There are several ways to produce sweet wines and the method of production impacts greatly the quality and the cost of the production. The two classic production methods to attain a high level of residual sugar include sweetening and arresting fermentation (leaving unfermented residual sugar).
Sweetening is the least expensive and the least qualitative. The sugar can come from straight granulated sugar (from beet sugar or sugar cane), from concentrated grape juice (under the sexy acronym RCM standing for Rectified Concentrated Must) or it can come from the addition of unfermented grape juice (aka Sussreserve in Germany). None of those methods are very qualitative but they do the job of raising sugar levels rather cheaply. Sweetening is sometimes prohibited though often more for tax and volume control reasons rather than for quality considerations.
Arresting fermentation is the most qualitative method to keep a wine with residual sugar. The fermentation is stopped either by killing or removing the fermenting yeasts. Yeasts die because they are tired or because they are killed from either a purposeful combination of cold temperatures and sulfites or by fortification (the addition of alcohol – think Ports). Alternatively yeasts can be removed with a centrifuge. Centrifugation is the easiest technique though the equipment is expensive and some winemakers have concerns about putting their wines through what can sometimes be referred to as a “giant salad spinner.” We use a centrifuge for some of our higher volume wines for speed, accuracy and we tend to use a bit less sulfites that way. For wines that are not concentrated (more on those styles later), the level of residual sugar correlates well with the alcohol level. For example the Sweet Riesling is arrested at 65 g/L residual sugar and an attained alcohol level of 8.5%, versus our Riesling “J” that is arrested at 25 g/L residual sugar with 11.5% alcohol.
There is a special category of wines that are concentrated in sugar before they start fermenting and are then arrested. The concentration can be done through three processes: selective press fraction of frozen grapes (Ice Wine and other cryoextracted delights), dehydration (think Recioto, vin de paille) or the action of noble rot aka “good” botrytis (Sauternes, Tokaj Aszu for example). The concentration always reduces volumes which means the costs per gallon is much higher for the producer. Additionally most concentration techniques result in a high percentage of waste further adding to the cost. For example, a botrytized harvest can have a significant fraction of their crop wasted as they go sour instead of “noble,” similarly grapes left for Ice Wine do not always freeze and may be wasted ruining a full vintage. Only the cryoextraction method does not create waste – with this method, grapes are harvested when they are healthy and the freezing occurs in a warehouse. We make our Vin de Glaciere Riesling in this manner.
This brings me to our latest releases: the 2013 Riesling Ice Wine and the 2012 Noble Riesling. Both are were hand-harvested from Selenium Vineyard in the Yakima Valley and both are concentrated sweet wines, one by the action of Botrytis (the “noble” wine) and one by freezing on the vines (Ice Wine).
The 2013 Ice Wine is the latest frozen on the vine harvest we have made (the last time the weather allowed us to make this was in 2009). It is a special harvest for me because it was done on December 6th aka Saint Nicolas Day. It was a cold 8F that morning and the fruit was handpicked and pressed for 24 hours the same day. The resulting juice was 34 Brix and lead to about 117 cases of wine. The juice was fermented with R2 yeasts which is a selected yeast for high sugar environment and the fermentation was arrested by cooling the tank and adding sulfites at 155 g/L residual sugar and 9% acquired alcohol. Ice Wines like this one are always very pure and crystalline – especially if they are made, like this example, with the high acidity and focused Riesling grape. This is a glorious example of Ice Wine with the high residual sugar perfectly balanced by Riesling’s high acidity.
The 2012 Noble Riesling is a first for us and a happy accident. We do not always have good botrytis or enough botrytis in Eastern Washington to make a fully botrytized wine. We did get plenty of botrytis in 2011 which we picked in 2012 (February 8th for the record). First, don’t ask me why it has to be labeled as a 2012 when the grapes were grown in 2011 – go ask the federal government as it is their rule. Second, we waited that long to pick because we…. Mmmmm… forgot about that block and when I went to check the field pre-pruning I discovered a field full of perfectly botrytized berries waiting to be picked. To add to the serendipitous nature of this wine, it started to ferment on its own and, being always one for natural processes, we did let it ferment with native yeasts. Oh – it also stopped on its own at 170 g/L residual sugar. This free-spirit Noble Riesling is to put it plainly: the best wine we’ve ever made. It is concentrated, elegant and intense.
Making sweet concentrated styles with those methods is very rewarding though the quantities are always small. To highlight the small production, we have numbered and signed every bottle we made.
If you want to have fun explore the different ways we make a sweet wine I invite you to try a Sweet Riesling, a Vin de Glaciere (cryoextracted), the 2013 Selenium Vineyard Riesling Ice Wine and the 2012 Selenium Vineyard Noble Riesling. If you want a great gift idea to a dessert wine lover friend or even for yourself, consider a duo of the Noble and the Ice Wines – you won’t regret it.