【作者】 王凯；

【导师】 王亚林；

【作者基本信息】 上海交通大学 ， 环境工程， 2016， 硕士

【摘要】 本文通过活性炭纤维-固相微萃取技术(ACF-SPME)与气相色谱/飞行时间质谱(GC/TOFMS)联用,检测了植物油、动物油和地沟油。1)通过萃取条件的优化,确定了最佳萃取条件:120℃油浴,油品取样量:0.1000g,Na2SO4用量:0.0100g,顶空萃取时间:50min。按照优化条件对花生油、大豆油、葵花籽油、橄榄油、玉米油、芝麻油进行检测,共检测出70-80种物质。不同油品挥发性物质组成接近,都含有脂肪酸类、醛类、酮类以及脂类等有机物;其中用该萃取方法可检出六种挥发性脂肪酸:戊酸、己酸、辛酸、壬酸、棕榈酸、硬脂酸。2)通过固定油量对同一油样不同萃取次数对萃取结果影响的实验,证明了萃取次数不会影响萃取结果的稳定性。3)不同活化批次的活性炭纤维对萃取影响的实验结果表明,不同批次制备的活性炭纤维存在吸附差异性,对脂肪酸的绝对吸附量不同,但是结构相似的脂肪酸相对面积保持不变,证明活性炭纤维对脂肪酸是竞争性等比例吸附。与商业ACF纤维进行对比后发现,自制活性炭纤维对于脂肪酸的萃取效果更灵敏,吸附量更大。4)不同品牌食用油的实验,对市面上几个品牌的植物油进行了检测,发现挥发性脂肪酸相对含量不受品牌的影响,消除了不同品牌的差异性误差。5)通过检测不同来源的地沟油和不同种类的动物油发现,地沟油中含有70-80种物质,与植物油组分相似;动物油中检出的挥发性物质较少。通过比较地沟油与食用油中挥发性脂肪酸的含量变化,确定了新的A值指标法。A值=棕榈酸的峰面积/己酸的峰面积:地沟油的A值大于0.8,而植物油的A值均小于0.8。以0.8为界,可以很好地区分出地沟油和植物油。6)多次烹饪加热植物油的实验发现,食用油中棕榈酸的含量会随着食用油模拟烹饪次数的增加而增加,A值指标也存在增加趋势,证明了A值能够反映油品的氧化程度,可以作为区分煎炸老油和植物油的指标。使用SPSS软件对不同油品进行判别分析,证明了A值指标的区分度较好。7)通过地沟油与植物油的掺杂实验,推导出关于A值的掺杂曲线,符合实测值规律。该曲线是以A值作为检测值的线性曲线,能够很好地检测出掺杂油品的掺杂比例,为地沟油的检测提供了有力的支持。根据掺杂曲线和烹饪规律,构造出烹饪-掺杂曲线:对于未知油品,测定其初始A值以及加热5次后A值。如果检测样品加热5次后A值依然位于烹饪曲线上,则说明该油品中氧化程度一致,未经过掺杂,可根据A值指标进行使用次数的判定;如果检测样品加热5次后A值不在烹饪曲线上,则说明该油品中物质的氧化程度不一致,为掺杂油品,可通过掺杂曲线进行判定掺杂比例。8)通过不同调和油的实验,发现原始植物油与调和油的A值基本保持不变,在误差范围内,说明A值指标不能有效区分出调和油。9)辣椒油的检测实验确定了烃类物质的存在,辣椒中检测出物质多以饱和烃类为主。而在食用油中,基本不含有饱和烃类物质,烯烃、炔烃较多。以饱和烃、不饱和烃类作为辅助检测地沟油的指标,为A值的检测结果提供支持。通过以上实验,本文初步确定了利用挥发性脂肪酸鉴别地沟油的新方法,确定了A值指标,为地沟油检测提供了新的思路。更多还原

【Abstract】 In this paper,active carbon fiber-solid phase microextraction(ACFSPME)and gas chromatography / time-of-flight mass spectrometry(GC/TOFMS)were used to detect the vegetable oil,animal oil and waste cooking oil.1)Through the experiment of the extraction conditions,the optimum extraction conditions were determined: 120℃ for oil bath,oil sampling 0.1000 g,Na2SO4 0.0100 g,extraction time 50 min.According to the optimized conditions,70-80 species were detected in the peanut oil,soybean oil,sunflower seed oil,olive oil,sesame oil.The volatile compositions of different oil were fatty acids,aldehydes,ketones,lipids and other organic compounds.There were six kinds of volatile fatty acid detected in all oils: valeric acid,caproic acid,octanoic acid,nonanoic acid,palmitic acid,stearic acid.2)The experiment of different extraction times of the same oil sample by the fixed oil amount shows that the extraction times will not affect the stability of the results.The extraction times should be controlled under 4 times.3)The experiment of different activated carbon fibers were found that activated carbon fibers have different adsorption,but the relative content of the fatty acids remained unchanged.Compared with the commercial activated carbon fibers,it was found that the homemade fibers were more sensitive to the extraction of fatty acids and the adsorption capacity was more.4)Different edible oil of several brands in the market was detected and the relative content of volatile fatty acids was not affected by the brand.5)By detecting waste cooking oil of different sources and animal oil of different kinds,the results show that waste cooking oil contains 70-80 species,which is similar to that of vegetable oil.By comparing the contents of volatile fatty acids in the waste oil and edible oil,the new A value method was determined.The A value = the peak area of palmitic acid / peak area of caproic acid: the A value of drainage oil was more than 0.8 and the A value of vegetable oil was less than 0.8.The A value 0.8 as the boundary can be a good area to separate the waste cooking oil and vegetable oil.6)Through the experiment of cooking vegetable oil,the results shows that the content of palmitic acid in edible oil will increase with increasing cooking numbers of edible oil,there is an increasing trend of A value.This experiment proved that A value can reflect the oxidation degree of edible oil.It can be used to distinguish the fried oil and vegetable oil.Then SPSS software was used to analyze different oil to prove the sensitivity of A value.The result shows that A value is sensitive to distinguish edible oil and waste cooking oil.7)By the experiment of mixing waste cooking oil with vegetable oil,the doped curve of A value is deduced,which accords with the regularity of the measured value.The curve is a linear curve,which can be used to detect the proportion of the doped products.It provides a powerful support for the detection of waste cooking oil.According to the doped curve and the cooking regularity,the cooking-doped curves are constructed.Through detecting the A value of 5 times heating of the unknown oil,we will know the oil is used oil or doped oil.If the A value is still located in the cooking curve,the oxidation degree of the product is consistent with edible oil.If the A value is not in the cooking curve,it may be the mixture of waste cooking oil and vegetable oil.8)By the experiment of mixing different edible oil,the A value of the original vegetable oil and blend oil both remained unchanged and the A value is not effective in the error range.It shows that the blend oil can’t be detected by the method of A value.9)The detection experiment of pepper oil shows the existence of hydrocarbon substances and most of the materials were saturated hydrocarbons such as tridecane.While in the edible oil,hydrocarbons can’t be found in the basic materials except alkenes and alkynes.The result can be used to detect the waste cooking oil as an auxiliary test.It will provide support for the method of A value.Through the above experiments,this paper preliminarily determined the new method of using volatile fatty acids in the identification of waste cooking oil and A value calculation formula is determined.This paper provided a new way for the detection of the waste cooking oil.更多还原