Study On Rapid Analysis Method Of Fatty Acids In Oil Crops

Fatty acid in oil crops was an important index to determine the quality of vegetable oils,its composition and content determine the nutritional value of vegetable oils to a certain extent.In the process of fatty acid analysis,lipid extraction and methylated derivatization were the two most important pre-treatment steps,made a direct impact on the qualitative and quantitative analysis of fatty acids.In this paper,the methods of lipid extraction and methylated derivatization of oil crops were optimized and improved,and the composition of fatty acids in oil crops was quantitatively analyzed by GC-MS.The purpose of this study was to establish a set of accurate,rapid and efficient fatty acid analysis methods,and to provide a solid theoretical basis for lipid pretreatment methods and fatty acid analysis of oil crops.In this paper,the dry column method was used to extract oil from oil crops.Using nhexane as eluting solvent,the amount of proppant sodium sulfate and diatomaceous earth was4 g,the mass ratio of sodium sulfate and diatomaceous earth was 2:2,and the amount of nhexane was 40 m L.In these conditions,the extraction rate of walnut oil reached 60.68%.At the same time,dry column method was compared with Soxhlet extraction method and Folch method,the results showed that there was no significant difference in the extraction rate of the three methods(P>0.05).The dry column method could simplify the operation process and achieve one-step extraction,separation and purification while ensuring the extraction rate.At the same time,it also reduced the use of organic solvents,especially the used of n-hexane instead of chloroform,methanol and other toxic solvents as eluent solvent,reducing the harm of the it experiment to human and environment,so it was a simplie,safe and efficient method of oil extraction.Trimethyl sulfur hydroxide method(TMSH)was used as the derivatization method.Added 40 ?L of methyl butyl ether into 1 mg of oil,shake for solubilization,and then added40 ?L trimethyl sulfur hydroxide solution(TMSH,0.2 mol/L of methanol solution),shake for reactiong at room temperature,and the complete methylation reaction can be achived.This method had a wide range of applicability.At the same time,it had the advantage of less side reactions in the derivation process,no isomerization of unsaturated fatty acids,and widely applicable method of methyl esterification derivation.The fatty acid composition of six oil crops was analyzed by GC-MS.The saturated fatty acids(SFA)of six oil crops are mainly palmitic acid(C16:0)and stearic acid(C18:0),the content of saturated fatty acids in soybean and peanut oil was 16.74% and 16.47%,respectively;The monounsaturated fatty acids(MUFA)are mainly oleic acid(C18:1n-9),and the content of monounsaturated fatty acids in tea seed oil is up to 80%;The Polyunsaturated fatty acids(PUFA)are mainly linoleic acid(C18:2n-6)and ?-linolenic acid(C18:3n-3).In addition to the lowest polyunsaturated fatty acids in tea oil seed oil,other oil crops were rich in polyunsaturated fatty acids.The highest content of polyunsaturated fatty acids in walnut oil was 74.82%.At the same,cluster analysis of six oil crops was carried out by fatty acids,we could divide six kinds of oil crops into three categories,tea oil seed was the first category,its fatty acid was mainly oleic acid,the content is as high as 79.42%;The content of linoleic acid was only 9.10%.Walnut and soybean were the second largest group,and their fatty acids were mainly linoleic acid and oleic acid,and the content of linoleic acid was much higher than oleic acid,among which linoleic acid was 63.45% and 54.01%,oleic acid was only14.44% and 19.86%,respectively;Sesame,sunflower seed and peanut were the third largest group.The fatty acids of the three groups were mainly oleic acid and linoleic acid,but the contents of the two fatty acids were relatively close,among which oleic acid is 40.09%,34.07% and 52.04%,linoleic acid is 43.92%,54.91% and 30.48%,respectively.The proportion of fatty acids in different oil crops was quite different,the ratio of SFA/MUFA/PUFA ranges from 1:1.20?7.50:0.88?7.15,it showed that the fatty acid composition of six oil crops was not reasonable.The ratio of SFA/MUFA/PUFA could not reach the ratio of 1:1:1 recommended by Chinese Nutrition Society.The n-3/n-6 ratios of walnut and soybean oil were 0.18 and 0.17 respectively,which were close to the dietary ratios recommended by the International Food and Agriculture Organization(FAO)and the World Health Organization(WHO),the content of n-3 series polyunsaturated fatty acids in the other four oil crops was low or does not contain n-3 series polyunsaturated fatty acids.It also showed that the ratio of SFA/MUFA/PUFA and n-3/n-6 of single vegetable oil did not meet the requirement of balanced dietary fatty acid ratio.At the same time,the atherogenic index(AI)and thrombogenic index(TI)of fatty acids in six oil crops were far lower than those in beef,pork and mutton(AI 0.60,0.72 and 1.00,TI 1.37,1.06 and 1.58 respectively),indicating that six oil crops played an important role in reducing blood fat,softening blood vessels and preventing cardiovascular diseases.