Detecting And Indentifying The Volatile Component Of Waste Oils

In recent years, many illegal traders sell waste oil to make money, resulting in a large part of the waste oil return to our dining table after processing and refining. The waste oil seriously endanger people’s health, because of its containing the heavy metal elements, aflatoxin B1 and benzo(α) and other toxic substances which exceeding the standard. To prevent waste oil into the catering services link and effective protect the food safety of consumers, an urgent need is to establish the related laws and regulations of the waste oil, and the most important key is to establish the method of pretreatment and detection of illegal cooking oil.Because the source of the waste oil is extensive, the chemical structure is complex, and criminals are mostly to sales of waste oil refining after incorporation of qualified edible oil, the waste oil is more difficult to detect. By now there are no authority authoritative detection method. The existing detection methods are not targeted, and some can only detect a single source of waste oil; some lack of sensitivity, cannot be detected after refining waste oil, or can not detect the incorporation of small amount of cooking oil. After research efforts over the past few years, at present mainly mature methods are as following: physicochemical method, the material characteristics method, thin layer chromatography, spectrometry, high performance liquid chromatography, nuclear magnetic resonance spectroscopy, microscopy and specific gene detection.In this thesis, we firstly optimized pretreatment method of the waste oil, and further identified the main group of waste oil and analyze its reaction principle by using gas chromatography- mass spectrometry. And we detected 40 batches of illegal cooking oil samples in the market using above methods, and detect and analyze the related parameters of GB 2760-2005 “Hygienic standard of edible vegetable oil” as a contrast experiment, the main conclusions are as follows:1. Through the comparison of two kinds of waste oil pretreatment method which are simultaneous distillation extraction method and evaporation of water-vapor of organic solvent extraction method, we found that effect of the fist method is better, the TIC ion analysis exhibit the good choice of separating degree and more peak fractions. By comparing three kinds of extracting reagent diethyl ether, petroleum ether, hexane, we found that diethyl ether have the best effect, which shows good separation effect and high value of the response. At the same time, we also optimized the optimum adding amount of pretreatment and the best time of distillation.2. By using gas chromatography-mass spectrometry, we further separated and identified the sample components. And we found that the waste oil contains a large number of aldehydes, alcohols, hydrocarbons, acids, esters and other substances, and the degree of oxidation of the oil is bad, the content of these substances is bigger, the experimental results provide some reference to the waste oil detection screening. From the analysis of lipid oxidation in principle, hexanal, pentanal, nonanal, octanal, heptyl aldehyde, 2-pentyl furan is an important drop product of oleic acid and linoleic acid.(E)-2-heptenal, 2, 4-nonadienal, anti-2,4-decadienal was produced in the process of oil rancidity, and the principle of producing is analyzed.3. In this thesis, we chose more representative of the 40 batch of waste oil products, of which 10 batches are representative of 10 batches of hogwash oil for deep frying oil represents, in addition the 20 batch of suspected “drainage oil” products. Detection by gas chromatography-mass spectrometry, four types of sources of this experiment selected, barbecue stall waste oil is not qualified rate is highest, the characteristic volatile compounds by the representative of the frying oil for trans olefinic aldehydes, snacks, such as Hot pot food waste by the representative of the hogwash oil will appear caffeine and other foreign substances, while the market, farmers, small workshops oil did not find the characteristic volatile substances. Through the above experimental and the detection results of the acid value and peroxide value of standard “GB 2716-2005 Hygienic standard of edible vegetable oil”, we found that although the above criteria cannot be used as a method to determine the illegal cooking oil detection method, but can be as drainage oil detection screening.This paper provides a practical and reasonable, simple and executable pretreatment methods and conditions, gas chromatography-mass spectrometry conditions of “illegal cooking oil”. By analyzing a large number of experimental data, we obtained the relatively reliable results, and provides a certain reference for determining the “illegal cooking oil”.