Rapeseed meal composition

Table I. Amino Acids Composition of Defatted Canola (Rapeseed) and Sunflower Meals (19)...

The seeds contain 40-50% oil and 20-25% protein (dry matter basis [3]). Originally, the fatty acid with the highest share was erucic acid with 25-50% in the seed oil. Due to the negative nutritional effects attributed to eracic acid in Western countries, and because of glucosinolate contents, the composition of rapeseeds prevented the use of the oil for food and the use of the meal for fodder. 

Apart from price and availability considerations, the composition of an oil is only one of the factors that enter into decisions to choose one oilseed over another in world markets. Two other important considerations are the proportion of meal in the seed and the quality of the meal. For example, soybeans contain only 18% oil hence a much higher proportion of their total value lies in the high protein meal than in the oil. Conversely, rapeseed peanuts, sunflower, and cottonseed contain 30-40% oil, therefore oil is the more valuable component. Then the quality of the meal becomes a very critical factor in determining the commercial value of one oilseed versus another. Sunflower seed, for example, produces an inferior meal, which is high in fiber and low in protein (23%) meals from cottonseed and peanut are of medium quality. 

The magnitude of the variation in the composition of rapeseed oil and meal now commercially available has created a need for new terms to describe the products derived from rapeseed. The fatty acid composition of most edible vegetable oils such as soybean, sunflower, or cottonseed oils, varies within narrow limits. Thus, the species or commodity name (e.g., soybean oil) provides a reasonable description of the fatty add composition of soybean oil. In contrast, the erucic acid content of commercially available rapeseed oil may vary from near zero to 55%, and the oleic acid from 10 to more than 60%. A number of terms have been proposed or utilized to describe the new rapeseed oil whose fatty acid composition has been altered by the elimination of erucic acid these include low erucic acid rape-seed oil (LEAR), canbra, and canola. Similar terms such as high erucic acid rapeseed oil (HEAR) and common or traditional rapeseed oil have been used to describe rapeseed oil whose fatty acid composition includes substantial amounts of erucic acid. 

Most of the rapeseed produced in the Orient is of the traditional kind, high in both erucic acid and glucosinolates. Little attention appears to have been given to the development of canola cultivars. Perhaps the need to increase food supplies discourages the deployment of resources for work on quality. Prakash (1980) suggests that alteration of the composition of the oil and meal is one of a number of possible future trends in India. The recent increase in international contacts probably will stimulate the development of canola cultivars in China. 

The two major changes in the composition of rapeseed, which have been made available commercially, have improved the nutritional value of the oil and meal. Further improvements probably will become commercially available during the present decade. The possibilities for changes in chemical composition of crops probably are not limited to rapeseed the changes made in rapeseed may thus provide an indication of the manner in which other crops might be modified to provide better food and feed. 

The proximate composition of canola/rapeseed varies among varieties as a result of both genetic makeup and growing conditions. As summarized in Table 4.3 [4], the oil content of canola is about twice that of soyabeans and contains much more fibre than soyabeans. The protein content of oil-free canola meal is only slightly lower than that of soyabeans. Canola is processed primarily for its oil, which makes up some 40% of the seed mass. It has an ideal fatty acid composition for human consumption, with a linoleic-to-linolenic acid ratio of approximately 2. After oil removal, the meal contains more than 40% protein with well-balanced amino acid composition. The essential amino acid composition, given in Table 4.4, indicates that canola protein is superior... 

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