Rape oil

Promotion to high-quality cooking oil

Oilseed rape is a relatively new crop. Up until a few years ago the oil made from pressed seeds was unpalatable. This is no longer the case: modern rape varieties produce high-quality cooking oils. Today rape is the most important oil seed grown in Germany.

Oilseed rape belongs to the Brassica family (crucifers) and is closely related to our cabbage varieties. It resulted from a cross between wild cabbage (Brassica oleracea) and wild turnip (Brassica rapa). Rape probably comes from the Mediterranean, where the geographic ranges of the two parent species overlap.

Rape oil. It must come from 00 varieties in order to be palatable. Rape oils normally need refining: high pressures and temperatures are used to purify the oils and remove slimy and bitter substances.

Rape has an oil content of 40% and was known even in Roman times. But it was not grown as an agricultural crop until the 17th century. Cooking oil made from pressed rape seeds used to have a poor reputation. This was due to its bitter taste, which, as we now know, resulted from a high erucic acid content.

Rape provided fuel for oil lamps right up until the modern day. In times of need when hunger threatened or when fats were in short supply, however, rape was also used as cooking oil. During both world wars rape cultivation in Germany was strongly encouraged to break the dependence on fat and oil imports. Margarine in particular was made from homegrown rape oil.

Unfit for table oil and unsuitable for animal feed, the use of rape was limited to industrial oils. This changed abruptly when rape varieties with two new characteristics came onto the market in the mid-seventies: The oil from this 00-rape ("double-zero") only contains small quantities of the bitter-tasting erucic acid. In addition the rape seeds were virtually free from glucosinolates. These toxic substances had precluded the use of rape as animal feed in the past.

Rape oil for consumption

Since farmers began growing the new 00 varieties, rape oil has found favour in the food industry - not just as a raw material for margarine, but also as a cooking oil. In 1974 seventy percent of rape oil production was used in the industrial sector, whereas today the main consumer is the food industry.

	Saturated fatty acids	Mono- unsatu- rated fatty acids	Poly- unsatu- rated fatty acids
Rape oil	6 %	69%	28%
Thistle oil	10%	12%	75%
Sunflower oil	12%	22%	61%
Olive oil	14%	73%	9%

Fatty acid composition of various cooking oils. Mono- and polyunsatu-
rated fatty acids contribute to a lowering of cholesterol levels in the blood

To make it taste as neutral as possible, rape oil is normally purified after pressing (refining ). Turbidities, mucilages (slimy substances) and bitter principles are removed by applying heat, pressure and solvents. If plant oils are to be used as spreads, they also have to undergo a hardening process . In a process controlled by specific catalysts, the liquid oils are converted to spreadable fats by modifying the chemistry of certain fatty acids.

In nutritional physiology terms, rape oil is a valuable cooking oil. Compared to other plant oils it has the highest amount of unsaturated fatty acids (91 g/100g) and the lowest proportion of saturated fatty acids. In terms of mono-unsaturated fatty acids it is outclassed only by olive oil, which contains more saturated fatty acids.