What is rapeseed oil?
I spent a fair portion of my last vacation driving around England and, in mid- to late April, the countryside's distinguishing characteristic was field upon rolling field of blindingly bright yellow blossoms. What is that?, I wondered. Google to the rescue: Searching "England bright yellow fields" informed me it was rapeseed.
In the dim recesses of my brain, I recalled that rapeseed had something to do with canola oil, and I was right. Rapeseed, a member of Brassicaceae (mustard or cabbage family), has been grown for millennia, but its high concentrations of glucosinolates gave it a bitter, cabbagey taste more suited to industrial lubrication than cooking. High levels of erucic acid (a possible cause of heart disease) also conspired to limit its appeal.
In the 1970s, however, scientists began to breed strains of rapeseed that contained lower levels of both glucosinolates and erucic acid. In Canada, the Western Canadian Oilseed Crushers Association (now the Canadian Oilseed Processors Association) came up with the name "canola," a contraction of Canada and ola (oil) to promote the oil. (The name was trademarked, but now canola has become a generic term.)
Canola oil gained popularity because of its nutritional profile (low in saturated fats, containing a healthful 2:1 ratio of omega-6 and omega-3 fatty acids). In its usual highly refined form, it has virtually no flavor or aroma. (Although is it just me or do I often detect a faintly fishy odor?)
Back in Europe, non-Canadian scientists also managed to breed rapeseed that contained lower levels of both glucosinolates and erucic acid, but they kept right on calling it rapeseed. I saw so much of it growing in England that I joked to a friend that I'd have to make sure to buy a bottle of artisanal, single-field, cold-pressed rapeseed oil. She responded that I should have no problem doing so. In fact, the golden oil is a ubiquitous presence on the shelves of specialty stores.
So I bought a bottle of Cotswold Gold Extra Virgin Cold Pressed Rapeseed Oil (about $7.50 for 17.6 ounces) and brought it home. And I can report that it tastes like . . . nothing. No hint of cabbage, but no hint of anything else, either.
Now what is all this cold-pressed, extra-virgin verbiage? Extra-virgin refers to an oil that has been extracted without heat or chemicals and whose level of acidity, in the case of both olive and rapeseed oils, falls below 0.8 percent.
The very best olive (and, I presume, rapeseed) oil is extracted simply by pressing the fruit (or seeds) and letting the oil dribble out -- that's cold pressed. Centrifugal force, heat and even chemical solvents also can be used to extract the oil, and these methods can be used on the mash after that first cold-pressed oil has been extracted. The oil produced by heat and/or chemical extraction must be further treated to clarify and deodorize it. This is called refined olive oil and is of a much lower quality.
The whole point of pressing olives without heat is that the oil retains the distinctive taste and smell of olives. Since cold-pressed rapeseed oil has no discernible taste and smell, I see no reason to spend the extra money. Olive oil, you have nothing to worry about.