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.
THE MAKING OF THE WINE—VARYING ADDITIONS TO THE MUST.
On the arrival of the grapes at the press-house, the first thing to be determined upon is whether the stalks are to be used or not. In the case of white wines it is not customary to separate them from the grapes. A good deal, however, will depend upon different circumstances. Thus, when grapes are grown in flat, damp places, or during wet seasons, it is often advantageous to ferment the berries with part of their stems; but, on the contrary, those grapes which contain a sufficiency of tannin will not require the latter. For example, in the production of white wines at Mr. Hans Irvine's ("Great Western") vineyard in Victoria, the grapes are first crushed with the mill, the mill consisting of two grooved wooden rollers working against each other. After this the skins, together with the stalks, are placed in the wine-press. In the case of red wine, however, the grapes are separated from the stalks by means of an iron griddle, so that only the skins are employed in the formation of the wine.
The methods pursued with regard to the elimination or retention of the grape stalks vary in different parts of the Continent. The most careful vignerons remove the stalks in the case of the finest growths of Burgundy; but in the making of champagne, and also in the Rheingau, from which part come the famous Hock wines, the stalks are allowed to remain. In the Medoc districts, which produce the finest clarets, the stalks are likewise put into the fermentation vat; but this is considered to be a great mistake, since a long time elapses before the astringent taste of the wine subsides. With the far-famed Red Hermitage wine of France, too, the stalks are permitted to pass into the vat, and in the case of sherry and port, as well, the stalks all take part in the fermentation, though it is believed that better results would be obtained by their removal. But in all these old wine-producing countries of Europe the same customs have been followed from time immemorial, and they are not likely to be altered at present.
THE MAKING OF THE WINE—THE MUST ITSELF.
The must—that is, the juice expressed from the grape, but in which (juice) fermentation has not yet taken place—is a fluid of very complex composition. It is made up of a variety of ingredients, with which it is necessary to become familiar in order to follow, during the process of fermentation, its change into wine. We find, therefore, that a large part of the must consists of water; this serves to dissolve the other constituents, and to dilute them to the required extent. For instance, the sugar in the must needs to be considerably diluted for the purposes of fermentation. In too concentrated a form it actually prevents it, as we see when fruits are preserved in syrup.
Next to water, sugar is the material which exists in the largest proportions in the must; it is, however, that peculiar kind of sugar termed "glucose," which may be described as uncrystallisable sugar, and as consisting of half grape sugar and half fruit sugar. It possesses the property of being able to ferment, which cane or crystallisable sugar cannot do, unless, indeed, it first be changed into glucose. Now, it is a curious fact that although cane sugar can be transformed into glucose, yet the latter form of sugar has never, so far, been changed into cane or crystallisable sugar. As Mr. J.A. Despeissis points out, the invention of a process that would achieve this would be worth more than all the mines of New South Wales put together.
In the process of fermentation the glucose is broken up into a number of substances, which differ entirely from it; and as these different bodies are very important they deserve much attention. Under the influence of fermentation glucose undergoes a great change, of which the principal products are alcohol and carbonic acid gas. The alcohol is, of course, the one predominant feature in wine; and according to the amount of alcohol which wine contains, so it varies in strength.
In addition to these two main products of glucose by fermentation, namely, alcohol and carbonic acid gas, there are glycerine and succinic acid, as well as a lesser proportion of other derivatives, very much akin to alcohol. Of all these glycerine is by no means unimportant, as it confers a blandness or mellowness upon the wine. The succinic acid, also, is distinctive for this reason, that it is the source of that characteristic flavour in wine known as "vinosity."