A micro-method for the estimation of oil content and fatty acid composition in seeds with special reference to cyclopropenoic acids

A micro-method is described for the routine estimation of oil content and fatty acid composition in seeds containing cyclopropenoic fatty acids (CPEFA) by determination of the total and component long-chain fatty acids. The oil was transmethylated without prior extraction using 1.17% sodium methoxide in methanol at 80°C for 45 min. The resultant fatty acid methyl esters were separated and measured by gas-liquid chromatography using a glass capillary column coated with Carbowax 20 M at 170°C. The method was shown to be applicable to a wide range of seeds including cottonseed (Gossypium hirsutum), kapok (Ceiba pentandra), paka (Urena lobata), baobab (Adansonia grandidieri and A. suarezensis). Individual seeds can be used with this method which needs only 50 to 150 mg for analysis. Results obtained with this micro-method were reproducible and good recoveries of oil and individual fatty acids were observed. The micro-method was compared for the determination of CPEFA (malvalic plus sterculic acids) to the nuclear magnetic resonance quantitation and gas-liquid chromography after derivatisation of CPEFA in more stable compounds.     

高温气相色谱分析油脂转酯反应

建立了高温气相色谱分析油脂转酯反应样品中各种脂肪酸甲酯和脂肪酸甘油酯的方法。样品经硅烷化处理后分流进样,使用VF-5HT高温毛细柱,优化后的程序升温使各种脂肪酸甲酯和甘油酯得到良好分离,同时缩短了分析时间;十三酸甲酯和辛酸三甘油酯双内标分别对脂肪酸甲酯和脂肪酸甘油酯定量,提高了分析的准确度。该方法为油脂转酯反应制备生物柴油提供了分析依据。     

食用植物油脂肪酸的高分辨气相色谱分析

提出用一种经过改进的方法制备食用植物油的脂肪酸甲酯衍生物，并利用高分辨率毛细管柱分析其中脂肪酸的组成和含量。在确定的气相色谱操作条件下，所用的毛细管柱不仅能够测定食用植物油中的主要成分，而且可测得花生油中含量低至10mg／L数量级的痕量芥酸成分。     

Effects of Heat and Hydrogenation on Cyclopropenoid Fatty Acid Composition of Baobab (Adansonia Suarezensis) Seed Oil

The seeds of the baobab Adansonia suarenzensis (Bombacaceae) contain 46.2% oil used for cooking by the malagasy population. This oil gives a positive Halphen test showing the presence of cyclopropenoic fatty acids (CPEFA). Composition analysis of derivatized fatty acid methyl esters was done by gas-liquid chromatography (GLC). The A. suarenzensis seed oil contains mainly palmitic (46%) stearic (3.5%) oleic (21%) and linolenic (12%) acids. Effect of heat on CPEFA content of boabab oil was studied at 133°C and 180°C. Major decomposition of CPEFA at 180°C shows that deodorisation would be the main step in the oil refining process. Hydrogenation of the baobab oil using an industrial hydrogenating catalyst results in CPEFA content decreasing rapidly.     

基于特征脂肪酸的食用油中棉籽油掺假鉴别技术

目的 开发检测棉籽油特征标志物锦葵酸和苹婆酸的气相色谱-质谱法,实现食用油中棉籽油掺假确证性鉴别。方法 利用碱式甲酯化方法对油脂样品进行酯化,正己烷提取脂肪酸甲酯,加入无水硫酸钠过滤,选择性离子扫描模式采集数据,外标法定量,以特征标志物判定食用油中是否掺假棉籽油。结果 建立的食用油中锦葵酸和苹婆酸高灵敏检测技术能准确鉴定食用油中5%棉籽油掺假。与基于脂肪酸组成结合偏最小二乘法-判别分析仅能鉴别大豆油中10%以上的棉籽油掺假相比,本研究建立的基于标志物方法鉴别灵敏度更高。结论 本研究建立了食用油中苹婆酸和锦葵酸高灵敏检测技术,为鉴别食用油中棉籽油掺假提供了关键检测技术支撑。     

DIRECT DETERMINATION OF TRANS-OCTADECENOIC ACID IN DIET COMPOSITES USING A COMBINATION OF SILVER ION-HIGH PERFORMANCE LIQUID CHROMATOGRAPHY AND CAPILLARY GAS CHROMATOGRAPHY

Silver ion-high performance liquid chromatography (Ag-HPLC) and capillary gas chromatography (GC) were combined to quantify total trans -octadecenoic acid (18:1t) in diet composites and oils. The 18:1 cis and trans fatty acid methyl esters (FAME) of saponified and methylated (BF₃/methanol) oils and food composite total lipid extracts were separated by Ag-HPLC (ChromSpher5 Lipids column); total 18:1t in the trans fraction was quantified by GC (105m × 0.25mm SP-2560 capillary column). Positional isomers 18:1c and 18:1t which coeluted in direct GC were clearly separated by preparatory Ag-HPLC. Quantitative recovery of 18:1t from a standard mixture of FAME, an oil, and a diet composite was obtained for additions of 4–57 mg. The analytical range for total 18:1t was 1.6–260 mg/mL per aliquot of total lipid extract or oil. Relative standard deviations were < 6% for food composites and < 3% for oils and pure standards.     

棉籽油脂肪酸甲酯化的方法及其脂肪酸含量分析

以新陆早39号以及新陆早50号的棉籽为材料,利用索氏提取仪提取其总油脂,分别采用三种常用的脂肪酸甲酯化方法:KOH-甲醇法,H₂SO₄-甲醇,14% BF₃-甲醇法进行甲酯化后,GC-MS上机分析;通过37种脂肪酸甲酯混标制定标准曲线,用外标法进行定量。结果表明:KOH-甲醇法甲酯化的脂肪酸GC-MS上机分析能检测到10种脂肪酸组分;H₂SO₄-甲醇与14% BF₃-甲醇法只能检测到6种。用KOH-甲醇法甲酯化后GC-MS测定表明,棉籽油脂肪酸以多不饱和脂肪酸的亚油酸为主,其次是饱和脂肪酸的棕榈酸以及单不饱和脂肪酸的油酸。在新陆早39号以及新陆早50号中,每克棉籽中亚油酸的含量分别达147.29 mg与163.2 mg,分别占其油脂含量的60.12%与60.83%;棕榈酸含量分别为65.05 mg与62.28 mg,分别占其油脂含量的26.55%与23.24%。油酸含量分别为24.79 mg与22.19 mg,分别占其油脂含量的10.12%和8.28%。结论:三种常用的脂肪酸甲酯化方法中,KOH-甲醇法更方便,快速,检测种类多,适用于棉籽脂肪酸的甲酯化。     

应用脂肪酸甲酯快速筛选植物油中掺假地沟油

根据植物油和地沟油中脂肪酸酯存在方式的不同,建立植物油中地沟油掺假的快速筛选方法。植物油中脂肪酸是以甘油三酯的形式存在,地沟油中脂肪酸以脂肪酸甲酯的形式存在,利用气相色谱-质谱的全扫描模式,结合NIST 05标准谱库检索功能,对37 种脂肪酸甲酯进行测定。样品采用直接稀释-气相色谱-质谱全扫描分析脂肪酸甲酯,100 个植物油样品中均未检出脂肪酸甲酯;20 个地沟油样品中13 个检出肉豆蔻酸甲酯（C14∶0）、棕榈酸甲酯（C16∶0）和硬脂酸甲酯（C18∶0）等14 种脂肪酸甲酯,检出率为65%,且70%的检出脂肪酸甲酯的地沟油样品中脂肪酸甲酯种类多、含量较高。因此,若植物油样品脂肪酸甲酯种类多、含量高,则可判定为有地沟油掺假;若脂肪酸甲酯含量低或没有脂肪酸甲酯,则可以进一步用其他指标和方法进行检测,脂肪酸甲酯的检测方法可以作为地沟油掺假的快速粗筛方法。     

Optimization of the GC method for routine analysis of the fatty acid profile in several food samples

The fatty acids profile of food samples was determined by gas chromatography (GC). The fat was extracted from different food samples using Soxhlet technique. Extracted triglycerides were converted to corresponding methyl esters using methanolic solution of potassium hydroxide (trans-esterification). GC method for the analysis of obtained methyl esters was optimized on two different cyanopropyl capillary columns. Good resolution of all fatty acids commonly found in foodstuffs was achieved. After optimization, the method was validated and the results for linearity, precision, limit of quantitation (LOQ), limit of detection (LOD), robustness and stability were presented. The method has been applied to the quantitative determination of the fatty acid content in different food samples: edible oil, dairy products rich with omega-3 fatty acids, different food supplements, baby food, etc.     

6种食用植物油及其生物柴油中脂肪酸成分的比较研究

采用毛细管气相色谱法，以氢火焰为检测器，测定了菜籽油、花生油、玉米油、棉籽油、芝麻油和大豆油及其相应生物柴油中脂肪酸的组成。比较发现，植物油及其生物柴油中脂肪酸组成基本一致。因此，可以通过测定植物油中脂肪酸的组成来预测生物柴油中脂肪酸甲酯的分布。     

菜籽生物柴油合成反应程度的气相色谱法判断

以十三酸甲酯为内标,建立了菜籽生物柴油中主要脂肪酸甲酯的气相色谱测定法。进样中各脂肪酸甲酯含量在各自线性范围内的线性相关系数r≥0.9963、平均回收率在97.59%~101.42%、相对标准偏差在1.32%~2.89%。通过测定反应试样中的脂肪酸甲酯总量,再与原料油脂完全甲酯化产品中的甲酯总量相比较,可以准确地判断生物柴油合成反应程度。     

A survey of lipid composition of Khoa samples in relation to possible adulteration

The fatty acid composition of Khoa a heat‐desiccated milk product was determined and compared with those obtained with cow milk, buffalo milk and toned milk. Fatty acid methyl esters were analysed by capillary gas chromatography (GC). Among the Khoa samples analysed, 57% showed fatty acid composition characteristic of milk fat. The ratio of major saturated fatty acids to unsaturated fatty acids (S/U) including 18:1 transfatty acids was calculated for all the fats. The GC profiles of 43% Khoa samples showed the composition of fatty acids not conforming to milk fats. The Khoa samples adulterated with nonmilk fats were further confirmed by cholesterol and triglyceride estimation.     

油脂酯交换过程中甘三酯Sn-2位脂肪酸组成分析方法的改进研究

在油脂酯交换反应过程中，产物油脂往往需要进行Sn-2位脂肪酸组成的鉴别与分析，由于反应生成物（如脂肪酸，脂肪酸甲酸，甘三酯，甘一酯，甘二酯等）的性质十分相似，要研究酯交换过程中甘三酯的Sn-2位脂肪酸组成，所需要甘三酯的量往往需要很多块TLC板的分离才能实现，致使实验费用增加，效率降低，本文主要研究了脂肪酸，脂肪酸甲酯以及硅胶对油脂Sn－2位脂肪酸的影响。实验结果证明：脂肪酸、脂肪酸甲酸以及硅胶在一定的条件下不影响油脂Sn－2位脂肪酸组成分析的结果，这种方法是对国际纯粹化学和应用化学联合会（IUPAC）方法的改进和补充，大大简化了分析过程，可以广泛地应用于相关的研究与分析中。     

气相色谱-质谱法测定东盟进口小食品中的 反式脂肪酸

目的建立气相色谱-质谱法检测东盟进口小食品中反式脂肪酸的分析方法。方法样品经油脂的提取、甲酯衍生化,在气相色谱中采用安捷伦CP-Sil 88 for FAME毛细管色谱柱进行分析,质谱分析采用全扫描模式。对柱长、载气流速和和柱温进行了优化,采用优化后的条件对样品进行测定。结果反-9-十八碳烯酸甲酯和反-9,12-十八碳二烯酸甲酯标准品在10~80 mg/L范围内线性关系良好,r~2分别为0.9989和0.9985,方法的检出限(limit of detection,LOD)和定量限(limit of quantification,LOQ)分别为0.4 mg/L和1.0 mg/L。2种物质在3个添加水平的平均回收率为90.5%~105.6%,相对标准偏差为3.5%~8.2%。样品中反-9-十八碳烯酸甲酯和反-9,12-十八碳二烯酸甲酯的分离度好。结论该方法准确度和精密度良好,分离效果好,可以用于对东盟小食品中反式脂肪酸的检测。     

基于植物油中脂肪酸烷基酯含量变化鉴别废弃油脂

采用固相萃取柱净化,气相色谱-质谱联用法测定了6种植物油中脂肪酸烷基酯(包括脂肪酸甲酯和脂肪酸乙酯)的含量,并研究其在植物油煎炸、废弃及废弃油脂精炼等环节中的变化。结果发现,6种植物油中脂肪酸烷基酯的含量均低于30 mg/kg,而植物油在废弃过程中可能会形成大量脂肪酸乙酯,生成量与油脂是否烹饪及废弃物中乙醇含量有关。脂肪酸烷基酯在脱色工艺中不能被去除,但在脱臭中可被去除。因此,可以通过测定植物油中脂肪酸烷基酯含量发现废弃油脂,为废弃油脂的鉴别工作提供新的思路。     

竹柏种仁油脂成分及其抗氧化活性分析

采用5种方法对竹柏种仁油脂进行提取,并通过核磁共振和气相色谱-质谱技术分别对其油脂成分和脂肪酸组成进行分析,同时采用DPPH自由基清除法和羟基自由基清除法对竹柏种仁油脂的抗氧化活性进行研究。结果表明,5种方法对竹柏种仁油脂的提取率存在显著差异(P 0.05),其中Folch法的提取率最高,为53. 81%。竹柏种仁油脂以甘油三酯为主,磷脂、游离脂肪酸和甾醇含量极低。竹柏种仁油脂经2 mol/L KOH-甲醇溶液室温衍生3 min,甲酯转化率即达99. 80%;且其脂肪酸以油酸(18. 65%)、亚油酸(43.49%)和花生烯酸(30.65%)为主,不饱和脂肪酸含量高达90%以上。竹柏种仁油脂对DPPH自由基和羟基自由基的IC_(50)分别为3.36 mg/mL和0. 38 mg/mL,表明竹柏种仁油脂具有较好的抗氧化能力,可作为健康植物油脂进行开发利用,具有良好的开发潜力和应用前景。本研究为竹柏种仁油脂的提取、成分分析和抗氧化活性研究提供了一定的参考。     

3种海洋鱼油脂肪酸组成及其位置分布

采用米黑根毛霉源固定化脂肪酶(Lipozyme RM IM)对常见的海洋鱼油甘三脂进行水解,分析了凤尾鱼、金枪鱼、三文鱼甘三酯中脂肪酸的组成及位置分布。采用硅胶色谱柱分离3种海洋鱼油甘三脂,利用Lipozyme RM IM的sn-1,3特异性,将酯化在sn-1,3位上的脂肪酸(EFA)水解成游离脂肪酸(FFA),然后通过薄层层析(TLC)分离得到sn-2-单甘酯,再甲酯化后利用气相色谱(GC)测定sn-2位脂肪酸组成,并按照脂肪酸的不饱和程度和n-3,6-多不饱和脂肪酸归类分析海洋鱼油甘三酯中各类脂肪酸位置分布的特点。结果表明:3种海洋鱼油(凤尾鱼油、金枪鱼油、三文鱼油)中不饱和脂肪酸含量达到60%以上,其中单不饱和脂肪酸(MUFA)占24.67%~33.51%,多不饱和脂肪酸(PUFA)占26.89%~36.15%,而且一半以上PUFA分布在sn-2位,有利于其吸收和提高其耐氧化性;而SFA和MUFA倾向于分布在sn-1,3位上。n-3与n-6PUFAs之间的比例均10,均符合FAO/WHO推荐摄入的标准(4),是理想的n-3PUFA天然营养补充剂。     

生物柴油组分与十六烷值关系研究

采用气相色谱/质谱联用仪对菜籽油甲酯(RME)、地沟油甲酯(WME)、棉籽油甲酯(CME)、棕榈油甲酯(PME)和大豆油甲酯(SME)5种不同生物柴油的组分进行了测定,并通过测定燃料自燃点的方法计算出5种生物柴油的十六烷值.通过对试验数据和相关文献的分析,提出了生物柴油十六烷值预测公式,通过与实测值相比较,证明预测公式可行.     

Mass spectrometric structure analysis of fatty acid mixtures from biological material after gas capillary chromatographical separation

The identification of mixtures of fatty acids from biological materials is possible by electron impact ionization mass spectra of methyl esters after their capillary gas chromatographic separation. Mass spectra of pyrrolidine derivatives are used for the determination of double bond positions in unsaturated fatty acids. 97 different fatty acids (saturated, unsaturated, branched, cyclic, hydroxy, oxo, epoxy and methoxy) and other compounds (alkanes, halogens, phthalates, ketones, aldehydes) were identified in yeast and bacterial biomasses, lipid-containing animal tissues and human sera as well as fish and plant oils (77 preparations).     

Analytical Methods for Quantification of Modified Fatty Acids and Sterols Formed as a Result of Processing

Fats and oils are often submitted to technological treatments before being consumed. Some treatments like refining, hydrogenation, and frying often lead to the formation of modified fatty acids such as cyclic fatty acid monomers (CFAM), geometrical fatty acid isomers, and/or oxidized fatty acids and sterols (cholesterol and phytosterols). Both cholesterol oxidation products (COP) and phytosterol oxidation products (POP), may be present in foods. As some of the newly formed components may present some adverse effects upon consumption, methods have been developed to analyze these compounds in food products and biological samples. Gas liquid chromatography (GC) on long polar columns (100m) is a good choice to quantify trans mono- and poly-unsaturated fatty acids. In some cases a pre-fractionation step using silver nitrate thin layer chromatography (AgNO₃-TLC) may be necessary to avoid GC overlapping of cis and trans isomers. Analysis of CFAM usually involves transformation of the sample in fatty acid methyl esters (FAME) which after addition of an internal standard (IS) are further hydrogenated. An enrichment step using reverse phase high performance liquid chromatography (RP-HPLC) permits to obtain a fraction which consists of a mixture of CFAM and the IS. This fraction is further analyzed by GC on a polar column. The analysis of oxidized triacylglycerol monomers (oxTG) as a group was feasible by a combination of adsorption and size-exclusion chromatography. Quantification in used frying fats and oils around the limit of rejection for human consumption (25% polar compounds) has shown that the amount of oxTG range 5.9–9.4% expressed on fat or oil weight. In foods and biological tissues, the level of oxidized sterols (SOP) is often a very small fraction of their unoxidized forms. Analysis of SOP involved extraction of lipids, saponification or transesterification, enrichment, and subsequent qualitative and quantitative determination by GC and GC-MS, or HPLC and HPLC-MS. In addition, enrichment of SOP requires complete separation from the unoxidized sterols in order to separate these compounds even by high resolution GC capillary columns.