234 – II.3. BRASSICA CROPS (BRASSICA SPP.)
became an important constituent of margarine. Researchers became interested in the
nutritional value of Brassica seed oils because they differed from most other edible oils in
having a high percentage of long carbon chain monoenoic fatty acids, eicosenoic (C20:1)
and erucic (C22:1) (Table 3.14).
Small animal feeding studies in the late 1950s and throughout the 1960s indicated that
the nutritional value of rapeseed oil could be substantially improved if the long chain
fatty acids could be reduced to <5% of the fatty acid total (Kramer et al., 1983). Breeding
and selection within the world’s germplasm was successful in developing plants of
B. napus (Stefansson, Hougen and Downey, 1961), B. rapa (Downey, 1964) and later
B. juncea (Kirk and Oram, 1981) that produced oils with less than 2% erucic acid.
This oil was found nutritionally superior to the high erucic oil (Kramer et al., 1983) and
proved to be an excellent liquid and salad oil, as well as a suitable ingredient for
margarine and shortening manufacture. This new natural oil is called “canola oil” in most
countries of the world and is defined as oils from B. napus, B. rapa or B. juncea
containing less than 2% erucic acid of the fatty acid total. The genetic blocking of the
biosynthesis of eicosenoic and erucic acids resulted in an increased percentage of oleic
and linoleic acids (Table 3.14).
oils Table 3.14. Fatty acid composition of rapeseed, canola, soybean, sunflower and linseed
Fatty acid Symbol^1
Rapeseed Canola Soybean Sunflower Linseed
Fatty acid composition (%)
Palmitic C16:0 4.0 4.7 11.5 7.5 7.0
Stearic C18:0 1.5 1.8 3.5 4.5 4.0
Oleic C18:1 17.0 61.5 23.0 16.0 20.0
Linoleic C18:2 13.0 21.0 43.0 71.0 17.0
Linolenic C18:3 9.0 11.0 8.0 1.0 52.0
Eicosenoic C20:1 14.5 <1.0 0.0 0.0 0.0
Erucic C22:1 41.0 <1.0 0.0 0.0 0.0
Note: 1. The first number denotes the number of carbon atoms in the fatty acid chain and the second numbe,
the number of double bonds in the chain.
When nutritionists recommended that dietary intake of saturated fat be reduced, the
nutritional value of canola oil gained widespread recognition since it contains the lowest
level of saturated fatty acids of any edible oil (Grundy and Denke, 1990; Gurr, 1992;
Hu et al., 1997; see Figure 3.41). Further, in 1985 Mattson and Grundy reported on the
nutritional desirability of the so-called “Mediterranean diet”, pointing out the health
advantages of oils with a low level of saturates and high content of oleic acid. The fatty
acid composition of canola oil met or exceeded the nutritional requirements of a superior
edible oil, with the lowest saturate content (6-7%) of any edible oil and a high (58-60%)
level of oleic (18:1n-9) that reduces the undesirable low-density lipoproteins (LDLs)
without reducing the desirable high-density lipoproteins (HDLs).
Plant breeders have now developed varieties that produce canola oils with less than
3% α-linolenic acid which improves the oxidative stability of the oil and reduces the
development of unpleasant flavours and cooking odours (Scarth, Rimmer and McVetty,
1995; Scarth et al., 1988; Eskin et al., 1989; Przybylski et al., 1993).
