Chaptalization and Fermentation

Jean-Antoine Chaptal lacked one major benefit we enjoy today: The work in microbiology by Louis Pasteur. (Chaptal lived from 1756 to 1832 and Pasteur lived from 1822 to 1895.) Chaptal was, nonetheless, a brilliant chemist in his era and he introduced many improvements to industrial processes over the course of his lifetime. The one for which he is remembered among winemakers today is the addition of sugar to must in order to achieve a higher final alcohol in the wine. As a term, chaptalization is sometimes applied to the sweetening of a finished wine as well, but today’s article addresses it only for fermenting in must. So where does Pasteur come in? It happens that Chaptal reached a valid conclusion based on what we now consider faulty science. In the eighteenth century, wine was not very stable and spoilage was a serious concern that limited distribution and commerce. Chaptal observed that adding sugar to must, especially in cool regions or cold growing years, could produce wine that was more stable and aged better. His theory for this action postulated two