The must, as we have already seen, is the juice of the grape, which has been squeezed out by the grape-mill or from the wine-press. The murk, or pomace as it is called in America, on the contrary, is the mass of grape skins, stalks, etc., left behind in the press. A clear apprehension of these two terms is required in order that no confusion may arise. The fermenting-vat is the cask in which what is called the strong, stormy, or tumultuous fermentation takes place. The "cuvage" is the length of time the contents are left in the fermenting-vat.
The whole phenomena of fermentation are too complicated and profoundly scientific to be dealt with here. I shall do no more, therefore, than briefly refer to the behaviour of the must in the fermenting-vat. Fermentation sets in soon after the must is placed within the latter. The germs of vinous fermentation are contained in abundance in the air of the wine cellar, as well as being on the grapes themselves. M. Pasteur, who has contributed so much to a proper understanding of fermentation, has proved that the yeast fungi come from the external surface of the grapes, and are not derived from the interior. Hence it follows that the skins are to be well crashed before fermentation begins, to ensure proper action in the must.
The temperature of the must soon begins to rise, and the fermentative agencies break up its glucose into alcohol and carbonic acid gas. There is a bubbling and seething in the liquid during this action, which gradually subsides. The increase of temperature in the fermented fluid begins to abate; the skins and husks subside to the bottom of the vat; the liquid itself becomes slightly less turbid - and the first stage of wine-making is at an end.
A clearer insight into this important part of the process will perhaps be gained by noting some of the practices followed on the Continent, as regards the duration of the vattage. The length of time the various contents - whether they be the grape juice alone, or the grape juice together with the skins and stalks - remain within the fermenting-vat, varies greatly in different parts. In the Champagne country, the must is allowed to stand for twelve or eighteen hours, during which time a froth arises to the top and a sediment descends to the bottom. Without disturbing either of these, the precious liquid is carefully withdrawn into small barrels, and the fermentation is then allowed to proceed. This purification is one of the most important matters connected with the making of champagne.
The Medoc districts, in the Bordeaux territory, produce the finest of the clarets. The grapes are detached from the stalks, and subjected to pressure. The must is put into the fermenting-vat, to which is added the murk resulting from ' the pressing, and the stalks which were previously separated from the berries. The time necessary for vinification varies; in good years it is no longer than four or five days, and the future wine will then be at its best with regard to taste, delicacy, and softness.
In one case, that of the Red Hermitage wine of France, the grapes are unstalked and crashed before being placed in the vat. The contents of the latter are then stirred twice a day, and ultimately once a day. This is continued for about a month, and in one of the best vineyards for forty days. This long "cuvage" appears necessary from the fact that the large amount of sugar in the must is but slowly transformed into alcohol.
There is a curious incident which occurs in connection with the world-renowned wines of Burgundy, which is worth recording. As the fermentation proceeds, the murk, as in all similar fermentations, rises to the surface of the vat, and forms what is called the " hat," or chapeau. The fermentation proceeds till all is ready for the wine to be drawn. At this time the "hat" is so dense that it will bear the weight of two or three men. Each of them now begins working with one foot till he gets it through the crust, and the whole chapeau is eventually broken up and mixed with the wine.
But to return to our subject. As soon as the stormy or seething fermentation is over, the young wine is drawn off from the fermenting-vat into the maturing-cask, at which time it may be quite warm and turbid. In a cool cellar and with perfect quiet it gradually becomes clearer; it deposits on the bottom of the cask many of the substances it contains, and the fermentation becomes no longer visible. The time which this "slow fermentation" takes to occur will vary with the type of wine, with the nature of the must, and with the influence of the season. Speaking generally, it may be said to be from two to eight weeks after its entrance into the maturing-cask. The wine is considered to be ready for its first racking when it has become clear and transparent, and when its lees have subsided to the bottom of the cask.
In racking there is a withdrawal of the wine from the sediment which it casts down, and which is known as the lees. It is an important operation because irremediable damage is caused to wine by allowing it to remain in contact with the dregs. A knowledge of their composition is of great value, since it serves to explain their injurious influence. The lees deposited from vinous fermentation consist of mineral salts, tartaric acid, and organic matters. Of these the organic substances are the most to be dreaded, and for this reason, that they are very prone to rapid decomposition. They consist of yeast-cells, cells of other micro-organisms, of debris and minute particles of grape stalks and skins, and of other bodies, all readily liable to decompose.
All these various materials, therefore, are continually a source of peril, for the slightest thing may start action in them, which spreads throughout the wine and simply ruins it. By removing it from such undesirable company all these risks are avoided, and the best possible qualities of the wine are afforded the opportunity to develop. In the performance of racking definite changes take place in the wine, which are assuredly important. For it must be remembered that the newly fermented young wines contain an excess of carbonic acid gas; and this is rightly regarded as possessing great preservative properties, in that it prevents the dangerously spreading growth of the little micro-organisms and germs present in all new wine.
In the course of racking, however, a certain amount of the carbonic acid gas must be lost, and fresh oxygen is absorbed from the atmosphere. The oxygen is invaluable from the fact that it exerts a powerful chemical influence upon the wine; as a consequence fermentation is slightly renewed if there be any grape sugar remaining. At the same time the colour of the wine is also modified, and any rawness or harshness in its taste subsides. And, lastly, its quality is enormously increased by the development of those delicate and subtle ethers which have so much to do with the flavour and bouquet of all wines.
The operation of racking, consequently, is one of great importance, as it requires to be repeated from time to time. A copious deposit of lees generally takes place after the first racking, and a second one should speedily follow. During the first year young wines are often racked off as many as three times, but with the older wines once a year, at the beginning, of spring, may be sufficient. But it is precisely in matters of this kind that judgment and experience are so much needed. Now, it has been pointed out over and over again that it is solely by a correct treatment of Australian wines in. the cellar that we can hope to attain to excellence; in fact, the whole secret lies in this direction. And it is very much to be regretted, therefore, that cellar management and wine treatment have not yet been conceded their proper position, that of being the principal factors in the success of Australian wine. Amongst others, this very truth was pointed out by Mr. Pownall, to whom I have previously referred. In giving evidence before the Vegetable Products Commission of Victoria in August 1889, he observed : - "In "some of the cellars I have been horrified with the amount "of wine which I should describe as 'perished' and as "'perishing.' It is astounding. I can hardly express the "quantity. And very often the vine-grower is so ignorant "of his business that he shows one wine which is 'tart' "and 'sour,' and even praises it. I find those wines are "generally exceeding three years old, and I attribute it to "the lack of cellar knowledge and treatment, because in the "same cellar where I find large quantities of bad wine I "find this year's and last year's wine good, and promising "well; but if longer kept, and so treated, after a few years "it will be utterly useless."
It will only be by paying attention to all the details connected with the cellarage of Australian wines that the victory will be ours. I have said so before, and now say it again, that our Australian must is quite equal to, if not superior to, any in the world. But it is from that very time that the critical stage in the making of our wines begins. It behoves our vignerons, therefore, to concentrate their energies mainly upon that vastly important period which follows onwards from the very beginning of vinification.