What had happened was that the temperatures went too low in the winter for the yeast to finish consuming all the sugar. It had just gone dormant. Without the technology to test the amount of sugar remaining in a barrel of wine, the winemakers were at the mercy of the seasons and their intuition. When the warmer temperatures returned in the spring, the process of yeast fermentation just picked back up again. Winemakers today refer to this as a “secondary fermentation.”
