Vegetable oil is a fatty substance obtained from certain plants. In stores, products labeled as vegetable oil are typically made from soybeans. Soybean-based vegetable oil is an important ingredient in food preparation. It has a neutral flavor and does not readily break down under high heat. Canola oil, made from the seeds of the canola plant, has qualities similar to those of soybean oil and is used for the same purposes.
More broadly, vegetable oil can refer to any plant-based fat. Manufacturers obtain most vegetable oils from seeds and fruits. Oils made from corn, peanuts, and olives are widely used in cooking. These oils have stronger flavors than soybean and canola oil. Most vegetable oils are liquids. But a few, including cocoa butter, coconut oil, and palm oil, are solids at room temperature.
Uses.
Neutral-flavored vegetable oils are major ingredients in such foods as mayonnaise, margarine, and certain candies and baked goods. Cooks often use soybean and canola oil to brown foods quickly in a hot pan—a technique called sautéing. Peanut and corn oil are popular for deep-frying foods. Olive oil gives a distinctive fruity flavor to salad dressings, but its flavor breaks down during high heat cooking.
Many nonfood products also contain vegetable oils. For example, manufacturers make certain cosmetics and soaps from coconut or palm oil. Many paints and varnishes contain a drying oil, such as linseed, soybean, or tung oil. Drying oils combine with oxygen from the air to form a tough coating. See Oil (Fixed oils).
Production.
Manufacturers use various methods to extract oil from plants. One common process, called solvent extraction, involves soaking the seeds or fruit in a liquid known as a solvent. The solvent draws the oil out of the plant material. Machines then remove the plant material from the resulting mixture and evaporate the solvent, leaving only the oil.
Another method, called expeller pressing, uses a high-pressure press to squeeze out the oil. However, the high pressure heats the oil, causing it to develop a dark color and undesirable flavor. The oil also loses some of its nutritional value. A similar process, known as prepress solvent extraction, uses less pressure than does expeller pressing and extracts only some of the oil. A solvent is used to obtain the remaining oil.
Oils obtained by solvent extraction, expeller pressing, or prepress solvent extraction require further processing to make them suitable for use in foods. Machines refine, bleach, and deodorize the oils to create a clear, mild-tasting product. Oils obtained by a method called cold pressing do not require such processing. Cold pressing, which uses low pressure to squeeze out the oil, generates little heat. As a result, the oil retains its original flavor, color, and nutritional value. However, cold pressing removes less oil than do the other processes.
