Canola

Canola is the name for modern cultivars of rapeseed, mainly Brassica napus, with a small share from Brassica rapa. The plant is an annual, about a metre tall, that covers fields with bright yellow four-petalled flowers in spring. The long, slender pods hold dozens of round black or dark brown seeds about two millimetres across, which are roughly forty percent oil.

Whole seeds are rarely eaten. They are crushed and pressed or solvent-extracted into oil, and the protein-rich meal that remains is used as animal feed. The oil is pale golden and mild, sold as canola oil in the Americas and Australia, and as rapeseed oil in Europe.

Rapeseed arose from a natural cross between cabbage and turnip relatives in the Mediterranean region, and the crop has been grown in Europe and Asia for centuries. The word rape comes from the Latin rapum, meaning turnip, while colza comes via French from Dutch words for cabbage seed.

The name canola is relatively new. In the 1970s plant breeders at the University of Manitoba and Agriculture Canada, notably Baldur Stefansson and Keith Downey, selected varieties low in erucic acid and in bitter glucosinolates. The name was coined for these improved types, combining Canada and ola, for oil, low acid.

Rapeseed oil was used in Asia and Europe for lamps and cooking for many centuries, and by the Middle Ages rapeseed was a significant crop in the Low Countries. In the nineteenth century it lubricated steam engines, because the oil clung well to metal surfaces. In Canada, production surged during the Second World War, when marine engines needed lubricant.

After the war demand fell, and rapeseed oil was found less suitable for food because of its high erucic acid, which raised health concerns, and its glucosinolates, which affected animal feed. Through the 1960s and 1970s Canadian scientists bred varieties with greatly reduced levels of both, and the new crop was named canola in 1978. It rapidly became one of Canada's most important crops.

Canola is now grown across Canada, Europe, China, India, Australia and elsewhere. Much of the North American crop is genetically modified for herbicide tolerance, whereas European production is conventionally bred. The oil is popular for its mild taste, high smoke point and balance of monounsaturated fats with some omega-3 content, and it is also used to make biodiesel.

Canola's main use is as a liquid cooking and salad oil, valued for its neutral flavour. It is also the base of margarines, mayonnaise, dressings and many processed foods, and is used for frying and baking. Cold-pressed rapeseed oil, popular in northern Europe, has a more nutty flavour.

The leftover canola meal is a major protein feed for livestock and fish, and the oil is a feedstock for biodiesel. Canola protein isolates are being developed for human foods. The plant's flowers produce a mild, quickly crystallising honey, and the seeds are occasionally sold for sprouting or pressing at home.

Canola oil is low in saturated fat and rich in monounsaturated fat, and contains a modest amount of plant omega-3 (alpha-linolenic acid). Replacing saturated fats such as butter with unsaturated oils like canola is generally associated with lower LDL cholesterol, and major health bodies include it among acceptable cooking oils.

Online claims that canola oil is toxic are not supported by the scientific evidence on modern low-erucic varieties. As with any oil, it is energy dense, and heavily reheated oil in deep-frying can produce undesirable compounds.