Vinegar is that form of Acetic Acid (q.v.) which is generally preferred for culinary purposes, and which is made by the fermentation of vegetable substances. In Great Britain it is manufactured on a large scale by the fermentation of malt; on the continent of Europe it is as largely made from low wines which have turned sour. Malt vinegar, or British, as it is sometimes called, is made by brewing a weak wort from malt exactly as for Beer (q.v.). To 100 gallons of this, at a temperature of 70° F., are added 4 gallons of yeast, and well stirred through for eight or ten minutes. This mixture is allowed to ferment actively for two days, and is then transferred to the stoving-room; here it is distributed into a number of tubs, which when filled are covered over with coarse canvas. This room is dark, and is heated by stoves, and the heat is constantly sustained for weeks until the conversion of the wort into vinegar is complete. The process of acetication is accelerated by introducing into the casks with the wort either the residuary fruit used in making domestic wine or the foot-stalks and skins of grapes. This rape, as it is called, acts as a kind of ferment. Various other processes are used by different manufacturers for the purpose of producing it quicker. Much vinegar is also made of beer which has become sour; it is, however, very inferior in quality. Vinegar prepared by these methods contains a large amount of foreign matters, which can be got rid of by simple distillation; the acid liquid which comes over constituting what is known in pharmacy as distilled vinegar. What is sold commercially as distilled vinegar is simply acetic acid distilled from wood (see PYROLIGNEOUS ACID), and diluted with five times its volume of water. This constitutes also the vinegar used by pickle manufacturers; it is quite as wholesome as common vinegar, but wants its agreeable flavour; its preservative powers are, however, much greater, and its price very much less. The addition of ammonia serves to distinguish French from English vinegar: with the former the colour is purplish; with the latter there is either no change or it is brownish.
As a condiment vinegar is an ingredient of a large number of sauces, and of ketchups and pickles; and although it cannot be regarded as an essential article of food, its applications in cookery are numberless. Young ladies with an undue tendency to corpulency are said sometimes to drink vinegar freely with the view of improving the figure; but, as vinegar only causes thinness by injuring the digestion, it is obviously not worth while to run the risk of exchanging slight fullness of habit for chronic dyspepsia.
Aromatic Vinegar consists of strong acetic acid, holding in solution camphor and the oils of cloves, lavender, rosemary, and lemons. It is very fragrant and volatile, and must be kept in well-stoppered bottles. It was formerly regarded as a valuable prophylactic of all infectious diseases, but is now only used as an external stimulant, the vapour being applied by a smelling-bottle to the nostrils in cases of fainting. See Acetic Acid and Vinegar (Technological Manuals, 1885), and W. T. Braunt's Manufacture of Vinegar (1889).