HEAR high erucic acid rape seed

LEAR, low erucic acid rape seed oil. HEAR, high erucic acid rape see oil. 

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. 

Currently available cultivars of high erucic acid rape (HEAR) have a theoretical maximum of 66% erucic acid (22 1, A13) in their seed oil due to the specificity of the membrane-bound l-acyl-572-glycerol-3-phosphate acyl transferase (LPA-AT) enzyme. In HEAR the LPA-AT does not incorporate erucic acid at the sn-2 position of triacylglycerols (TAG) but preferentially incorporates oleic acid (18 1, A9), even if this is only a minor component of the total fatty acid pool (1). However, some plant species, Q.g Limnanthes, can utilise erucoyl-CoA as a substrate and effectively incorporate erucic acid at the sn-2 position (2, 3). 

To study the membrane associated enzymes involved in elongation in oil seed rape Brassica napus), a high erucic acid rape (HEAR) variety was used. Low erucic acid rape variety contains a mutation which prevents elongation of 018 1 fatty acids. As the nature of the mutation is not known, and could be in the elongating enoyl reductase, HEAR was used throughout these studies. 

By way of a specific example let us consider erucic acid. The main commercial source of erucic acid is a specially bred form of rape seed (HEAR) as pointed out above. With European consumption being around 60 000 tpa almost 40 000 ha of land are used to grow rapeseed for erucic acid production in Europe. The high level of erucic found in this type of rape seed oil make it unsuitable for human consumption, owing to the indigestibility of such large amounts of this acid. Erucic acid is also the major fatty acid to be found in nasturtium and crambe seeds (up to 75% and 56% respectively), and it is also found in the salad herb, rocket. 

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