Identification of Waxes in Canola Oil

Canola has the lowest content of saturated fat amongst oils marketed in North America, and therefore is a valuable nutritional component for food industry and household use. Oils, extracted from vegetable tissues, contain a number of impurities which have to be removed in order to make the oil suitable for human consumption. One such impurity consists of waxes, which are high melting esters of fatty alcohols and fatty acids, having a low solubility in oils. These waxes make the oil cloudy at lower temperatures. The quantity of waxes in crude oils varies from several hundred ppm to several thousand ppm. If the refined vegetable oil is cooled or stored for prolonged periods of time, then any vegetable waxes present will crystallize and either impart a cloudy appearance to the oil or settle out as a crystalline precipitate. Without further processing (winterization) such vegetable oils are not suitable for market purposes, where the clarity of the oil at lower temperatures or subject to prolonged storage is important. Generally, the method for dewaxing oil consists of carefully cooling the oil followed by crystallization of the wax, which is then removed by centrifugation or filtration. However, winterization is an expensive and energy consuming process and should not be used indiscriminately, especially since the level and characteristics of waxes in canola oil may vary according to crop, variety, climate and soil type. Therefore the ability to recommend winterization to processors and monitor and efficiency of wax removal is an important marketing support tool. Methods currently used for wax determination are unreliable, time consuming and require substantial manual operation. Our objective in this study was to develop a reliable method for direct wax analysis in canola oil, based on high-performance liquid chromatography. We took advantage of new evaporative scattering laser light detector (ESLD) for quantitation of waxes, and combined this technique with Gas Liquid Chromatography (GLC) and mass spectrometry for identification of the waxes. This method allows the performance of automatic and quicker separations of wax esters and provides canola crushers with a valuable monitoring tool. BACKGROUND AND OBJECTIVES Canola oil has been recognized by the general public as a valuable oil based on several important factors: growing awareness of its nutritional properties, development of new canola varieties with altered fatty acid profile and lower glucosinolate level, improvement in processing of canola oil, aggressive marketing approach both in Canada and worldwide. Canola has the lowest content of saturated fat amongst oils marketed in North America (1), and therefore is a valuable nutritional component for food industry and household use. Oils, extracted from vegetable tissues, contain a number of impurities, which have to be removed in order to make the oil suitable for human consumption. The removal of impurities from the vegetable oils is commonly referred to as refining. However, known refining methods do not remove higher melting triglycerides nor linear waxes from these oils. One such impurity consists of waxes, which are high melting esters of fatty alcohols and fatty acids, having low solubility in oils. These waxes make the oil cloudy at lower temperatures. The quantity of waxes in crude oils varies from several hundred ppm to several thousand ppm. The wax content has to be reduced to the level of about 10 ppm or less, so the cold stability of the oil is improved. If the refined vegetable oil is cooled or stored for prolonged periods of time, then any vegetable waxes present will crystallize and either impart a cloudy appearance to the oil or settle out as a crystalline precipitate. Without further processing (winterization) such vegetable oils are not suitable for market purposes, where the clarity of the oil at lower temperatures or upon prolonged storage is important. Numerous methods for dewaxing and winterizing vegetable oils have been reported. Generally, the method for dewaxing oil consists of carefully cooling the oil followed by crystallization of wax, which is then removed by centrifugation or filtration. However, winterization is an expensive and