Last week we touched on soil considerations for new vineyards, thank you everyone Spencer Connell and Shelley Sharpe for your responses!
This week: Sweets
Name and describe various winemaking methods for achieving wines with residual sugar.
I start with one I'm currently studying: Mutage.
Mutage is a process to create vin doux naturel (sweet fortified wine) from all three colors of wine in which pure grape spirits are added during the fermentation process in a proportion of 5 to 10% to stop fermentation. This allows the wines to retain some natural grape sugar.
Riversaltes, in Roussillon, is the birthplace of vin doux naturel and the home of Arnaud de Villeneuve, a physician who introduced the process of mutage for medicinal purposes in the 13th century.
Residual sugar can also be achieved if the grapes have a high level of natural sugar. During fermentation, the yeasts may die from "alcohol poisoning" prior to converting all of the sugar (and thus leaving some behind) due to the high level of alcohol (around 16%) from the sugar that was converted.
Grapes can have high levels of natural sugar by/through:
1. being picked when sugar content is high (left on the vine longer to achieve extra ripeness);
2. laying them out on mats to dry out, which concentrates the sugars (think Amarone for example of part 1 and 2);
3. letting the grapes freeze on the vine such that water can be separated from sugar juice (icewine); and
4. Botrytis (noble rot) that consumes some of the water in the grape's pulp thereby concentrating the sugar.
I will add a method that is very much a part of my world—Icewine.
Eiswein is believed to have begun accidentally in Germany in the1700s when freezing weather hit before the harvest was in. Winemakers persisted and pressed the frozen grapes, ending up with a wine intensely sweet. The cold weather freezes the water in the grapes, and when pressed while frozen, the ice crystals are forced out resulting in intensely concentrated sugars.
In Canada, Icewine is a controlled term. Grapes must be registered with Vintners Quality Alliance (VQA) inspectors in November. They are netted and left on the vines until temperatures reach a sustainable -8C. Grape growers and winemakers watch for temperatures to reach -10C - -12C, an ideal temperature the sugars to reach 35 – 39 Brix. Because a sustained low temperature is required, harvest typically begins after sundown and usually takes place between December and February. Small hydraulic presses are used because much higher pressure is required. The expected yield per acre is about 500L, or 15% of the yield for a table wine.
Fermentation can be difficult in a juice with such high concentration of sugars, and the resulting wines are generally lower in alcohol. VQA requires at least 100g/L of residual sugar. The longer the grapes remain on the vine, the more dehydrated they become—creating beautifully complex flavours. If temperatures do not reach the required low before the grapes must be harvested, the resulting wine is labelled as a Late Harvest rather than an Icewine. Many varietals are used for Icewine, most commonly the Vidal hybrid, but Riesling and Cabernet Franc, and Gewurztraminer are frequently seen as well.
If you ever have a chance to participate in an Icewine harvest, do it. Many wineries rely on a small army of people willing to come at a moment’s notice to help, and some provide a large, celebratory dinner at the end of a long night of work.
If you are looking for an opportunity to taste a variety of Icewines with paired foods, go to the annual Niagara Icewine Festival in Ontario.