Also known as enrichment, chaptalization is a process in which the winemaker adds sugar to the must of grapes in order to increase the alcohol content.
Sugar and Alcohol in Fermentation
During fermentation, yeast interacts with the sugars in the grapes to produce alcohol and carbon dioxide. Once the sugar has been converted, alcohol content is maximized. Winemakers wishing to increase the alcohol level in their wine may add sugar to the grape must before fermentation, which gives the yeast more sugar to interact with, thus yielding a higher level of alcohol in the finished product.
The process of chaptalization works well with under-ripe grapes, as well as in poor climates and in areas where vineyards produce wines with low sugar content. High sugar grapes do not benefit from the addition of sugar to the must.
Most commonly, winemakers use cane sugar for chaptalization. Others use honey or beet sugar.
The Romans were the first to add sugar to grape must, although they didn't call the process chaptalization. Rather, they added honey to the must because they felt it improved the body and flavor of the wine without realizing that the process resulted in higher alcohol levels.
In the 18th century, French winemakers added sugar to the must, feeling it resulted in a sweeter wine; however, by mid century a chemist discovered that in truth adding sugar did not sweeten the wine. Rather, it increased the alcohol level and balanced the acidity present in wines made with low-sugar grapes. Soon, winemakers were adding sugar to preserve the wines.
Some countries allow chaptalization while others don't because they feel it floods the market with wines made from substandard fruit. Australia, Italy, California, and South Africa have all outlawed the practice. In the countries that do allow chaptalization, they limit total alcohol content to between 12 and 13.5 percent by volume.