Chaptalizing Wine

updated 01/12/2022

I was recently asked how to chaptalize a must* prior to fermentation. Chaptalization is adding sugar to a must that is low in sugar, to increase the sugar level to a desired level. It is a common practice in France and other parts of the world, and is a tool a home winemaker needs to adjust for grapes and fruit that are low in sugar.

This post explains how to determine the amount of sugar needed and how to add it.

Note that sugar levels can be measured on different scales. I am using the Specific Gravity (SG) scale, while other tutorials may use the Brix scale.

* “must” is what the fruit and/or juice is called prior to fermentation.

Alcohol by Volume

The amount of alcohol by volume (ABV) contributes to the mouthfeel and enjoyment of the wine. Especially in red wines, a low ABV may cause the wine to taste thin. At the same time, too high an ABV may make the wine taste “hot” and unpleasant, so a balance is needed. To complicate the matter, the other constituents in wine affect the overall mouthfeel, and people have different thresholds for tasting alcohol. There is not a single correct answer regarding the ABV.

In general, I prefer an initial SG that ranges between 1.080 and 1.110, which produces an ABV roughly between 10% and 14%. Wines with an ABV below 10% do not have as long a shelf life and may taste thin, while wines above 14% can be hot and depending on the yeast variety, may not ferment to completion.

I mention this as it gives a beginning winemaker an idea regarding what ABV to target.

Chaptalization

As stated above, chaptalization is adding sugar to a deficient must to raise the SG to a desired level. The simplest way to do this is to stir in common table sugar in small amounts in a thin stream until the sugar dissolves and is evenly distributed in the must.

A sugar syrup can be made, which will dissolve easier, but for the range of ABV that I target, the sugar dissolves well and I avoid an extra step. If making a higher ABV wine (above 14%) sugar syrup may be better.

The SG should be checked periodically during this process to ensure that too much sugar is not added. Also, checking the SG will help ensure the sugar is distributed evenly, as a specific amount of sugar should increase the SG by a set amount — if the SG is not close to the expected value, either the must has not been stirred enough OR the original SG checked was not accurate.

When working with fresh grapes and fruit, I stir the must well, then check the SG in 3 different spots. If the 3 readings are not close in value, I stir more. Different bunches of grapes in a batch, especially large batches, may have different sugar levels. Stirring well helps ensure the must is homogeneous.

How Much Sugar to Add?

For common table sugar, 1 pound is roughly equal to 2-1/4 cups, and 1 pound of sugar will increase the SG of 1 gallon of water from 1.000 to 1.045. If we divide both sides of the equation by 4.5, the result is that 1/2 cup sugar will increase the SG of 1 gallon water from 1.000 to 1.010.

The following table displays the approximate amount of sugar that will increase the SG of 1 gallon of must:

Amount of Sugar	Increase in SG
1/4 cup	0.005
1/2 cup	0.010
3/4 cup	0.015
1 cup	0.020
1-1/4 cups	0.025
1-1/2 cups	0.030
1-3/4 cups	0.035
2 cups	0.040
2-1/4 cups	0.045

For example, let’s say we have a must with a SG of 1.060, and we want to increase it to 1.085. The difference is 0.025.

Looking at the table, we want to add 1-1/4 cups sugar for each gallon of must, so for a 10 gallon batch 12-1/2 cups is suggested, which is about 5.5 pounds of sugar. I say suggested as sugar is a natural product and the above amounts are approximate.

I recommend stirring the must and adding the sugar, 1 cup at a time, in a thin stream. Stir well after each addition, and check the SG after 25% of the sugar has been added. In this example, I would check the SG after 3 cups have been added, then again after 6 cups.

For small batches, such as 1 gallon of must, reduce the size of each addition to 1/4 or 1/8 cup.

Use caution when adding sugar — it’s FAR easier to add more than to take some out. If the SG is increasing faster than expected, stir the must well and check the SG again. Also, it may be necessary to check the SG after each addition, and it may be necessary to reduce the size of each addition, e.g., 1/2 cup instead of 1 cup.

Once reaching the target SG — STOP. If this is less sugar than calculated, it’s fine. The goal is to increase the SG to achieve a target, not to add a set amount of sugar.

If you have doubts regarding the reading, stir well and check again.