Cultivation and Uses
Rapeseed oil was produced in the 19th century as a source of a lubricant for steam engines. It was less useful as food for animals or humans because it has a bitter taste due to high levels of glucosinolates. Varieties have now, however, been bred to reduce the content of glucosinolates, yielding a more palatable oil. This has had the side effect that the oil contains much less erucic acid.
Rapeseed is grown for the production of animal feed, vegetable oil for human consumption, and biodiesel; leading producers include the European Union, Canada, the United States, Australia, China and India. In India, it is grown on 13% of cropped land. According to the United States Department of Agriculture, rapeseed was the third leading source of vegetable oil in the world in 2000, after soybean and oil palm, and also the world's second leading source of protein meal, although only one-fifth of the production of the leading soybean meal.
World production is growing rapidly, with FAO reporting 36 million tonnes of rapeseed were produced in the 2003-2004 season, and estimating 58.4 million tonnes in the 2010-2011 season. In Europe, rapeseed is primarily cultivated for animal feed, owing to its very high lipid and medium protein content.
Natural rapeseed oil contains 50% erucic acid. Wild type seeds also contain high levels of glucosinolates (mustard oil glucosindes), chemical compounds that significantly lowered the nutritional value of rapeseed press cakes for animal feed. In North America, the term "canola", originally a syncopated form of the abbreviation "Can.O., L-A." (Canadian Oilseed, Low-Acid) that was used by the Manitoba government to label the seed during its experimental stages, is widely used to refer to rapeseed, and is now a tradename for "double low" (low erucic acid and low glucosinolate) rapeseed.
The rapeseed is the valuable, harvested component of the crop. The crop is also grown as a winter-cover crop. It provides good coverage of the soil in winter, and limits nitrogen run-off. The plant is ploughed back in the soil or used as bedding. On some ecological or organic operations, livestock such as sheep or cattle are allowed to graze on the plants.
Processing of rapeseed for oil production produces rapeseed meal as a byproduct. The byproduct is a high-protein animal feed, competitive with soya. The feed is mostly employed for cattle feeding, but also for pigs and chickens (though less valuable for these). The meal has a very low content of the glucosinolates responsible for metabolism disruption in cattle and pigs. Neither canola nor soy is recommended as feed for organic animal products, as both are predominantly GMO (some estimates are now at 90%), which is prohibited by organic standards.
Rapeseed "oil cake" is also used as a fertilizer in China, and may be used for ornamentals, such as bonsai, as well.
Rapeseed leaves and stems are also edible, similar to those of the related bok choy or kale. Some varieties of rapeseed (called 油菜, yóu cài, lit. "oil vegetable" in Chinese; yau choy in Cantonese; cải dầu in Vietnamese; phak kat kan khao in Thai; and nanohana /nabana in Japanese) are sold as greens, primarily in Asian groceries, including those in California, where it is known as yao choy or tender greens. They are eaten as sag (spinach) in Indian and Nepalese cuisine, usually stir-fried with salt, garlic and spices.
Rapeseed produces great quantities of nectar, and honeybees produce a light-colored, but peppery honey from it. It must be extracted immediately after processing is finished, as it will quickly granulate in the honeycomb and will be impossible to extract. The honey is usually blended with milder honeys, if used for table use or sold as bakery grade. Rapeseed growers contract with beekeepers for the pollination of the crop.
"Total loss" chain and bar oil for chainsaws have been developed which are typically 70% or more canola/rapeseed oil. These lubricants are claimed to be less harmful to the environment and less hazardous to users than traditional mineral oil products, although they are currently typically two to five times more expensive, leading some to use inexpensive cooking oil instead. Some countries, such as Austria, have banned the use of petroleum-based chainsaw oil. These "biolubricants" are generally reported to be functionally comparable to traditional mineral oil products, with some reports claiming one or other is superior, but with no overall consensus yet evident.
Rapeseed has also been researched as mean of containing radionuclides that contaminated the soil after the Chernobyl disaster. It was discovered by researchers at the Belarusian Research Institute for Soil Science and Agrochemistry that rapeseed has an rate of uptake up to three times more efficient than other grains, and only about 3 to 6% of the radionuclides goes into the parts of the plant that could potentially enter the food chain. As oil repels radionuclides, it could be produced canola oil free from contaminants being concentrated in other parts of the plant – the straw, the roots, the seed pods, etc, which then can be plough back into the soil and create a recyling process.
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