Vinegar

Vinegar is made either by the microbial fermentation of alcohol or by the dilution of acetic acid. It has a pedigree probably spanning more than 10 000 years and, in that time, has been extensively used as food, medicine and for rituals. Wine being the first liquid to have spontaneously soured, we have the derivation of vinegar: Vin aigre - in French, sour wine.

Hippocrates understood the medicinal value of vinegar and such uses continued right through the Middle Ages and beyond as an internal and also topical treatment (remember Jack falling down the hill). The acidity represents formidable antimicrobial scope.

Vinegar is nowadays mostly used to afford desired acidic (sour) flavour to foodstuffs and to preserve them. It is still widely produced naturally ('brewed vinegars') by the oxidation of an alcoholic (less than 10-12% ABV) feedstock. The alcohol may be in the form of wine, cider, beer or other alcohol derived from the fermentation of grain, fruit, honey, potatoes, molasses or whey (Table 9.1). In industrial countries, more than 2L of vinegar are consumed per head each year. Apart from direct use in domestic cooking and in finished foods, it is used extensively inter alia for mayonnaises, sauces, ketchups and pickles. For pickling purposes, the acetic acid concentration should exceed 3.6% (w/v).

Table 9.1 Base materials for the production of vinegar.

Apple

Palm sap

Banana (and skins)

Peach

Cashew apples

Pear

Cocoa sweatings

Persimmon

Coconut water

Pineapple

Coffee pulp

Prickly pear

Dates

Prune

Ethanol

Rice

Honey

Sugar cane

Jackfruit

Sweet potato

Jamun

Tamarind

Kiwi fruit

Tea

Malted barley

Tomato

Mango

Watermelon

Maple products

Whey

Molasses

Wine

Orange

The key organism is Acetobacter (formerly known as Mycoderma), with pertinent strains being Acetobacter aceti, Acetobacter pastorianus and Acetobacter hansenii. Depending on the species, they function best in the temperature range 18-34° C. Fermentation is usually arrested when there is a minimal but finite residual ethanol presence so as to avoid over-oxidation to CO2 and water. The key equation is

The conversion of ethanol to acetic acid is accompanied by secondary fermentation important for the generation of aroma-active compounds, such as acetaldehyde, ethyl acetate and other esters, and higher alcohols, such as methyl butanol. The flavour so-derived (and also directly) depends on the source of the alcohol.

The Miracle Of Vinegar

The Miracle Of Vinegar

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