Liz Warensky, age 13, of Rome, N.Y., for her question:
WHERE DO WE GET VEGETABLE OIL?
Vegetable oil is a fatty substance obtained from certain plants. The chief vegetable oils used in the United States are corn, cottonseed and soybean oil. People use vegetable oils in frying food and as salad oil. Most salad dressings use soybean oil. Olive and peanut oils are also vegetable oils that are used extensively. Most margarine and other solid shortenings are made from corn, cottonseed, palm, safflower or soybean oil. Candy manufacturers use cocoa butter, coconut oil and palm kernel oil.
Production of vegetable oils starts with their extraction from fruit or seeds. Many oils are simply squeezed out. Often processors use a powerful machine called a high pressure press to squeeze out coconut and palm oil and some cottonseed oil. Oils may also be squeezed out under low pressure in a process called cold pressing. This process, which does not heat the oil as does the high pressure method, results in a light colored, mild flavored product.
A process known as solvent extraction is sometimes used to remove the oil. In this process, the manufacturer soaks the fruit or seeds in a liquid called a solvent that dissolves oil. A mixture of plant material, solvent and oil results.
Machines then remove the plant material and evaporate the solvent to obtain the oil. Most soybean oil is produced by solvent extraction. Processors squeeze part of the oil from some sources, including corn, cottonseed and peanuts. They remove the remaining oil from the seeds with solvents.
Oils obtained by high pressure or solvent extraction are bleached, deodorized and purified to produce a high quality product. Cold pressed oils require no further processing. The high pressure method often results in a dark color and strong flavor for the oil.
Many nonfood products also contain vegetable oil. As an example, manufacturers make cosmetics, shampoos and soaps from coconut, palm and palm kernel oil. Some medicines contain cocoa butter or castor, olive or wheat germ oil. Many paints and varnishes include a drying oil, such as linseed, soybean or tung oil. Drying oils combine with oxygen from the air to form a tough coating. Most vegetable oils are liquids. But several, including cocoa butter, coconut oil and palm oil, are solids at temperatures below about 75 degrees Fahrenheit. Vegetable oils are often used in preparing low cholesterol meals.