1.2.7 Rape and mustardseed

Rapeseed and mustardseed are both obtained from species of Brassica in the family of the Cruciferae which includes some 160 species, mainly annual and biannual herbs. Of rapeseed, the two most important oilseed producers are B. campestris L., which has a fairly wide world distribution, and B. napus L., which is basically restricted to Europe and North Africa. Of mustardseed, B. juncea is the most common and known as Chinese or Indian mustard or rai. Because of the similarity of the species, the present chapter will refer to them as “rape" and summarize the characteristics.

Figure 8: Mustard.

Source: KIT, 1979

The origin of rape is most likely the South and East Asian region, since the oldest known references to its cultivation are from India, China and Japan. Secondary centres could be in the Mediterranean area. Whereas in the West and East, rape was originally cultivated for its roots and leaves (as a food), in India the seed was selected for its oil, and this started the wider distribution of the crop. Rapeseed's major use then became the production of oil for industry or domestic lighting. As an edible oil, rapeseed was initially only used by poor people, but the development of new technologies has increased its attractiveness for human consumption and animal feed. Mustardseed has long been used for spices.

Today, rapeseed and mustardseed rank with about 19 million tons sixth in world production of major oil plants and with 6 million tons fourth in vegetable oils (see Tables I and 2). Major seed producers are China, Canada, India and France (in that order for 1985), main oil producers are Europe, Canada and Japan. World trade in rape and mustard oils has been steadily increasing since the 1960's with volumes currently around 1.3 million tons. Surprisingly, with 75 % of the trade, exports are dominated by European countries (Federal Republic of Germany, France and others); other major producers, like Canada, are still increasing their market share. Production and exports from Africa are negligible, North African countries, in fact, importing one third of all commercially available quantities.

Oilseed rape and mustard are basically temperate crops which prefer moderate temperatures below 25°C during growth. Breeding and selection has considerably increased the geographic range of cultivation with hardy varieties being able to withstand long periods of snow cover and very low temperatures and others able to withstand more than 40°C for a limited period during the vegetative phase. Optimal rainfall is considered to be 700 mm per year. Rape will still produce a good crop using mainly residual soil moisture, provided some rain falls between planting and the seedling stage and at main flowering. These characteristics are of particular advantage in tropical regions of high altitude with significant temperature variations-and low rainfall.

Yields per ha can reach more than 3 tons of seeds under optimal conditions (Europe), but on average yields are just over 1.2 tons/ha. The protein content of the seeds varies from 10% to 45%, the oil content is normally in the range of 30 % to 50 %, but can reach up to 60%.

Rapeseed oil is dark, but after refining becomes light yellow and resembles sunflower oil. The colour is influenced by the seed chlorophyll level. A low value produces a light coloured oil which is commercially desirable. In the past, oil produced from the higher yielding varieties contained high levels of erucic acid, which constitutes a health risk for human consumption. Breeding has led to varieties without this acid. Oil from older varieties is mainly used for technical purposes.