that could destroy the crop. The Germans have a long but descriptive name for wines of this type. They are called Trokenbeerenauslese, or a dry-special-berry-selected wine. In the Alsace region of France they are known as Selection de Grains Nobles wines. By any name they are extraordinarily delicious.
The outcome of all this work and risk is very little juice from which to make wine. Imagine squeezing raisins. Wines made from this juice are nectar-like, intensely sweet, yet with enough acid to keep them from being cloying. These wines are also rare and expensive, costing as much as $100 or more a half-bottle at the time of release. These wines will live a very long time and over the years will take on the color and taste of honey.
Method 3. Another way to achieve a high ratio of sugar to water in the juice is to freeze the grapes (above picture, right) and then crush them while they are partially frozen. Wine made this way is called “Ice Wine” (Eiswein in German). Of course the berries must be fully ripe, and in order to ensure this the winemaker must leave them on the vine deep into the growing season, which means into the early days of winter. In addition to praying that wind, hail, or disease doesn’t ruin the crop, the winemaker must also pray that when the grapes reach their ripest point Mother Nature will proved a perfect spell of freezing weather. You can imagine the odds of this happening. Like botrytised wines, Ice Wines are rare and expensive.
At one time Ice Wine was pretty much restricted to Germany, a kind of national specialty, but Canada now produces more than Germany does. The United States, and even Australia, also make it.
Method 4. The final method involves laying the grapes out in the sun, or placing them in a cool, airy room for months, and letting them dry up. It’s virtually the same process as that used to produce raisins, only you don’t let the grapes get quite as dry. In Italy this process is known as recioto and the best known wine made by this method is Recioto della Valpolicella, a sweet wine that tastes of cherries and plums, but with a slightly “cooked” or raisiny cast to it.
Ironically, it is not the sweet version of Recioto della Valpolicella that is best known, but the dry version called Amerone. This is a huge and powerful wine, meaning it’s not only a big, concentrated, mouth-filling wine, but carries the highest alcohol level of any table wine, often over 16%. It takes a very special strain of yeast to produce a wine like this. It’s worth noting that amaro is Italian for bitter, and Amerone does have a certain harshness to it, especially when young. It’s not everyone’s cup of tea, but if you ever come across one, it’s worth trying. If you have the time and patience to let it mature for 20 or 30 years, it can be quite wonderful. Amarone is not cheap, again because of the labor involved and the little juice that results.
I have not covered absolutely every means used to produce sweet wines, but the ones I’ve discussed are the main ones, the ones responsible for the most famous and best naturally sweet wines. In essence it’s simple. All you have to do is stop the yeast from consuming all the grape sugar. In practice, however, it involves a lot of hard work and luck. So, if you find yourself with a glass of Trokenbeerenauslese, a vintage Port, Eiswein, or a Grand Cru Sauternes, pause for a moment to reflect on what it is you’re holding in your hand. What you are about to enjoy is the end result of Mother Nature conspiring with human dedication to produce a miracle of taste.