Back sweetening is the process used to turn a completely dry wine into either an off dry or sweet wine. This is just one of many ways in which you can produce a sweet wine.

The most common ways of back sweetening are by adding sugar or unfermented grape juice to a finished wine. By finished I mean fermented and stabilized.

Back Sweetening with Sugar

Often amateur winemakers will add sugar to a fully fermented dry wine to create a sweet wine. While this does work there are issues with the flavors of the wine and sugar.

Because the sugar was not a product of the grape and because it is added after the wine has finished fermenting it doesn’t completely integrate into the flavor profile of the wine. Instead you’ll have a sweet wine where you can actually taste the table sugar.

Aging a back sweetened wine can help integrate the flavor of the wine and the sugar. However, this has its limits. There are many out there that can pick out the table sugar flavors of wines sweetened this way.

Should you want to experiment with this method try it with a single glass of wine at first. Draw a sample glass of wine with a wine thief. Next, add table sugar in very small increments, tasting between each addition.

If you like what you taste then proceed to sweeten your entire batch. If not, consider leaving your wine dry.

Back Sweetening with Unfermented Grape Juice

Back sweetening wine is the process of adding unfermented sugars to a finished wine to make it sweeter.A more preferable method of back sweetening is to ferment the wine completely dry and add unfermented grape juice to it. This process is known as back-blending.

It works best when the juice used to sweeten the wine has come from the same juice that was fermented to make the wine. This makes for a much more integrated final product.

If you know you want to make a sweet wine from the start reserve a portion of the grape juice for sweetening. After the wine is dry and stable you can blend the unfermented juice back into your wine until it reaches the desired level of sweetness.

When back-blending add the unfermented grape juice in small amounts and taste samples often. It’s a good idea to first try this with a sample glass of wine. After all, you can’t un-sweeten a wine that is too sweet so be careful not to go to far.

Sweet wine kits come with a package of unfermented grape juice pre-measured in the correct proportions for the amount of wine made in the kit. The Riesling kit I made included an “F-Pack” of unfermented grape juice concentrate.

I can say from experience that the f-pack did not negatively affect the flavor profile of the wine. It tastes just as integrated today as it did before I back-blended it.

This is the preferable way to produce a sweet wine at the amateur level. Wineries have more complex methods, however, some wineries do produce sweet table wines by back-blending.

Stability is Key

The most important concern with back sweetening and back-blending is ensuring your wine is stable enough to reintroduce sugar to the mix. Sugar, after all, was the main food source that the yeast fed off of to create the wine to begin with so you’ve got to be sure fermentation won’t begin again if additional sugar is added.

Stability can be ensured through the use of additives or by filtering your wine. Additives such as potassium metabisulfite and potassium sorbate, when used together can prevent further fermentation of the added sugars. Potassium sorbate has its own issues though (read more here).

These additives only work with a completely dry wine though. You can’t stop a fermentation mid stream with these additives. In fact there are no additives for stopping a fermentation because they would be so harsh the wine wouldn’t be consumable afterward.

Filtering is an alternative that allows you to use less additives to ensure stability. While you will still want some sulfites in your wine you will be relying mainly on the filter to remove all the still living yeast cells.

Stop and think about that for a second though. Be filtering you are passing your wine through a medium so fine it can remove single cell organisms suspended in the wine.

A filter this fine is also fine enough to remove flavor, aroma, and color compounds from your wine. Many winemakers don’t like filtering for this reason. It removes character in addition to the yeast.

Photo used under creative common license. Taken by: Gabriele Cantini

  • I’m going to give this a try with some concord grape wine I made. I picked up some concentrated grape juice at the store that I am going to use.

  • OK, I did it – I stabilized, and after 2 weeks with no visible fermentation, back sweetened with sugar (we both liked the taste of the sample). Bottled, set aside for aging. 1 week later my bottles are popping their corks. Uncork the remaining 25 bottles and back into the carboy.
    My question is, what do I do now? If I can’t stop the rekindled ferment, what am I going to end up with? Brandy? This batch is a mix of Braeburn Apples and fresh cranberries.

    • I’m very sorry to hear that your wine started fermenting again. It can certainly be challenging to get the stabilizer just right so this doesn’t happen. I’ve done the same thing.

      Unfortunately the only way to safely stop a fermentation is to filter it with a sterile filter pad. These will remove the yeast from your wine. Otherwise you’ll have to let it ferment out.

      Depending on the alcohol and sugar levels you’re dealing with there’s a possibility that the alcohol will get too high for the yeast before all the sugar is used up. Then you would be left with a stable and sweet wine albeit high in alcohol.

      If you used a yeast strain that has a high alcohol tolerance then there’s a chance that you could wind up with a high alcohol dry wine.

      I wish I could offer you a more conclusive guess as to how this will turn out but as you can see there are quite a few factors at play here.

      • Thanks Matt. Airlock still bubbling, so we’ll see. I think I’ll abandon the back sweeting for now – at least until I pick a few more experienced brains on the subject. My dry wines have turned out awesome.

        • Back sweetening can be a bit of a trick. I’ve made the mistake of forgetting the sorbate and wound up re-starting fermentation. If you’re looking for some experienced minds to pick you’re welcome to join the Winemaker’s Academy Facebook Group. Just send me an email and I’ll get you an invitation to join. We’ve got almost 450 winemakers you can talk to in there.

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  • bruce

    do I stabilize and back sweeten in the same step?

    • Hi bruce, typically you would stabilize with potassium sorbate and potassium metabisulfite, then back sweeten to taste, then bottle. Even though the wine has been stabilized it is not recommended that you leave it in a carboy. It’s best to get it under the protection of a cork or alternative closure.

  • Hi David, back sweetening should be done to suit your taste. I’ve never come across a formula for predicting the amount of sweetener you would need. The best thing to do is bench trials. Measure out a few samples of wine, say 100ml, add some sweetener (juice in your case) in a measured amount, then when you find the mix you like replicate the same ratio when you back sweeten the rest of your wine.