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He W.-X.,Minjiang University | Hong G.-S.,Fujian Provincial Administration for Industry and Commerce | Fang R.,Minjiang University | Cai X.-C.,Fujian Provincial Administration for Industry and Commerce | Huang S.,Fujian Provincial Administration for Industry and Commerce
Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis | Year: 2015

In the present study, by measuring the A3005 (representing unsaturation), A985 (representing conjugated fatty acids), A960+A985 (representing trans-fatty acid ) of southern common vegetable oils (peanut oil, corn oil, canola oil, soybean oil, sunflower oil, tea seed oil and olive oil), "waste oil" and overdue vegetable oils, the pass-setting-range of these three index values for the vegetable oils was obtained. On this basis, a method for rapid screening unqualified vegetable oil (expired, adding low-cost oil, adding "waste oil") was established. The method effectively improved the monitoring efficiency of vegetable oil. With this method of screening a number of suspected substandard oils were proved unqualified by determination of fatty acid composition and 11, 12, 13, 17 fatty acid content. Through the combination of several detection methods, the causes for disqualification of vegetable oils can be further inferred. ©, 2015, Science Press. All right reserved. Source


He W.-X.,Minjiang University | Hong G.-S.,Fujian Provincial Administration for Industry and Commerce | Fang R.,Minjiang University | Cai X.-C.,Fujian Provincial Administration for Industry and Commerce | Huang S.,Fujian Provincial Administration for Industry and Commerce
Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis | Year: 2015

Because both refined "waste oil" and the third category "waste oil" known as frying old oil experience a longer history at temperature higher than 200 ℃ compared to the vegetable oil. In this study, the relative change rates of content of conjugated fatty acid glycerides, content of tans-fatty acid glycerides and unsaturation were investigated after being at high temperature for several hours by using FTIR-ATR in order to find out specific targets for "waste oil". The results show that (1) Starting from 160 ℃, the contents of conjugated fatty acids glycerides and trans-fatty acid glycerids in the vegetable oils increase but unsaturation decreases with heating temperature and heating time increasing. (2) When heating temperature reaches 200 ℃ or more, the heating time up to four hours or longer, the three indicators(conjugated fatty glycerids, trans-fatty acid glycerids and unsaturation) of six kinds of vegetable oils have substantial changes. (3) The content of linoleic acid in the vegetable oil has some contributions to the change amplitude of contents of conjugated fatty acid glycerides, and the content of oleic acid in the vegetable oil has some contributions to the change amplitude of content of trans-fatty acid glycerides. (4) In addition, during the warranty period change amplitudes of three indicators are relative small compared with the case of after being at high temperature for several hours. Unsaturation decrease and content of conjugated fatty acid glycerides increase with storage-time increasing. However, unlike the case of after being at high temperature for several hours, the content of trans-fatty acid glycerids decreases with storage-time increasing. Experimental results show that three index value and its variation can be used as specific indicators for refined "waste oil" and "waste oil". ©, 2015, Science Press. All right reserved. Source

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