Vegetable oil

Vegetable oils, also called vegetable fats, are substances extracted from the seeds or other parts of edible plants. Chemically, these fats are mixtures of triglycerides. While the term often refers to oils that remain liquid at room temperature, they can vary in consistency. Some examples include seed oils like soybean, canola, and grapeseed oil. Other examples include fats from different plant parts, such as olive oil, palm oil, and rice bran oil. In the United States, the Food and Drug Administration recognizes these oils as generally recognized as safe (GRAS).

To produce these oils, manufacturers use two primary methods: mechanical extraction and chemical extraction. Mechanical extraction, often called crushing or pressing, is used for traditional oils like coconut or olive oil. This involves physical force using tools like a screw press, a ram press, or a traditional Indian ghani, which is a powered mortar and pestle. Chemical extraction is more common for modern industrial oils like corn or soybean oil. This process uses a solvent, most often petroleum-derived hexane, to pull the oil from the plant material. After extraction, the mixture is heated to about 250 degrees Fahrenheit to evaporate the solvent. Some producers use supercritical carbon dioxide as a non-toxic alternative to chemical solvents.

Vegetable oils are categorized by the plant part they come from. Seed oils are derived from the seeds of plants and include cocoa butter and soybean oil. Other types come from different structures, such as the fruit or the plant itself. For example, olive oil and palm oil are distinct from seed-based oils. Some oils can also undergo a chemical process called hydrogenation. In this process, liquid fats are treated with a metal catalyst, like nickel, in a near-vacuum at high temperatures. This introduces hydrogen and breaks double bonds between carbon atoms. This transformation can create solid fats, such as margarine or vegetable shortening.

Humanity has utilized plant oils for thousands of years. Archaeological evidence shows that olives were being processed into oil in present-day Israel as early as 6000 BC and 4500 BC. In ancient Egypt, plant oils like cedar and cypress were used during the mummification process. During the Industrial Revolution, British traders used palm oil as an industrial lubricant for machinery. By 1870, palm oil was a primary export for several West African countries. In the early 20th century, the science of fats advanced significantly. In 1780, Carl Wilhelm Scheele showed that fats come from glycerol. Later, Michel Eugène Chevreul deduced that these fats are esters of fatty acids and glycerol.

Global production of vegetable oil is massive and growing. Between 2000 and 2020, production increased by 125%, largely due to palm oil. In the 2018–2019 period, world production reached 57.4 million metric tons (MT). China was the leading producer with 16.6 MT, followed by the United States with 10.9 MT. Argentina produced 8.4 MT, and Brazil produced 8.2 MT. The European Union contributed 3.2 MT.

These oils serve many roles in daily life, from culinary to industrial uses. In cooking, oils provide shortening for pastry texture or act as a flavor base. Some oils, like coconut or rice bran oil, have high flash points. This means they can be heated to very high temperatures for frying without catching fire. Industrially, vegetable oils are used to make soaps, perfumes, and candles. They are also used as insulators in the electrical industry because they are biodegradable. Some oils, like castor oil, are used to create Nylon 11. Others, like dammar oil, are used to treat the hulls of wooden boats.

Vegetable oils also play a critical role in modern energy systems. Rudolf Diesel designed his engine to run on vegetable oil to help farmers. On August 10, 1893, his first engine ran on nothing but peanut oil. This event is now celebrated as International Biodiesel Day. Today, biodiesel is produced through a process called transesterification. It is the most common biofuel in Europe, and in France, it is incorporated into 8% of all diesel fuel. Using vegetable oils instead of fossil fuels can result in greenhouse gas savings ranging from 18% to 100%.