| The price differences of Vegetable oils resulted from production,nutritional value and uneven distribution of vegetable oils. Some uncrupulous made an illegal means, mixing cheap oils into high oils to seek high profits,which greatly damaged the interests of consumers. In order to rectify and regulate the oils market, the need to take a means of identification of adulterated oils was easy to favorably against the adulteration of commercial oils.The paper established the standard fingerprint by GC-MS,and made the comparative and the similarity analyze the fatty acid of oils to qualitative identification of vegetable oils,which provie the basis to the adulteration model established of vegetable oils. The results of this paper was as follows:(1)It studied on the methylesterification pre-treatment of GC-MS analysis of fatty acid in vegetable oils by KOH-methanol solution method and H2SO4-methanol solution method.It determined the affects of the oscillations of temperature and time,the contents of methanol solution with KOH-methanol solution method and H2SO4-methanol solution method on the conversion efficiency of the oleic acid methyl ester by the single factor experiments and orthogonal test,in order to decided to the optimized condition of KOH-methanol solution method and H2SO4-methanol solution method.Combining these two methods derived from acid-alkali combination method. Compared with three methods,it was finally determinated to the best way of methylesterification reation,called acid-alkali combination method,the conversiton efficiency of the oleic acid methyl ester by which was 95.5%.(2) It was estabalished to the standard fingerprint of the seven major oils by the common pattern method and by the method to directly choose the representation of the GC-MS fingerprint. It was established to the standard fingerprint of rapeseed oils, soybean oils, cottonseed oils, peanut oils and camellia oils by the common pattern method and the standard fingerprint of palm oils and sunflower oils by the method to directly choose the representation of the fingerprint because of oil samples less.Then,it was calculated to the similarity of the standard fingerprint of rapeseed oils, soybean oils, cottonseed oils, peanut oils and camellia oils by the common pattern method and all the samples of each oils interrelated to this standard fingerprint,which determined the similarity of rapeseed oils,soybean oils, peanut oils, cottonseed oils and camellia oils larger than 0.998,0.976,0.998,0.997,0.996.It indicated that all the standard fingerprint established by common pattern methods was consistent with the whole information of the fatty acids in each oil. It caculated the similarity of the standard fingerprint by the common pattern and by the method to directly choose the representation of the GC-MS fingerprint,which found the differences between the standard fingerpring of each oil,which reflected the differeces between each oil. It indicated that all the standard fingerprint was the differences of the fatty acids in each oil. At the same time,compared with the compositon and content of fatty acids in the seven major oils,it found that peanut oils had Hexacosanoic acid,higher content of Arachidic acid and Lignoceric acid,and rapeseed oils had nervonate acid and higher content of Linolenic acid.(3) It studied on the identification method of adulterated oils by the similarity analysis.It was caculated to the similarity of each adulterated oil and all the standard fingerprint through mixing cheap oil with different ratios of 5%,15%,25%,50% into high oil simulated the adulterated oil.It can qualitatively identify the adultertion oils with the similarity between all the standard fingerprint and the similarity of adulterated oils.(4) It studied on the identification method of adulterated oils by comparative analysis. Depended on these characteristic of vegetable oils, it drew two-dimensional diagram by the cis-oleic acid methyl ester/cis-linoleic acid methyl ester, palmitic acid methyl ester/stearic acid methyl ester.By the comparative analysis of which,it qualitatively identified the adulteration of oils. |
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