| This experiment studied the polar components and quality deterioration of frying oil by using different detection analysis technology. The column chromatography was used to determine the content of polar compounds of frying oil. Analysis the influence of different fring time, fring temperature and frying oil varieties on the polar components content. The chemical index such as peroxide value, acid value, carbonyl value fatty acid components were used to study the quality changes of frying oil.Having determined absorption peak intensity in frying oil by TLC method under the condition 254 nm to investigate the relationship between the absorption peak intensity and polar components content. For a thorough understanding of polar components of structural components, on this basis, having analyzed the the volatile and non-volatile polarity composition structure of frying oil using solid phase microextraction / GC-MS and high performance liquid exclusion chromatography.(1)Firstly this experiment determined the contend of polar components by using column chromatography in the frying process for 30 h under the condition of 190 ℃ and analysised the the influence of frying time, frying temperature, different varieties of frying oil to polar components content.The results showed that the contend of polarity component increased with the increasing of the frying time and frying temperature, and the content of polarity components of different varieties was different.And the more of unsaturated fatty acid content the higher of the cintent of polar components in the frying process. After Fried for18 h the polarity components contend of soybean oil, sunflower oil, corn oil, rice bran oil increased from 5.20%, 3.80%, 3.26%, 19.60% to 23.20%, 26.60%, 22.67%, 32.00% under the condition of 190 ℃,which were more than or close to the polar components content 27%,limited by GB 7102.1 2003 in frying process.The acid value, peroxide value and carbonyl value were determined by the method of national standardunder the condition that fried vegetable oils for 30 h under 190℃. Compared with the crude oil after fried the acid value, peroxide value and carbonyl value changed all. The acid value increased with the extension of frying time. But the whole process were nol more than the limit of GB 7102.1-2003(≤5.0 mg/g). Oxidation value increased at the first time, but then decreased. Carbonyl value overall showed a trend of increasing. When the frying time reached to 18 h, the carbonyl value of soybean oil, sunflower oil, corn oil, rice bran oil reached to 65.57 meq O2 / kg, 70.87 meq O2 / kg, 62.85 meq O2 / kg, 59.98 meq O2 / kg,which have been close to or exceed the limit of GB 7102.1 2003 about frying oil(≤50 meq O2/kg).The fatty acid composition and content were determined by the method of gas chromatography under the condition that Fried vegetable oil or 30 h under 190℃. The unsaturated fatty acids Vegetable oil were mainly composed of oleic acid, linoleic acid and linolenic acid, unsaturated fatty acids were mainly composed of palmitic acid and stearic acid.The trans fatty acids were given priority to t18:1, t18:2, t18:3. when oil was fried under 190℃.The content of t18:1, t18:2, t18:3 were gradually increasing with the extension of frying time.And the content of palmitic acid, stearic acid, oleic acid increased,but The content of linoleic acid and linolenic acid decreased obviously. When fried for 30 h trans acid content of soybean oil, sunflower oil, rice bran oil, corn oil, palm oil increased from 0.57%, 0.45%, 2.53%, 0.67%, 0.12% to 2.53%, 1.51%, 4.00%, 3.61%, 4.00%. The dosage were 1.96%, 1.06%, 1.47%, 2.94%, 1.47% respectively.(2)The polar components content were analysised by CAMAG thin layer chromatograph in frying oil. Having taken the separated and purificated polar components and fried oil of having known polar components content as the internal standard substances. The determing results of two determing methods were compared with the method of national standard column chromatography. verifying the method thin layer chromatography(TLC) was based on testing to different types and different levels of fried vegetable oil repeatability. Research results showed that the polar components content of frying oil werw determined by thin layer chromatography have a good correlation with absorption peak area. The correlation coefficient could reach to 0.9 above.In order to further judging the accuracy of the two methods, repetitive verification test were proceed.Among that when taking the separated and purificated polar components as the internal standard substance, 21 sample were measured randomly, measurement deviation of 6 samples were less than 2%, measurement deviation of 10 samples were between 2% and 4%, measurement deviation of 4 sample were between 4% and 6%, measurement deviation of only 1 sample was 6.05% higher than 6%. when taking fried oil of having known polar components content as the internal standard substance, 33 samples were measured, measurement deviation of 13 samples were less than 2%, measurement deviation of 4 samples were between 2% and 4%, measurement deviation of 5 sample were between 4% and 6%, measurement deviation of 11 sample were higher than 6%. So the thin layer chromatography(TLC) could be used as a new kind of rapid detection method to determing the polar components content of oils and fats.(3)On the basis of building the method of determining total polar components by thin layer chromatography in frying oil, the volatile components of fried vegetable oil were analyzed by solid phase mi- croextraction and gas chromatography-mass spectrometry. Volatile components of fried vegetable oil and not fried vegetable oil were analyzed under the condition that the extraction temperature was 70 ℃, the balance time was 30 minutes, parse time was 4 minutes. The results showed that compared with not fried vegetable oils, fried vegetable oils contained a large amount of volatile components, Different kinds of fried vegetable oils contained the same volatile components roughly, One kind of Vegetable oil has been fried for different time volatile composition is slightly different, volatile components is roughly same at the beginning of the frying process, but a small molecules of fatty acids began to produce in the later period of the frying process. The major different volatile components between fried vegetable oils and not fried vegetable oils were(E)-Hept-2-enal,2-Hexenal, 1-Octen-3-ol; 2-Pentylfuran,(2E,4E)-Hepta-2,4-dienal, caproic acid, Heptanoic acid,(E)-2-Octenal, 3,5-octadienone, 3,5-octadien-2-one, 1-Nonana,(2E)-2-Nonenal,(E,E)-2,4-Nonadienal, trans-2-Decenal,(E,E)-2,4-Decadien-1-al, 2-Undecenal, Tetradecane and Hexadecane. Among above the most typical volatile component was(E,E)-2,4-Decadien-1-al,which accounted for more than 20% of total volatile components.(4)On the basis of building the method of determining total polar components by thin layer chromatography in frying oil, firstly having separated the polar and nonpolar components by using normal phase silica gel preparation medium-pressure type rapid purification liquid chromatographic. the non-volatile polarity components were separated by efficient size exclusion chromatography. And then determined by refractive index detector, The nature was determined by the relative molecular mass – polystyrene, and the contend was quantitated by peak area normalization method. After the polarity components were analysised by chromatographic, three non-volatile polarity components were separateed out, named oxidized triglycerides polymers, oxidized triglycerides oligomers, oxidized triglycerides monomer. The analysising results showed that, when the sunflower seed oil was fried for 30 h under the condition 190 ℃, oxidized triglycerides polymer content reached to 28.1%, oxidized triglycerides monomer content reached to 9.1%. Oxidized triglycerides polymer content reached to 28.1%, oxidized triglycerides monomer content reached to 9.1%.in purified polar components... |
