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Sweet Winemaking: All You Ever Wanted To Know

Sweet Winemaking: All You Ever Wanted To Know


Finding someone who doesn’t fancy sweet wine is a hard thing to do. We honestly like to end up drinking sweet wines at the end of a dining experience. We are even willing to give up on the dessert and raise the sugar intake by drinking rather than eating…

But for some unknown reasons, if you ask someone what the main production methods to make sweet wines are, it looks like they aren’t fully aware of the wide range of possibilities winemakers have.

It would be a shame to say that you love the luscious Tokaji without being able to give an exhaustive and reliable explanation of its production method, wouldn’t it?

Well, we are here today to clarify everything for you. Hopefully, you won’t even need to think about it anymore when another wine enthusiast is keen to know it.

How To Make Sweet Wine

Most wines are fermented to dryness. This is to say, that the yeast consumes all the sugar present in the juice. But sweet wines contain unfermented sugar. This is the only thing that every style adopted to make sweet wine has in common. There is still unfermented sugar. But the method used to retain this residual sugar determines the quality (and of course the price) of the final product.

The majority of us might think that the only way to obtain sweet wines is to actually add sugar or RCGM (Rectified Concentrated Grape Must). People might be amazed to know that the best examples of sweet wines don’t involve adding sugar at all…

Let’s discover all together the possibilities winemakers have to make sweet wine!

Figure 1: A glass of sweet wine and its shadow (, 2020)

Stopping The Fermentation

In this case, the fermentation is stopped by winemakers. Yeasts can’t get the job done, and covert all the sugar into alcohol, because winemakers interrupt their action. This means that winemakers don’t add any sugar, but they keep the residual sugar that is naturally present on the grape juice.

This can be done is several ways:

  • By fortification: This occurs when the spirit is added to the fermenting juice. It’s well known, that yeasts can’t survive with an alcohol level higher than 16.4% abv. Some examples are the luscious Port wines that are made by adding a spirit called “Aguardante” (which by law can’t be higher than 77% abv) to the fermenting juice. Don’t get confused with fortified wines such as Sherry. In this case, fortification happens only after the process of fermentation naturally comes to an end.
  • By adding a high dose of Sulfur Dioxide (SO₂): Generally speaking, some SO₂ is naturally produced in fermentation. But some producers may decide to add a bit of it to increase the stability of the wine since it has antioxidant and antiseptic properties. However, Sulfur Dioxide is toxic to many strains of yeast and bacteria that can cause unwanted flavor in wines. The principal yeast involved in the alcoholic fermentation is able to tolerate a level of SO₂ that kill other species, but it will die with a higher dose of added Sulfur Dioxide.
  • By chilling the fermenting wine: Temperature has a different impact on the yeasts. At high temperatures (over 35°C) they die. Wheres with low temperatures (under 5°C) they stop working (but they are still there and alive…). This is why wines made according to this method must be filtered to remove the yeasts. It’s imperative that no yeast comes in contact with the wine after this or else the fermentation would resume. An example is the well-known Moscato d’Asti;
Figure 2: Panettone and Moscato d’Asti, a pairing of the Italian tradition (, 2019)

Adding A Sweetening Component

This is the case of many medium-sweet wines made mostly (but by no mean only) in Germany by the addition of unfermented grape juice, called “Süssreserve“. This is obtained by filtering the juice before fermentation starts or by dosing it with SO₂. Süssreserve is added to dry wines when they are ready to be bottled.

Another way to achieve the same outcome is by using RCGM. This is especially the case of high-volume inexpensive sweet wines.

Concentrating Grape Sugars

Needless to say, this is the best method to obtain luscious sweet wines. The best examples come from grapes that are extremely rich in sugar. There are several ways to achieve this result, all of which have one thing in common: to concentrate acids, sugar, and flavors at the same time.

It’s important to specify that for this category the alcoholic fermentation stops naturally when the yeasts have converted as much sugar as they can into alcohol.

Figure 3: A bunch of frozen grapes ready to be picked to obtain an outstanding icewine (, 2019)

These are the techniques used by expert winemakers all over the world:

  • Drying grapes after picking (aka “Passito”): Dry and warm autumn are the main conditions required to obtain these wines, apart from the fact that grapes must be healthy. Winemakers have to be extra careful to select grapes or berries that haven’t been affected by any rot or this would spread otherwise. Among others, the Italian Recioto wines are a great example of this method.
  • Drying grapes on the vine (aka “Passerillage” or “Late Harvest“): Once again, warm and dry autumns are needed for this to happen or grey rot can develop. Once grapes have reached full-sugar ripeness, they begin to dehydrate and turn to raisins on the vine. This process increases the sugar concentration in the juice.
  • Ice wines: The name may be misleading as people might think that these are wines obtained by freezing the grapes! However, the freezing process happens naturally for the best examples. These are a type of (very!) late-harvest made from grapes that were left to freeze naturally on the vines. It’s important to highlight that healthy grapes are required to make ice wines. Pure varietal character in the wines is what winemakers want to achieve. Due to climatic changes, these wines are becoming a rare treasure. Canada and Germany are the places we look when we want to drink ice wine.
  • Noble rot: Every wine lover is familiar with the great effect of the Botrytis cinerea (aka “grey rot“). This fungus can be both the best or the worst winemakers’ friend. In fact, under specific conditions, this rot will allow winemakers to produce these luscious wines. These conditions are humid misty morning and sunny dry afternoons. And of course, nothing could be possible without grapes that are very prone to rot (Sémillon, Chenin Blanc, Sauvignon Blanc, Riesling are just a few of them). Apart from Tokaji, the famous Sauternes are made in this way.
Figure 4: Grapes affected by the noble rot, Botrytis Cinerea (, 2017)


As you can see, sweet wine isn’t just sweet wine. There is a world to take into consideration when talking about it.

You finally know all the methods used to obtain sweet wines you are finally ready to jump to the next level. As Italians, we take the chance to bring to your attention our sweet treasures.

If you want to know everything about sweet Italian wines, don’t miss the chance to read our article “The Ultimate Guide To The Italian Sweet DOCGs“. You will realize that Italy isn’t just about the sparkling Moscato d’Asti.

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