Pre-Fermentation Treatments
Chaptalization
In the best terroirs of northern vineyards, unfavorable climatic conditions during difficult vintages often hinder maturation. Many parameters (reduced photosynthesis, continued vegetative growth, excessive crop yields, etc.) limit grape sugar accumulation; thus, adjusting the natural sugar concentration can be useful. Chaptalization is the process of adding sugar to unfermented grape must before or during fermentation in order to increase the alcohol content after fermentation.
Type of Sugar
Chaptalization has come to mean the use of beet sugar or cane sugar, both of which are composed of sucrose. In the manufacture of white wines, cane sugar is preferred to beet sugar, but for red wines the source of sugar is not so important. For white wines sugar should be added to the pressed juice, whereas in reds it is a must addition. The other sugar, which is becoming more widely used, comes from the grape itself and is composed of concentrated, unfermented grape juice.
Sugar Additions
The sugar should be dissolved before addition, because if added directly to the juice or must in a tank it falls to the bottom and forms a sweet layer as it slowly dissolves. To treat a tank, the required weight of sugar is added slowly into a small tank into which the juice or must is continuously mixed, and when dissolved completely it is pumped back into the larger fermentation tank. Sugar addition is best carried out in one step before or at the beginning of fermentation when the yeast is most active during the exponential phase of yeast growth (about 2�4 days after the commencement of fermentation).
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