Detection of sunflower and soybean oil adulterated with rapeseed oil

摘要

Erucic acid, #alpha#-linolenic acid and brassicasterol were tested as markers proving the adulteration of sunflower and soybean oils with rapeseed oil. The results of the analyses of plant oils showed that erucic acid can only be used as a marker of such adulteration by massive additions of rapeseed oil. The mason of this is its low and fluctuating content in oils produced from non-erucic rapeseed (rapeseed oils in quality "00" - averaging 0.4% of total fatty acids). This was a source of difficulties in cases where low additions of rapeseed oil were determined and the content of erucic acid fluctuated near the detection limit of the analytical method used. Similarly, #alpha#-linolenic acid can only be used as a supporting marker of the presence of rapeseed oil, due to the permitted range of its content in sunflower oil. Brassicasterol appeared as a highly indicative marker, which was lacking in both sunflower and soybean oils, but was found in rapeseed oil, averaging 1400 mg/kg. Its peak could be identified very easily in chromatograms, with the possibility of calculating the probable amount of rapeseed oil added. A spot-check survey of the incidence of this kind of plant oil adulteration was carried out in retail outlets. Its results indicate that sunflower and soybean oils of both local and foreign provenance, or their mixtures, containing lesser to major addition (3-25%) of rapeseed oil, are sold rather frequently in this country.