Fermentation Process

 The chemical process through which wine or fruit juice becomes vinegar involves the partial oxidation of ethyl alcohol that results in the formation of acetaldehyde, which is then converted into acetic acid (www.encyclopedia.com/topic/vinegar). The chemical reaction is as follows:

CH ₃ CH ₂ OH=2HCH ₃ CHO=CH ₃ COOH

Acetic acid bacteria are in the family Acetobacteraceae and Gluconobacter (Buchanan and Gibbons 1974). Acetic acid bacteria are Gram-negative, ellipsoidal to rod-shaped cells that have a need for aerobic metabolism as the terminal electron acceptor (Gonzalez et al., 2004).

The formation of vinegar starts with alcohol, with added sour ferment, all diluted with water and then exposed to the atmosphere. The vinegar becomes stronger the more alcohol that is present. The alcohol is the material in the vinegar mixture that the acetic acid is derived. The highest aim for the producer in the manufacture of vinegar is ultimately the conversion of alcohol into acetic acid with the least loss of alcohol possible (Francis & Croft, 1842).

Wine vinegar is prepared from wine and together with acetic acid contains all other constituents of wine such as tartaric acid. Cider vinegar is prepared from the fermented juice of apples and besides acetic acid contains malic acid which give apples their sour taste and is used in the food industry in fruit flavoured confectionary products. Malt vinegar is prepared from fermented extract of malt and as well as acetic acid contains nearly all the constituents of beer such as phosphates and extractive substances. Many of the substances which are used in the production of vinegar such as wine, fruit and malt contain the ingredients which ordinarily give rise to the formation of vinegar and they can be converted into vinegar sometimes without the addition of any acid ferment (Francis & Croft, 1842).