Carrie Mattingly, age 11, of Watertown, N.Y., for her question:
HOW IS VINEGAR MADE?
Vinegar is a sour liquid that is used for seasoning foods and also for pickling and processing fruits, vegetables and meats. Vinegar is a result of the chemical change known as fermentation. A dilute or weak alcohol is the raw material from which all vinegar is made.
The name vinegar is from the French word "vinaigre," which means "sour wine." But many kinds of vinegar are not made from wine. The alcohol may be produced from the fermentation of the juice of any fruits, berries or even melons. Malt vinegar is made from cereals. Vinegar is also made from sugar solutions, such as molasses, sugar syrup or honey.
Cider vinegar is made from the juice of apples, or cider. Fermentation changes the fruit sugar into alcohol and carbonic gas. The gas evaporates, or passes off, leaving the alcohol and fruit flavors, or esters.
Oxidation changes cider into vinegar. The oxygen in the air comes in contact with the alcohol in the cider and with the aid of the vinegar bacteria, the alcohol changes into vinegar.
The two general methods of making vinegar are the slow, natural process and the quick process. The slow process may take from one or two years, depending on temperature and access to air. The fermented liquid may be kept in a special oak barrel with holes to permit air circulation. It should be only about four fifths full, so as to allow ample air space.
The alcohol, being lighter than the other part of the liquid, tends to rise to the top. As the alcohol comes in contact with air, acetic acid is formed. As the top layer turns to acetic acid, it gradually sinks to the bottom of the barrel. This process continues until almost all of the alcohol becomes vinegar.
In the quick method, the fermented cider is circulated continuously through vats called generators. The generators are filled with such porous material as corncobs or rattan shavings. Lukewarm cider is circulated through the porous material for 24 to 48 hours.
After 24 to 48 hours, the fermented cider is fed into the top of the generator through a revolving spray, or spanger. The cider is split into drops and each drop is brought into contact with currents of air that enter through holes near the bottom of the generator. An efficiently run generator converts 1,000 to 2,000 gallons of cider into vinegar in 48 to 72 hours.
During the process of converting fermented fruit juices into vinegar, particularly cider vinegar, a slimy scum called "mother of vinegar" (bacterium xylinum) forms. Manufacturers try to prevent the formation of vinegar mother. It slows down the circulation of air.
Odors of various kinds of vinegar come from the substances from which they are made. Cider vinegar has an apple like odor and is brown or yellow. Distilled vinegar is water white in color and has no flavor, other than acidity.
Most distilled vinegar is made from molasses. But some is made from whey, the liquid part of milk, which contains sugar. Four percent is the legal minimum acid strength for commercial vinegar.