At the very beginning one of the chief matters to be looked to is the selection of the time at which the grapes should be picked. The proper period is that when the interior of the grape contains its principal components, the sugar and the acids, in the right proportions. In the warmer districts the grapes are sometimes allowed to become too ripe. In such a case there would be an excess of sugar and a deficiency of acid, and a regular fermentation would be impossible. On the other hand, it will be remembered in the course of the remarks upon pruning that I quoted Mr. Francois de Castella to show what a mistaken idea it is to pick the grapes before they are thoroughly ripe in order to produce, as it is erroneously supposed, a lighter wine. It is of the greatest consequence, therefore, to choose that particular time for gathering the grapes when they contain the respective elements in their strictly proper proportions.
On the eventful day for the picking of the grapes the weather should be fine and bright, and in the warm districts they should be picked early in the morning and late in the afternoon, so that they are not too warm. The grapes should never be taken to the fermenting house when too heated; indeed, it would be better not to crush the grapes at all than to have them in such a state. As Signor Bragato observes, if they are too warm the fermentation will start with too high a temperature in the must, and very likely the result will be the formation of lactic and acetic germs. In Algiers and other warm regions the grapes picked in the day are left outside during the night; by this means the temperature of the must is lowered.
In the picking of the grapes the greatest care should be taken to discard the mouldy, dry, and dirty grapes, and leaf insect worms should likewise be got rid of. Once the gathering of the grapes is commenced it should be concluded as quickly as possible, and therefore a sufficient number of hands must be engaged for the purpose. For instance, with the Riesling, if the grapes are left on the vines on a hot day twenty-four hours after they arrive at perfection, the wine will not be nearly so good.