The Research Of Methods To Detect Characteristic Components In Kitchen Waste Oil

Hogwash oil is producted by kitchen waste oil（such as hotpot oil, frying oil） after simplyprocessing and refined. In recent years, with the rapid development of society and economy,as well as the growing demand for edible oils, some lawless people have taken advantage ofthose kitchen waste oil to product hogwash oil in large quantities. The problem of hogwashoil backing on the table has been a growing trend. At present, many refined hogwash oil hasbeen able to fully meet the national hygienic standard of edible vegetable oil and the study ofhogwash oil on detection and identification work is still at an early stage. This study is basedon hogwash oil sources and the change in edible oil, trying to find specific targets which candistinguish hogwash oil and edible vegetable oil well.Determination of cholesterol content: The condition of saponification and extractionsolvents are main factors of cholesterol extraction in edible oils. In order to get the maximalextraction content of cholesterol in oil, the effect of different extraction solvents,saponification temperature, saponification time and consistency of KOH-C₂H₅OH werediscussed to optimize the cholesterol extraction condition with the response surfacemethodology. Then we got the optimal conditions as follows: the extraction solvents isN-hexane, the extraction temperature is67℃, the extraction time is60min, the consistency ofKOH-C₂H₅OH is0.9mol/L. We determined the cholesterol contents in different kinds ofedible oils. From the experimental results can be seen, the cholesterol contents in kitchenwaste oils and edible oils are very different, so cholesterol contents can be used as a specificdiscriminate target for the work of identification of hogwash oils and edible vegetable oils.Analysis of fatty acid composition: Using gas chromatography-mass spectrometrydetermined fatty acids in oils after methyl esterification. We can seen that fatty acidcomposition in edible vegetable oils is relatively stable, while hogwash oils, hotpot oils andfrying oils is unstable by comparison. From the result, we also find the emergence of transfatty acid and higher contents of myristic acid in hogwash oils.Analysis of volatile substances: Headspace solid phase micro-extraction-gaschromatography-mass spectrometry in analysis of volatile oils have a convenient, efficient,and high sensitivity advantage. Using this method we determined volatile substances fromedible vegetable oils（canola oil, peanut oil, corn oil）, hotpot oils, frying oils and hogwash oils.From the results of analysis, we can see that every type of qualified edible vegetable oil hasits unique and stable odorousconstituents. Free fatty acids, trans-2-4-decadience aldehyde andanethol impurities are basis of identification of hogwash oil and qualitied edible oils.