Wine Diseases

undesirable changes in the properties of wine caused by microorganisms. The causes of wine diseases were first experimentally established by the French microbiologist L. Pasteur in 1857. The commonest are the so-called wine mold, acetic fermentation (acetic oxidation) resulting from the activity of aerobic microorganisms, and lactic fermentation caused by bacteria capable of living without free access to air (facultative anaerobes).

The causative agents of wine mold are flors; the causative agents of acetic oxidation are acetobacters, which multiply on the surface of table wine having up to 14 percent alcohol by volume. They form a film on the wine that is exposed to air. Flors oxidize alcohol and organic acids, gradually converting wine into a liquid lacking in alcohol and acids and possessing a disagreeable odor and taste, whereas the acetobacters oxidize alcohol to acetic acid. To prevent wine mold and acetic fermentation, casks must be kept full at all times and cleanliness must be maintained during production.

Lactic fermentation is the most dangerous disease for all types of wine (dry and fortified). Preventive measures include maintenance of cleanliness during production, prompt separation of the wine from yeast lees, and acidification of low-acid wines. Sulfitation, pasteurization, and filtration by sterilization are used to destroy the causative agents of wine diseases. In addition to the above, other kinds of fermentation exist; there are also diseases causing wine to become oily and ropy and those causing wine to become bitter.