Riesling Series Part I: Sweet vs. Dry Wines

In Part I of the Riesling Series, we’re going to talk about what it means for a wine to be sweet versus dry and how sweet wines are made. The first building block in understanding Riesling is nailing down the concept of ripeness of a grape so we will also explore that. Note: we are going to geek out a little bit in this post with some technical terms and definitions but having a basic understanding of these concepts is crucial in getting to know Riesling so bear with me!

Sweetness of a wine is often misunderstood. Fruit-forward and aromatic wines can sometimes be mischaracterized as being sweet, while they are nothing but bone dry. In order to start talking about why this is wrong, we first need to revisit a little chemistry: how do grapes turn into wine?

Fermentation is a chemical reaction that produces alcohol from grapes. There are differences in how white wine is made versus red wine, and many more nuances after that that differentiates one wine from another, but the overall process of fermentation begins after grapes are picked from the vine and get crushed. The natural sugars present in the grape get metabolized by yeast which produces alcohol (and carbon dioxide as a byproduct). So if all the yeast turns all the sugar into alcohol, the wine produced will be ‘dry’, with maximum possible alcohol content. If there is still some sugar left after all the yeast is used up, the alcohol produced will contain residual sugar, which will deem the wine as ‘sweet’ in varying degrees.

Let’s pause here for a second. If all the sugar is converted into alcohol, does that mean the wine will have higher alcohol? Yes! So, if not all sugar is converted into alcohol and there is a bit of residual sugar, does that mean the wine has lower alcohol? Yes! Does that mean sweeter the wine, lower the alcohol? Broadly speaking, yes! The point at which the winemaker decides to stop the fermentation is a very important. Sugar balances out acidity. If there is no residual sugar in a very acidic wine, the wine will not be enjoyable - take the sweetness out of coffee, soda or cocktails and no one would drink them.

Sweetness in a wine is a direct result of how much natural sugar there is in the grape. How much sugar there is in a grape is a direct result of: 1) How warm and sunny of a place the grape is growing in and 2) How long the winemaker waits before they decide to pick the grapes. The more abundant the sunshine and warmer the conditions, the more sugar there will be developing in a grape over time. The longer the grapes hang on the vine, the more time the grapes have to ripen and produce more sugar. There are a couple of more sweet winemaking techniques that we will discuss in the next post; don’t worry about those for now.

Dry wine doesn’t refer to an overly tannic wine that puckers your mouth. If you’ve been using the term ‘dry’ to describe that dry sensation in your mouth after drinking a Cabernet, you just learned that’s not true! On the flip side, sweet wine isn’t sweet because the winemaker stirs in a pound of sugar to the wine before its bottled*. The wine is sweet because the grapes either ripened in a warm place with lots of sunshine and the yeast couldn’t metabolize all the sugar, or because the winemaker decided to pick the grapes later than normal harvest time to allow the grapes to ripen beyond their usual potential, or a combination of these two things.

Now let’s talk about ripeness. All grapes begin their lives with lots of acid and very little sugar. As they ripen, acid content falls and sugar content increases. There are two kinds of ripeness: physiological ripeness (how developed the skin, stems, seeds are) and sugar ripeness. In this post, we’ll be focusing on sugar ripeness which is determined by the sugar content of the grape juice (technical term: must). As the grapes start to ripen, the winemaker will measure how much sugar there is in the grape juice periodically to determine when to pick the wines, using a device called the refractrometer. The sugar content in the grape is observed in units of Brix, Oechsle or KMW depending on the wine region. How many Brix of sugar there is in the grape juice will tell you what the alcohol potential is of the wine that you will produce. Simplified rule of thumb: 1 gram of sugar (1 Brix degree) fermented will result with about 0.5% alcohol.

Let’s go over an example. You’re growing Riesling in your vineyard and you want to make a dry wine. When your grapes start to show signs of ripening, you start measuring the sugar content every day. One day your refractometer device reads “20 Brix degrees” and you decide to harvest the wines. If all goes as planned during fermentation, and all the sugar is converted into alcohol, you will have a dry wine that has 11.5% ABV (alcohol by volume) on the bottle. If you had harvested when the must was 21 Brix, you’d have produced a dry wine with 12.2% ABV. Now lets imagine another scenario, where you are growing Riesling and want to make a sweet wine. You harvest when the refractometer reads 20 Brix again, but this time you stop fermentation after the yeast converts only a part of the sugar into alcohol so you have an 8% ABV wine. This means that the rest of the sugar content that was not converted into alcohol will determine how sweet your wine is.

Now that we know how a sweet wine is made, lets talk about how much sugar there actually is in wines and other beverages we consume daily.

In summary, the urban myth of sweet wines are for the ladies is absolutely not true. A winemaker chooses to leave sugar in the wine to balance out the acidity. The other incorrect myth is that sweet wines are lower quality wines. As we will explore later, some sweet wines are also the most expensive wines in the world with impeccable quality. Sweet wines have acquired a bad reputation, especially here in the US, because the bulk of the sweet wine that we find here is mass produced, lower quality wines. Throw these misconceptions out the door! Take Château d’Yquem as an example. d’Yquem has been producing sweet wines in the Sauternes region of Bordeaux for centuries. In 2011, a bottle of 1811 vintage d’Yquem sold for $117,000, a record number for white wines.

The German Trockenbeerenauslese Rieslings in a recent vintage can sell for upwards of tens of thousands of dollars. We will explore these (and all things Germany) in part II of the Riesling Series. Now that we know how sweet wine is made, we are fully equipped to handle the German Rieslings in all there glory. Stay tuned!

*There are exceptions to this: Chaptalization is the process of adding sugar to the must before fermentation. Colder wine regions can choose to add sugar to the harvested grapes to increase the alcohol potential. Not all wine regions allow chaptalization.