VINEGAR is a liquor containing the acetic acid obtained by the acetous fermentation or oxidation of alcoholic liquids— hard. cider, wine, beer, malt infusion, beet-root juice, fermenting molasses, dilute spirits or the like. Its color, varying from a pale yellow to a deep brownish red, and its odor and taste are influenced to a large extent by the materials employed in its manufacture. Vinegar obtained by acetous fermentation posses.ses different properties from pure acetic acid because it contains besides acetic acid and water— the essential constituents of vinegar — also small quantiues of substances, which being analogous to those occurring in wine may properly be termed bouquet bodies. These substances give the vinegar an. agreeable. odor and taste en urely lacking in synthetic vinegar prepared from commercial acetic acid. Even if an agreeable odor is obtained in the latter by 'the dition of certain volatile oils and compound ethers, the harmonious bouquet peculiar to vine gar obtained by acetous fermentation is never realized, the relation being homologous to that existing between artificial and genuine wine. Any one gifted with a delicate and practised sense of smell can at once distinguish acetic acid vinegar from wine, malt or fruit vinegar.
Vmegar obtained by the acetification of wine has been lcnown from the very earliest times, being used in this form contemporaneously with wine. Many noted scientists, such as Stahl, Davy, Berzelius, Naegeli, Liebig and Pasteur studied the process of acetous fermentation, and in 1822 Doebereiner suggested that acetifi cation is due to the action of oxygen on alcohol, which is converted into acetic add and water; Liebig sought to clarify this theory, and main tained that by the exposure, under suitable con ditions, of alcohol to the action of oxygen one third of the entire hydrogen contained is with drawn and aldehyde formed, which latter, how ever, immediately combines further with oxygen and is converted into acetic acid; the forma tion of vinegar from alcohol, therefore, being.a partial process of combustion. Acetification is, however, a far more complicated process than Liebig supposed and later investigations have shown it to be a chemico-physiological process with the co-operation of a living vegetable or ganism. It has been shown by Buchner and Weissenheimer that the acetous fermentation is due to enzymas existing in the plant cell. The presence of alcohol and oxygen alone will not suffice for acetification, the presence of nitrogenous bodies and certair. mineral salts are absolutely necessary. Pasteur was the first to consider the formation of vinegar from alco hol as a peculiar process of fermentation, main taining that a certain organism which he termed Mycodertna aceti, the °vinegar ferment" or °vinegar yeast° (popularly known as °mother* of vinegar), consumes the alcohol, the nitrog enous substances and the salts; on the other hand Naegeli asserts that this organism rather decomposes the particles of the substance to be fermented into simpler compounds. 'This or
ganistn, of which there are several different kinds, consists of a single cell, its special char acteristic being its manner of reproduction, which is effected by a division of the cell into two and then a separation or splitting of both. The cells form chains, which at 104° F. readily gro.w into long threads (involution forms). It is interesting to note that this organism not only oxidizes alcohol into acetic acid, but will also oxidize the latter into carbonic acid and water, in case alcohol is laelcing. This is an important factor in storing vinegar, as if it is allowed to come in contact with air the strength of the vinegar is lessened, owing to the con stunption of acetic acid by the tertnent Vinegar may be made according to the old slow process or by the newer quick process. The principle embodied in the old process is to allow wine, which is unfit for consumption as such, beer, malt-infusion, etc., to oxidize and to draw off the vinegar formed. We may say that this slow process is an adaptation of the spontaneous souring of beer, wine or fermented liquors in general but under such conditions as tend toward an improvement of the product While this process is employed especially for the preparation of wine vinegar it can neverthe less be used just as well for maldng malt or fruit vinegars. In this process old oak vats or casks are thoroughly cleansed with boiling water and saturated with strong boiling vine gar, whereupon the vats are filled two-thirds with the mixture of alcohol and vinegar. It is essential that the liquid contain no more than 14 per cent of alcohol, as the vinegar ferment per ishes in the presence ot more alcohol; a content of not less than 3 per cent of vinegar, while not absolutely necessary, is nevertheless bene ficial as it hastens the acetification. This alco holic liquid is technically termed the °wash.° The tempemture is maintained as nearly as possible at 76° F., and in a few days the acetous fermentation will have begun, which is then allowed to continue until completed, which re quires from 12 to 16 weeks. The vinegar is then drawn off and stored in a cool place in barrels which are filled to the bung hole and closed air-tight, in order to prevent the vinegar ferment from gaining oxygen from the air with which to oxidize the acetic acid and thus weaken the vinegar. Before storing, however, the vinegar is commonly passed through a °rape° or fining vat, having a layer of the residue calce from wine factories— the stems and skins of the pressed grapes. Through this it is passed again and again until every trace of alcohol has been oxidized. Another way is to *draw off the vinegar every weelc as it is formed and to add as much fresh °wash° as vinegar is drawn off. The process is practically continu ous and need only be interrupted after several years, when the accumulation of tartar and sedi ment renders a cleansing absolutely necessary.