Wine is the result of a winemaker’s decisions with regards to viticulture and vinification. At the very least, he or she would need to ensure that grapes contain enough sugar for a successful alcoholic fermentation. Sugar alone however does not create quality wine. Grapes balancing all flavor components sought in a good wine are the starting point. Getting these is more difficult than it sounds, as overripeness can occur in days or even hours. Each grape variety also has its own tipping point, heavily influenced by the climate in which it is cultivated, adding to the constraints a winemaker faces.
There are numerous ways to make a sweet wine, but for today we’ll limit ourselves to those most commonly employed in Germany. The cheapest way is adding süssreserve (sterilized unfermented grape must) after the fermentation has run its course. I briefly mentioned the term when discussing Champagne, and I remain skeptical on its added value to quality wine. It is a drastic intervention in the wine that risks not adding anything but blandness, as we have learned from liebfraumilch.
Quality sweet wines are created through intervention in the alcoholic fermentation before all sugars have been converted into alcohol (thus the term residual sugar). The tricky part here is keeping a careful eye on three factors that will be key to a satisfactory result; alcohol, residual sugar and acidity. Monitoring for each of these during the process is not the issue, but keeping them in check, let alone divining how they influence each other as well as what the wine will end up tasting like is more easily said than done.
Acidity is really the one element that can make or break your wine. Too low, and you might as well be making syrup, too high and you end up with Fanta, sweet but too tart to taste it. When done right, though, you will have luscious, accentuated fruit shining through without leaving a hint of sugar on your tongue, just a long, lingering sensation. This, of course, requires that you use grapes with naturally high acidity, which is where the greats like Riesling or Chenin Blanc come into play.
I won’t send everyone running to the hills by attempting to explain German wine law and viticulture, but when it comes to sweet wines it can be handy to at least have a notion of what it all entails. Broadly speaking, Prädikat classifications are based on ‘degrees Oeschle’ an indicator of the ripeness of the grapes based on the must weight, which increases as sugars accumulate within the grape.
Over time these classification terms have become associated with sweet wines, but it is important to keep in mind that °Oeschle conveys info on the sugars present in the grape, not in the wine! With grapes that fall into Kabinett, Spätlese or in less frequent cases Auslese, a winemaker can simply decide to let the alcoholic fermentation run its course, ending up with 12 to 13% of alcohol. For instance, the VDP Pyramid (see Burgundian Riesling at Von Winning) requires Spätlese-level grapes for Grosses Gewachs wines, which are always dry.
The actual sweetness is up to the winemaker to decide. He or she can decide to halt the fermentation by adding sulfur dioxide or by lowering the temperature to a point where yeasts stop functioning (although in this case he would likely have to sterilize his wine in order to avoid refermentation in the bottle, which is a drastic move). The complication is that, unlike the Prädikat classifications, mentioning if a wine is trocken (dry), halbtrocken or feinherb (off-dry) is not legally required on the label, so sometimes you have no idea if the wine in front of you is sweet or not! The trick is to check the alcohol percentage. If this is in general higher than 11% in the case of spätlese and 13% for auslese, chances are you are in halbtrocken or trocken territory (dependent on where you are in the Oechsle range, but you get the general idea).
Starting from Auslese though, you will rarely encounter completely dry wines. Auslese grape picking commences in a stage of overripeness, comparable to the ‘vendange tardive’ as we know it in the Alsace. Beerenauslese goes even further, and whereas signs of noble rot can already be present in Auslese grapes, here we are already more on the level of ‘Sélection de Grains Nobles’ in the Alsace. Another apt comparison would be Coteaux de Layon versus Chaume and Quarts de Chaume in the Loire region where concentration and residual sugar potential are also considered as determinants of quality.
The Beerenauslese level will also see a steep increase in price. The stems become too weak to support the grape brunch, so yields plummet. Trockenbeerenauslese is even more exclusive, as only grapes fully infected with botrytis come in scope. It can be painstakingly difficult to make the selection in the vineyard as the right grapes have to be picked out one by one. These wines can be virtually indestructible, capable of aging for decades while retaining their thrilling balance between acidity and sweetness. I myself haven’t had a lot of occasions to taste them, and while I do recognize their quality they can be a bit too much on the syrupy side in their youth, especially if you are not used to drinking sweet wine.
Finally we get to Eiswein, a sweet wine that can really only be made in cold climates as you need frozen grapes. When temperatures hit -8°C, the water in the grape bunch will freeze, concentrating other components such as sugar and acids. Pressing must occur when the grapes are still frozen, so harvest is in general an all-nighter, resulting in a very pure, intensely sweet wine. The concentration of acids will preserve balance though and when done right, the wine can be extraordinary. °Oechsle would be in the same category as beerenauslese, but the key difference is that the best ice wines contain not a single trace of botrytis.
It is a risky business as a winemaker forgoes a part of the harvest in order to get a shot at making Eiswein, hoping for a decent winter. For instance, 2012 was the most recent year in which it was possible to produce Eiswein in large parts of Germany, but winter has not been strong enough in recent years, barring a few select locations. Yields are low at the harvest already and wild animals can ravage a vineyard still containing fruit. Winemakers may resort to using plastic coverage, although the downside is that it increases humidity, and thus the risk of botrytis.
As has hopefully become clear, there is a logic to the system, albeit a complicated one. We will take a look at a couple of young and old sweet wines over the next couple of weeks to show off the incredibly diversity riesling can offer with a bit more sugar!
photo credit – Peter Jakob Kuhn