The yeast is added and begin to convert, the sugar and must into alcohol and carbondioxide. Controlling the temperature of the ferment is imperative in white wine production. Keeping the temperature down ensures the flashed roll in primary characteristics of the grapes are maintained. Fermentation can be stopped by removing the yeast from the wine before it finished, converting all the sugar to alcohol. The remaining sugar is known as residual sugar. This is how wine makers manipulate the sweetness of white wine. The wine makers can also different yeast to create different flavours