Description & Cultivation
Rapeseed, also called colza, is a member of the Cruciferae family and grows to a height of 75-175 cm. It has yellow flowers, blue-green leaves and is heavily branched with deep, fibrous taproot. The seeds are small, round and black-red in colour.
What we today term rapeseed actually comprises several different varieties within the Brassica family which are very similar: Brassica napus (rapeseed) and Brassica rapa (turnip rapeseed).
Rapeseed is one of the oldest cultivated plants on earth, from antiquity right down until the nineteenth century; rapeseed oil was used mainly for lighting and as a lubricant, today, rapeseed oil is one of the most important vegetable oils for human consumption.
Rapeseed has become the special oil plant of Northern Europe. Large areas are cultivated in the European Union, Poland and the Czech Republic. Outside Europe the dominant producers are China, India, Canada and Australia.
Rapeseed is planted either in the autumn (winter varieties) or in the spring (summer varieties). The winter varieties have a longer vegetation period and give a better yield, but can only be grown in areas with a mild winter climate. In Europe winter rapeseed is the dominating variety, whereas in Canada only summer rapeseed is grown. The harvest period in the Northern Hemisphere starts in late July for the winter varieties, in late August or early September for the summer varieties.
The EU produces 24 million tonnes of rapeseeds, imports 3 million tonnes and exports about 0.5 million tonnes. The crushing of rapeseeds in the EU accounts for 24.6 million tonnes.
Rapeseed oil and meal
As the oil content of rapeseed is around 43 %, the processing is usually made in two steps: pre-pressing plus solvent extraction. Sometimes only deep-pressing is applied.
The rapeseed meal is an important protein source in compound feed for cattle, pigs and poultry.
Rapeseed oil contains 98 % of tri-esters of fatty acids and 2 % of sterols and tocopherols. It has a uniquely low content of saturated fatty acids and a high content of monounsaturated fatty acids, offering a good balance of fatty acids: 60 % oleic, 20 % linoleic, 10 % alphalinoleic. It is also a rich source of Omega 3 and Omega 6 linolenic acids.
The low erucic variety is widely used for applications such as salad dressing, margarines and sauces. The high erucic variety is used in a range of technical purposes, for example bio-degradable lubricating oil as an alternative to mineral oil based lubricants. The use of rapeseed oil methyl esters as a substitute for diesel fuel takes large volumes of rapeseed oil.
Rapeseed meal, with only 34 % protein content can hardly substitute soymeal in animal feeding. It represents 7 % of the vegetable meals consumed in Europe and can enter feed ratios in the proportion of maximum 15 % for chickens and 20 % for porks and milk cows.