Formation Of Benzopyrene In Processing Of Sesame Oil

Sesame oil is one of the traditional edible oils of China. The process of sesame seedhigh-temperature roasted not only obtains color, flavor, but also easily leads to excessivelevels of highly carcinogenic benzopyrene. Firstly, the determination of benzopyrene insesame oil had been identified and optimized. Then the variation of benzopyrene content hadbeen studied in the whole process of sesame oil: different roasting conditions had beenchanged to explore the formation of benzopyrene, and so did the sesame oil extractionmethods. Finally, four main components of sesame seed(fats, proteins, polysaccharides andcrude fiber) were roasted as different combinations, the content of benzopyrene and thecomponents of the tar were determined,on the basis of which the generated of benzopyreneduring sesame oil processing has been explored preliminarily.The HPLC-FLD had been choosed to determine the content of benzopyrene in sesame oil,according to the comparison of HPLC-FLD and GC-MS. This method used commerciallyavailable alumina column for sample handling, its recoveries were in the range of82%-96%,with high precision (RSD <8%), and good linearity (R2=0.9999) betwttn a concentrationrange of0.5-50μg/kg, the limit of detection was0.12μg/kg. Benzopyrene of23commercialsesame oil samples were measured, indicating that the samples were subjected to varyingdegrees of benzopyrene contaminations range from0.57μg/kg to10.95μg/kg, in which onesample content over10μg/kg, and13samples were more than2μg/kg.Benzopyrene increased with roasting temperature raising, and the impact of roasting timeand the amount of oxygen was not obvious, so as the smoke elimination and moisture of rawmaterial. Benzopyrene of cold-pressed sesame oil was much less than the hot-pressed oil, thisproved that benzopyrene mainly generated in the high temperature roaste process andconcentrated in the crude oil extraction. Crude oil obtained by hexane extraction had muchmore content of benzopyrene than that of aqueous extraction method, this was caused by thedifference of the two extraction principles of the solvents. Benzopyrene was decreased in therefining process of the sesame oils with four processes, in which cold-pressed oil and aqueousextraction oil were below2μg/kg, however, hot-pressed oil and hexane extraction oil werestill high, although both of them below10μg/kg. Most benzopyrene was generated by the combination of oil and protein in heatingprocess, and cellulose may be offered some initial material or intermediate groups to assist theprocess. Tar components analyzed by GC-MS showed that the most abundant of the tar waswhole sesame, in which a range of possible intermediates of benzopyrene were formed. Thesemolecules appeared to have a certain regularity: the side chain of benzene ring graduallyextended, and the degree of unsaturation increases, along with an increase in the number ofbenzene rings. Conversely, constituents of sesame coat and sesame seed tars were fewer, butinclude more volatile fumes. The formation of benzopyrene can be speculated as follows:organic components such as cellulose, pyrolysis of ethylene, acetylene or1,3-butadiene andother small unsaturated molecules, combine to forming unsaturated long chains hydrocarbonsrapidly, the hydrocarbons cyclize to aromatic compounds further, and the side chain activesite of the benzene ring random cracking of various free radicals which increases the benzenering in combination with each other, benzenepyrene formated through the dehydrogenationand condensation reaction finally.