Sweet Wine Chemistry + An Italian Granita Recipe
In Jeff’s Corner 8-25-15 I mentioned how much I enjoyed writing tasting notes for our new vintages because it forced me to take a closer look at our GCV sweet wines. Well, since then I’ve been sneaking around with our 2014 Riesling; meaning it’s been sneaking into my glass a lot after work.
So, with spring in full swing, let’s take a closer look at what’s going on with sweet wines. As we know, wine happens because of fermentation. Most wine grapes are harvested with a sugar content between 20 to 25%. Yeast is added to the grape juice and it converts the sugar into alcohol, and we have wine! A wine is considered “dry” when all the fermentable sugar is converted into alcohol.
The classic way to make a sweet wine is to stop fermentation prematurely and leave behind residual sugar from the juice; and the sooner we stop fermentation the more sugar we leave behind and the sweeter the wine. The residual sugar (RS) of my beloved GCV Riesling is 1.7%, and if we move the decimal to the right, we’ll have 17 grams of sugar in a liter.
Almost all the sugar in grape juice are equal parts fructose and glucose; these are the sugars that ferment into alcohol. There are, however, small amounts of unfermentable sugars (aribinose, xylose, and rhamnose) that will leave behind about .2% RS even when a wine is “dry”.
Now it gets tricky. Even though there are equal parts fructose and glucose, fructose is about twice as sweet as glucose. The yeast, however, ferments the less sweet glucose first, so even though we might have a wine with low RS, it is mostly the sweeter fructose.
A second way to make a sweet wine (besides stopping fermentation early) is to ferment dry, and then go back and add unfermented grape juice to a desired RS. If this is done, a wine at 1.7% RS will be less sweet then our 1.7% Riesling because of its higher percentage of glucose.
To confuse things a bit more, we all perceive sweetness differently. The average perceptible threshold is 1%, and most of our thresholds range between .5 and 2.5%. So, what appears very sweet to one person might seem much less so to another.
Whew, that’s enough chemistry and technical stuff! Let’s finish with a very simple, yet very elegant, spring and summer dessert made from our luscious Muscat Canelli.
An Italian Granita is a sweet and slushy frozen dessert made from fruit juice or wine. In France, it would be called a Granité. This is super simple. All you need is a bottle of Grape Creek Muscat Canelli and some fresh strawberries, raspberries, and blackberries.
1) Pour the wine into a sauté pan and simmer until the alcohol evaporates. This won’t take long, since it vaporizes at 168 degrees, long before the wine boils.
2) Freeze the wine overnight in a shallow, covered container.
3) Before serving, shave the ice with the tongs of a fork until it is a slushy consistency.
4) Cut the strawberries into pieces equal in size to the blackberries. Place the berries in the bottom of a frozen Martini glass and spoon the slush on top.
How easy is that! Besides berries, try fresh hill country peaches, watermelon, kiwi, or whatever fruit you like.
Thanks for reading, everyone, and we’ll see you next time!