The term “vinegar” comes from the French vin aigre, or sour wine. It is also used to describe other soured, alcohol-based liquids, such as those made from cider, malt or rice wine. Souring is a natural process that occurs when a liquid containing less than 18 percent alcohol is exposed to the air. Bacteria present in the air react with the alcohol to produce a thick, moldy looking skin over the surface of the liquid, which is called the “mother.” In simple scientific terms, the mother is a layer of yeast cells and bacteria that converts the alcohol into a natural acetic acid, and it is this acid that gives vinegar its characteristic sharpness.

Although this reaction does occur naturally, it is not always consistent. To produce quality vinegars, the speed and temperature of this process must be controlled. This explains why it is not enough to leave an open bottle of wine or ale on the kitchen counter for a few days and expect it to turn into vinegar. If unmonitored, the souring process can result in loss of flavor, or in further bacterial action and the production of unpleasant bitter flavors. In the kitchen, wine vinegars are indispensable for salad dressings, marinades and deglazing. Rice wine vinegar is vital for flavoring the rice in sushi, and malt vinegar is used in many pickles and, of course, on authentic, British-style fish and chips.

Types of Vinegar

In general, wine vinegars are required to have at least 6 percent acetic acid, while other vinegars range between 4 and 6 percent. Slight variations in acidity levels are barely perceptible on the palate; they need be of concern only when preparing pickles or other preserves.

Wine, malt and cider vinegar are strong, but distilled and spirit vinegars are even stronger. While any vinegar can be distilled, malt vinegar is most often used for this process. The distillation concentrates the acetic acid, increasing the level above 6 percent.

The vinegar made in any given country tends to reflect the produce of the region. Winemaking countries, such as France, Italy and Spain, produce wine vinegars. Where apples are a main crop, as in parts of North America, cider vinegar represents the bulk of production. Beer-brewing countries, such as Britain, produce malt vinegar. In the Far East, where wine is made from rice, a mild variety of rice wine vinegar containing 2 to 4 percent acetic acid is most widely used.

Wine vinegar: This is produced from both red and white wines, and the quality of the vinegar depends greatly on the quality of the wine. The finest wine vinegars are made by the Orleans method, which allows wine to ferment slowly and naturally (at about 70°F; 21°C) in oak barrels until the mother forms on the surface. However, this method is lengthy and costly, and many manufacturers speed up the process by raising the temperature. This results in a less costly—but also an inferior quality— vinegar.

There are almost as many types of wine vinegar as there are wines. Cham­pagne vinegar has a pale color and delicate flavor, while Rioja vinegar has a deep red color and a full rich taste. Sherry vinegar, with its deep caramel color and well-rounded mellow flavor, is matured in wooden casks similar to those in which the sherry is made and can be expensive.

As winemaking develops in North America and Australia, new kinds of vinegars, such as those made from California Zinfandel grapes, are emerging. A wine vinegar that has gained recognition in cuisines around the world is aceto balsamico, or balsamic vinegar. Made in Modena in northern Italy, it is named for the Italian word for “balm” referring to the smooth, mellow character of this unique vinegar.

Balsamic vinegar is made from unfermented grape juice that is aged in wooden casks. The quality of the finished product depends a great deal on the type of wood used and the skill of the vinegar maker. The finest vinegars are aged for a minimum of 10 years; the maximum aging time can extend for many decades.

Balsamic vinegar production demands an artistry equal to the production of a great wine. In Modena, fine aged balsamic vinegar may be served as an after-dinner drink. Traditionally made balsamic vinegar can be costly, although an industrially made version does exist and is an acceptable substitute for the traditional kind in most recipes.

Cider vinegar: Apple pulp or cider can be made into cider vinegar following the same method used to produce wine vinegar. There are recipes that call specifically for cider vinegar, but it has a strong, sharp flavor and so should only be used where it complements the other ingredients.

Commercial cider vinegars, which are filtered, are a pale brown color. Home-produced versions can become cloudy, but this does not affect their taste or indicate an inferior quality. The flavor is not smooth and refined enough for most salad dressings, but it can be used successfully in fruit pickles.

Malt vinegar: Made from malted barley, this type is most often used as a pickling vinegar for onions and other vegetables. Malt vinegar has too strong a flavor for use in salad dressings, but is the perfect condiment for fish and chips.

Powerful distilled malt vinegar, which is colorless, is for pickling watery vegetables, such as cucumber, which are likely to dilute the vinegar. It is also used in the manufacture of sauces and chutneys and is sometimes colored with caramel to produce brown malt vinegar.

Spirit vinegar: The strongest of all vinegars, this is used almost exclusively for pickling. It differs from distilled vinegar in that it contains a small quantity of alcohol.

Rice vinegar: Most common in the cuisines of Asia, this type is made from soured and fermented rice wines. Japanese rice vinegars are mellow and mild, while vinegar from China is sharp and sometimes slightly sour.

Depending on the rice used, Chinese vinegars are red or white in color. Like vinegars in the West, rice vinegar is often flavored. Soy sauce and mirin, or sweet rice wine, can be added, along with spices and flavorings such as gingerroot, dried bonito flakes, chilies, sesame seeds, onions, horseradish and mustard. There is also available a black Chinese vinegar, which is obtained from wheat, sorghum and millet instead of rice.

Reference: Wikipedia listing on Vinegar.