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Wines, Analysis Of

The following remarks on this subject are drawn from the admirable South Kensington Museum Handbook on "Food," by Professor Church. "When the sugary juice of any fruit is left to itself for a time at a moderately warm temperature, the change known as fermentation occurs. This fermentation is generally brought about by the growth of a low form of vegetable life--an organised rerment. It consists of a splitting up of the sugar present in the liquid (or at least of a large part of it) into alcohol, which remains in the liquid, and carbonic acid gas, which escapes more or less completely. "Although the fermented juice of all fruits may be regarded as wine, yet the term is generally limited to the alcoholic liquor prepared from the grape. But we have in England at least two familiar native wines--perry or pear wine, and cider or apple wine. Other so-called British wines are usually made-up or compound liquors, into which a large quantity of cane or beet sugar has been introduced. They cannot be regarded as true wines, nor are they generally wholesome. "The analysis of grapes shows us that the chief ingredient in their juice is glucose, a kind of sugar. There is also some albuminoid matter and a little tartaric acid, chiefly in combination with potash; other minor ingredients also exist in grape-juice. The seeds of the grape contain the astringent substance, tannin, with some bitter principles, while in the skins not only does colouring matter exist, but also some flavouring matters and tannin. From these facts it will be clearly seen that very different qualities of wine may be made from the same quality of grape, according to the method of operating upon the fruit. The colour, the bouquet, or volatile flavour, the astringency, etc., of a wine may thus be varied according to the admission or exclusion of the characteristic ingredients of the skins and stones of the grapes. "The main difference between grape-juice and grape-wine is the substitution of the sugar in the former by the alcohol which is characteristic of the latter. But other changes occur in the fermentation and ripening of wine. Much of the acid tartrate of potash is deposited from the liquid on being kept, this deposit being called argol. Argol consists chiefly of the above-mentioned tartrate, but with it a little colouring matter and some tartrate of lime are always found. In the stronger but natural white wines small floating crystals of cream of tartar often occur; they are nearly pure acid tartrate of potash. A small quantity of free acetic acid is found in wines. When they become sour it is this acid to which the sourness is due; it is formed by the oxidation of some of the alcohol present, a change which occurs more readily in weak natural wines than in those which contain much alcohol. Another important characteristic of wines is the presence in small quantity of certain compounds called ethers. They are usually fragrant, oily liquids, of which traces are present in all wines. These ethers are compounds formed by the union of the ordinary alcohol or spirit of wine with some of the acids which are contained in the fermented liquor--at least, this is usually the case. Much, then, of the flavour and perfume of a wine is due to these ethers, some of which existed, ready-formed in the grape itself, while others were slowly formed in keeping the fermented liquor. Different varieties of grape yield differently-flavoured wines, but the alcoholic strength of a wine depends mainly upon the proportion of sugar in the grapes, and in the degree of completion to which the process of fermentation is carried. The same kind of grape gives a very different wine as to flavour and alcoholic strength in accordance with the climate in which it is grown, the season, and the soil. "The quantity of true or absolute alcohol in natural wines varies from 7 per cent. in some hocks, clarets, and other light wines, to 13 per cent. in many Greek and Hungarian vintages. When the quantity of absolute alcohol exceeds 13 or 13 1/2 per cent., it may usually be considered that the wine has received an addition of distilled spirit, or been fortified. Wines of delicate flavour will not bear fortifying, the alcohol added being usually derived from the fermentation of artificially-prepared grape sugar, and containing the coarsely-flavoured alcohol known as fusil oil. A fortified wine may contain a good deal of sugar, for the addition of spirit to a fermenting liquid checks, more or less completely, the further change of the sugar. "Wines under 26(deg) of proof spirit pay on importation a duty of 1s. a gallon; those over 26(deg) and under 42(deg) pay 2s. 6d. Large and increasing quantities of natural wines now come into this country. Even of Spanish wines so imported about one-half are of natural strength, while the average of all Spanish wines does not show much over 28 per cent. of proof-spirit--rather less than 14 per cent. of absolute alcohol. "The following table shows the quantities of alcohol, of fixed acids--calculated as tartaric acid--of acetic acid, of sugar, of ethers, and of mineral matter or ash, contained in fair average samples of eight different kinds of wines commonly consumed in Europe. One imperial pint of each of the following wines contains about:- Name of Wine. Alcohol (absolute). Tartaric and other Acids. Acetic Acid. Sugar. Ethers. Mineral Matter. oz. gr. gr. gr. oz. gr. gr. gr. Hock . . 1 219 39 18 none 4 16 Claret . . 1 306 31 18 0 9 6 18 Champagne . . 1 343 20 10 1 120 5 20 Burgundy . . 2 18 24 17 0 10 6 18 Carlowitz . . 2 35 36 19 none 5 16 Sherry . . 3 147 24 12 0 236 4 38 Madeira . . 3 218 26 18 0 175 5 33 Port . . 3 218 23 12 0 359 6 20 "The different wines made in this country from rhubarb stalks, gooseberries, currants, cowslips, elderberries, oranges, etc., contain oxalic, malic, and other acids, besides the tartaric acid, which is the chief acid of the grape. Now these acids are not thrown out of the liquor after fermentation, as is the case to a great extent with the wine from grapes. Thus sugar has to be added to mask the acidity of these liqueurs, and in consequence they are not so wholesome as the natural imported wines. But it must not be supposed that grapes are entirely free from all acids save tartaric, or that the analyses as above given represent every constituent of the wines we have included in the table. "The ethers of wines previously alluded to include a number of compounds not yet completely analysed or understood. Some of them, however, have been examined pretty fully, and even exactly imitated by chemical means. OEnanthate, butyrate, and acetate of ethyl are the names given to some of the best known of these ethers. These ethers enter into the composition of the artificial `oil of cognac' and various flavouring essences."