Page:Popular Science Monthly Volume 26.djvu/389

Rh this purpose. This is a large metallic vat or boiler with air-tight cover and a false bottom, from which rises a trumpet-shaped tube through the middle of the vat, and passing through an air-tight fitting in the cover. The chamber formed by the false bottom is filled with water by means of this tube, the object being to prevent the wine at the lower part from being heated directly by the fire which is below the water-chamber. A thermometer is also inserted air-tight in the lid, with its bulb half-way down the vat. To allow for expansion a tube is similarly fitted into the lid. This is bent siphon-like, and its lower end dipped into a flask containing wine or water, so that air or vapor may escape and bubble through, but none enter. Even in drawing off from the Pasteuring vat into the cask the wine is not allowed to flow through the air, but is conveyed by a pipe which bends down, and dips to the bottom of the barrel.

If heated with exposure to air, the wine acquires a flavor easily recognized as the "goût de cuit," or flavor of cooking. By Pasteur's method, properly carried out, the only changes are those which would be otherwise produced by age.

These changes are somewhat obscure. One effect is probably that which more decidedly occurs in the maturing of whisky and other spirits distilled from grain—viz., the reduction of the proportion of amylic alcohol or fusel-oil, which, although less abundantly produced in the fermentation of grape-juice than in grain or potato spirit, is formed in varying quantities. Caproic alcohol and caprylic alcohol are also produced by the fermentation of grape-juice or the "marc" of grapes, i. e., the mixture of the whole juice and the skins. These are acrid, ill-flavored spirits, more conducive to headache than the ethylic alcohol, which is proper spirit of good wine. Every wine drinker knows that the amount of headache obtainable from a given quantity of wine, or a given outlay of cash, varies with the sample, and this variation appears to be due to these supplementary alcohols or ethers.

Another change appears to be the formation of ethers having choice flavors and bouquets; ænanthic ether, or the ether of wine, is the most important of these, and it is probably formed by the action of the natural acid salts of the wine upon its alcohol. Johnstone says: "So powerful is the odor of this substance, however, that few wines contain more than one forty-thousandth part of their bulk of it. Yet it is always present, can always be recognized by its smell, and is one of the general characteristics of all grape-wines." This ether is stated to be the basis of Hungarian wine-oil, which, according to the same authority, has been sold for flavoring brandy at the rate of sixty-nine dollars per pound. I am surprised that up to the present time it has not been cheaply produced in large quantities. Chemical problems that appear far more difficult have been practically solved.—Knowledge