Oilseed rape: evolution of a golden food

The early bloom of golden fields full of all seed rape has hit the news this year. Partly because it appears so ubiquitous, with the yellow sometimes reaching to the horizon. But the oil from oilseed rape was not so highly prized in the past. It has taken scientists, plant breeders and farmers working together to transform what used to be a lamp oil into a prized nutritional food.

Oilseed rape fields in Cambridgeshire

 Originally oilseed rape was grown as a break crop, that is, it was part of the farming rotation cycle. Growing rape for one year within the cycle resulted in soil improvement. The oil was primarily good for lamp oil and machinery use. In the previous century it could also be added to animal feed, but only to a certain degree because it had a bitter taste.

The bitter taste was due to glucosinolates, or mustard oils. Oilseed rape after all belongs to the mustard family. Rape varieties also had up to 50% erucic acid, a compound with suspected cardiac health risks, that led it to being banned for inclusion in human consumption in the US FDA back in 1956.

However in the 70s, Canadian agriculturalists developed a variety of oilseed rape that was low in both glucosinolates and erucic acid, which led to the other common name, Canola, for Canadian Oil Low Acid. Since then the cultivation and use of oil seed rape for human consumption has also increased, with coldpressed oils reaching a premium price. The health benefits were low levels of saturated fat (7%, compared to butter 52%) and the presence of omega-3 and omega-6.

American oilseed rape has become infamous in Europe, as 90% of that grown in the USA is now GM, with resistance to herbicides. Europe only grows GM free oilseed rape.

There is another current issue with growing oilseed rape, the oil-rich seeds are spread explosively when the ripe pods shatter. Current losses are estimated anywhere between 15 to 50%, with heavy rain and wind promoting shattering. Plant geneticists have therefore been searching for oilseed rape plants with more shatter resistant pods. A total resistance to shattering is actually undesirable, because otherwise it would be difficult to extract the seeds to propagate the plant! Work at the John Innes Institute in Norwich is amongst those that are making advances in this area. And last year Bayer released its first new increased shatter resistant variety, InVigor L140P, in Canada.

Flower, oilseed rape

Britain now produces over 3,000,000 t of rapeseed oil per year. The ubiquity of the plant in fields at this time of the year has also been associated with complaints by allergy sufferers. The plant is blamed for an increase in hayfever and irritation.

Oilseed rape pollen, like any flower pollen, can be highly allergenic. However the plant is insect pollinated and produces very sticky pollen that does not get into the air easily.

Furthermore, the flowering season coincides with mass pollen release by trees that RELY on wind dispersal, examples are Hazel, Yew, Alder, Elm, Poplar, Willow, Birch, Oak and Pine. Tree pollen is a major cause of hayfever from February through to May, after that the grass pollens hit us sufferers.

Dry pollen from flower

Pollen in liquid

However, oilseed rape fields can irritate sensitive noses on a warm sunny days, due to the distinctive slightly acrid scent and oils that they emit.

The vast fields of oilseed rape do provide a vital source of food for pollinating insects. Indeed without insect pollination, seed production would cease. Whilst natural hover flies, beetles of solitary bees and bumblebees are of great benefit here, honeybees can also make a contribution, producing a slightly peppery honey as a byproduct.

A few weeks still remain to either enjoy or curse the golden fields, before their seed production begins and later harvest beckons.

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