Page:Encyclopædia Britannica, Ninth Edition, v. 24.djvu/641

Rh WINE 603 for exportation into Great Britain, are habitually doctored by the addition of cane sugar and cognac. Wine- Wine-Breiving. One mode of assisting nature in wine- brewing. m aking i s the process of &quot;gallisizing,&quot; so called from its inventor (Gall), which is largely practised on the Rhine. In a given vineyard the must produced in a good year is characterized by certain percentages of free acid and of sugar. In bad years the latter decreases and the former increases. But this, according to Gall, can be easily remedied by adding sugar and water in sufficient quantity to establish the percentages of free acid and sugar which are characteristic of the best years, and then allowing the mix ture to ferment. The sugar is added sometimes in the form of cane sugar (which is no doubt the best substitute for natural grape sugar obtainable), but more frequently in the form of what is known in commerce as &quot; grape sugar,&quot; which is in reality more or less impure dextrose produced from potatoes or maize starch (see SUGAR, vol. xxii. p. 623). Scientifically speaking, Gall s method appears to be un objectionable ; but that it does so is really owing to our ignorance of the intricacies of the actual process of grape- juice fermentation. In any case, grape juice is one thing and dextrose plus so much pump-water is another ; and the sale of gallisized as &quot;natural&quot; wine must be pro nounced a fraud. Science affords a means of distinguishing a gallisized from a natural wine, if the added sugar con sisted of dextrose. The sugar of normal grape juice is half dextrose and half laevulose ; a similar mixture is pro duced from added cane sugar. In the process of fermenta tion the dextrose is the first to disappear ; the rest of the laevulose then follows. Hence a finished natural wine, if it turns the plane of polarized light at all, will turn it to the left ; but, if the wine was doctored with dextrose, certain dextro-rotatory impurities survive to the end and the wine turns the plane of polarization to the right (Neubauer). A commission of experts who met in Berlin in 1884 declared gallisizing to be a legitimate practice as long as the water added does not amount to more than twice the weight of the added sugar. Liebig long ago recommended the addition of a concentrated solution of neutral tartrate of potash to ready-made wine, as a means for reducing its acidity. If the free acid is tartaric, it combines with the tartrate into cream of tartar, which gradually separates out and can be removed by decanta- tion or filtration. Long before Gall, Chaptal showed that bad must may be improved by adding the calculated weight of (cane) sugar and neutralizing the excessive acid by means of powdered marble. The principal feature in Chaptal s, as compared with Gall s method, is that it dis cards the resources of the pump. Plaster- In Spain, Portugal, and France it is a very common ing wine, practice to dust over the grapes with plaster of Paris or to add the plaster to the must. The intention is, in the former case, to prevent putrefaction of the berries, in the latter to add to the chemical stability of the wine. Ac cording to experience, a plastered wine is ready for bottling sooner than it would be in its natural condition. The chemical process involved consists in this : the sulphate of lime, CaSO 4, decomposes the bitartrate of potash, (C 4 H 4 O KH, of the must, with the formation of insoluble tartrate of lime, (C 4 H 4 O 6 )Ca, and soluble acid sulphate of potash, KHS0 4 . The latter takes up potash from, chiefly, the phosphate present and becomes normal salt, K 2 SO 4 , with the formation of free acid (e.g., phosphoric acid). A plastered wine is relatively rich in potash and in sulphuric acid. Amongst German wine-analysts it is customary to report all the sulphuric acid found as sulphate of potash, K 2 SO 4 . If the calculated sulphate amounts to less than 2 grammes per litre, the wine is passed as being at any rate not excessively plastered. But the interpretation of a sulphuric acid determination, in the case of German wines more especially, is rendered very uncertain owing to the widely spread practice that prevails of disinfecting wine- casks with sulphurous acid (by burning sulphur within them) before they are used. Want of space will not allow of the treatment of wine analysis generally; but sufficient has been said to show how far the genuineness of a wine can be proved by chemical analysis. Against the most important and fre quently occurring fraud, namely, the substitution of a genuine, but inferior, for a high class wine of a similar kind, chemical analysis is at present absolutely powerless. It sometimes happens that wine becomes viscous and Injurioui forms threads when poured from the bottle. This mischief, ferments which is caused by the development of a foreign ferment, &c can be cured by the judicious addition of a solution of tannin, which precipitates the &quot;gum.&quot; From a similar cause comes acetous fermentation, which always takes place in a moderate degree, but may assume undue dimensions. Red wines are liable to develop a foreign substance which imparts to them a bitter taste. A wine kept in a mouldy cask assumes of course a mouldy taste and smell. Some times a wine will &quot; capsize &quot; : the alcohol and the acid disappear and what was wine becomes an insipid un- drinkable liquid. Most of the injurious effects caused in wine by foreign ferments can be prevented by a process introduced by Pasteur. The wine is kept for a sufficient time at a temperature of 70 C. in the absence of air, and then transferred to a germ-free cask, without allowing it to come in contact with more air than can be helped. The only objection to Pasteur s precautionary method is that it renders the wine slightly flat through the removal of part of its carbonic acid. No doubt these deleterious con sequences might be prevented to a very great extent if the fermentation were conducted from the first in casks which communicated with the air only through a (wide enough) tube full of cotton wool, which medium is known to filter off all germs (see FERMENTATION, vol. ix. p. 95). E/ervescing or Sparkling Wines. These wines are Spark - largely impregnated with carbonic acid engendered by an lin s after-fermentation in the closed bottle by means of added W1 sugar. The art originated in Champagne, where the best sparkling wines are produced, and whence it has spread to the Rhine, the Moselle, and other districts. The natural wine of Champagne is not of a very high order ; yet it pro duces the best champagne. For champagne-making blue grapes are preferred. In eliminating the juice excessive pressure is avoided, so as to keep the must clear of particles of skin. The processes of fermentation and clearing, as well as those connected with the making of champagne generally, are described in detail below (p. 606). Cham pagne-makers distinguish three grades of effervescence. In mousseux the pressure in the bottle amounts to from 4 to 4 1 atmospheres; in grand mousseux it reaches 5 atmospheres ; and less than 4 atmospheres pressure con stitutes cremant (from la creme, &quot; cream &quot;), a wine which throws up a froth but does not give off carbonic acid violently. A champagne which contains relatively little sugar is called &quot;dry&quot;; it is chiefly this kind which is imported into Great Britain, where champagne is used habitually as a dinner wine. In France a sweet wine is preferred. The intensely sweet substance called &quot; saccha rine&quot; (see SUGAR, vol. xxii. p. 623) has been utilized for producing a sparkling wine which is both sweet and dry. Cheap champagnes may be (and we believe are) produced by simply adding sugar and some flavouring matter to wine, and then pumping in carbonic acid in the soda-water fashion. The following extract from a table by August Dupre will show the chemical composition of the wines most popular in Great Britain. The numbers may be