LF-NMR结合化学模式识别鉴别油脂种类及餐饮废弃油脂

应用主成分分析(Principal component analysis,PCA)和聚类分析法(Cluster analysis,CA)对9种(27个)常见食用植物油及100个餐饮废油的低场核磁共振(Low-field nuclear magnetic resonance,LF-NMR)(T2)弛豫特性数据进行分析。结果表明:在正常食用油种类区分方面,主成分分析的效果较优,9种食用油在主成分分布图上按种类正确分组,边界清晰。而在正常食用油与餐饮废油的区分方面,聚类分析效果较优,引入30个待测样本后,聚类分析(127个样品,欧式距离=5)的正确率为94.49%,分析误判率为5.51%,分组效果良好。LF-NMR结合化学模式识别可实现对油脂种类及餐饮废弃油脂的鉴别。     

食用油识别方法的研究

建立了用气相色谱－氢火焰离子检测器（ＧＣ－ＦＩＤ）准确测定了各种食用油中所有脂肪酸含量的方法，提出用脂肪酸含量的分布和相对不饱和度（Ｕ／Ｓ）来识别食用油，识别模型简便可靠，从而达到识别掺假的目的。     

非正常食用油的在线甲基化-气相色谱测定及模式识别分析研究

建立了食用油中脂肪酸组成的在线水解甲基化-气相色谱测定方法,分析了20余种常用食用油与非正常食用油样品。将1μL(3 mg/mL)油脂样品与2μL衍生化试剂四甲基氢氧化铵(TMAH,25%甲醇溶液)加入裂解器,在350℃下,油脂加水分解瞬间衍生化成相应的脂肪酸甲酯。基于气相色谱图上分离鉴定到的10个共有峰的相对强度,建立了食用油的气相色谱指纹图谱。结合化学模式识别即主成分分析和系统聚类分析对合格食用油和非正常食用油样品的色谱图进行了识别分析。结果表明,建立的指纹图谱结合模式识别技术可以较好的区分合格食用油与非正常食用油样品。     

牡蛎中脂肪酸在储藏过程中的稳定性

用超临界流体萃取 (SFE)及GC MS分析了新冷冻干燥及保存 1 5d ,30d ,45d ,60d ,75d ,90d后的鲜牡蛎粉中的 2 3种脂肪酸组分的质量分数。发现在存放过程中牡蛎脂肪酸的稳定性与其不饱和度有关 ;不饱和度越高 ,脂肪酸越易被氧化 ,其中多不饱和脂肪酸的氧化是逐渐进行的 ,没有特定的稳定期。放置 90d后 ,牡蛎脂肪酸中脑黄金EPA的质量分数由原来的 1 6 94%降至 5 43% ,DHA由 9 2 5%降至 2 86%。     

油脂中脂肪酸的气相毛细管色谱法分析

人类利用油脂已有悠久的历史。油脂是人类不可缺少的营养物质,而且对人体具有重要的生理功能。 油脂的主要成分是脂肪酸甘油脂。自然界中油脂的种类很多,不同的油脂具有不同的脂肪酸组成,因而具有不同的功能和价值。亚油酸是人体必需的     

生物柴油树种油脂脂肪酸组成对燃料特性的影响

以目前中国主要开发或具有开发潜能的10种生物柴油树种为研究对象,分析其果实或种子油脂脂肪酸组成对合成生物柴油燃料特性的影响。结果表明,木本植物生物柴油产品十六烷值、碘值、氧化安定性等燃料特性主要由原料油脂肪酸的不饱和度决定,脂肪酸不饱和度低于133.13,十六烷值(GB/T 20828-2007)和碘值(EN 14214)就可以达标。生物柴油产品冷滤点随着长碳链饱和脂肪酸的增加而升高,脂肪酸饱和碳链长度因子分别小于8.41和2.72时,可以满足冷滤点0℃和-10℃的要求。高品质生物柴油的原料中应该具有较高的单元不饱和脂肪酸含量。通过油脂脂肪酸单不饱和脂肪酸、多不饱和脂肪酸和饱和脂肪酸的组成绘制出生物柴油特性三角预测图,为预测生物柴油产品燃料特性提供参考依据。     

~(13)C-NMR对油脂的定量测定

本工作用外加驰豫试剂及反转门控去偶方式对菜籽油和“营养”油进行了~(13)C-NMR谱的定量测定。在归属各峰基础上,认为该两油脂都以甘油酯形式存在。提出了①多烯类结合脂肪酸占烯类总量的摩尔分数P;②烯碳数与饱和碳数之比R;③包括同种油脂及不同油脂间的油脂分子各类功能团的相对含量的测定计算表达式。     

海棠果种子油脂肪酸成分研究

用乙醚萃取海棠果种子油,油脂皂化后的脂肪酸采用三氟化硼-甲醇溶液进行甲酯化.采用气相色谱-质谱-计算机联用技术分离、鉴定出7种主要脂肪酸,进一步采用气相色谱法定量测定脂肪酸,分别为肉豆蔻酸0.02%,软脂酸8.64%,硬脂酸8.96%,油酸37.7%,亚油酸20.1%,亚麻酸0.38%,二十碳酸0.85%.结果表明,海棠果种子油不饱和脂肪酸质量分数高达58%,值得作为不饱和脂肪酸食用油来源开发.     

腐殖酸磁固相萃取与高效液相色谱-荧光检测联用测定食用油中的苯并芘

采用简单的混合研磨方法制备磁性腐殖酸(MHAS)复合材料,并将其作为磁固相萃取的吸附剂选择性分离和富集食用油脂中的苯并芘(BaP)。结合高效液相色谱-荧光检测法(HPLC-FLD),建立了食用油中BaP检测的新方法。该方法整个样品前处理过程在15min内即可完成,对目标物BaP的检测限低至0.04ng/g,在0.1~100ng/g范围内线性良好(R=0.999),日内(n=5)和日间(n=3)相对标准偏差分别小于3.5%和15.8%。将该方法应用于多种食用油中BaP的检测,每种食用油中均有不同含量的BaP被检出,对12种常见食用油的加标回收率在74.2%至120.6%之间,相对标准偏差小于11.0%。     

气相色谱-质谱技术结合化学计量学对6种植物油进行判别分析

测定了6种不同种类植物油(茶籽油、大豆油、花生油、葵花籽油、玉米油和芝麻油)的脂肪酸组成及含量,旨在探讨利用植物油脂肪酸的指标对不同种类的植物油进行分类和判别的可能性。采用气相色谱-质谱联用技术,对6种不同植物油中脂肪酸的组成和含量进行测定,用SPSS.19.0统计软件进行主成分分析、聚类分析和判别分析。对6种不同植物油脂肪酸进行分析、对比,得出植物油脂的主要成分为C16∶0,C18∶0,C18∶1 cis-9,C18∶2 cis-9,12和C18∶3 cis-9,12,15。这5种主要脂肪酸的总含量在茶籽油、大豆油、花生油、葵花籽油、玉米油和芝麻油中分别为98.455%,97.586%,89.019%,97.378%,98.294%和98.021%。6种植物油的不饱和度(U/S)均大于2.000,其中最小为花生油2.055,最大为茶籽油3.976。进行主成分分析降维得到前3个主成分,因为前3个主成分的特征//值均大于1且累计贡献率达到80.060%,第1主成分的贡献率为35.853%,第2主成分的贡献率为23.847%,第3主成分的贡献率为20.360%。建立了3个典则判别函数,典则判别函数的相关系数均大于0.990,且对于茶籽油、大豆油、花生油、葵花籽油、玉米油和芝麻油的初始分类正确率为100.0%,交叉验证正确率为100.0%。     

Trace elemental characterization of edible oils by ICP-AES and GFAAS

A method for the determination of the inorganic profile in edible oils is proposed. The quantification of selected metals in various oils (olive, pumpkin seed, sunflower, sesame seed, hazelnut, grape, soya, rice oil) was carried out using microwave assisted digestion followed by ICP-AES and GFAAS. The detection power of the ICP-AES technique was sufficient for the determination of Ca, Fe, Mg, Na, and Zn. Since the samples contained very low amounts of Al, Cu, Co, Cr, K, Ni, Mn, and Pb, these elements were measured by GFAAS. Differences of metal concentrations for edible oils obtained in this preliminary study represent a starting basis for the development of an additional analytical procedure applicable for oil characterization.     

Rapid screening of mixed edible oils and gutter oils by matrix-assisted laser desorption/ionization mass spectrometry

Authentication of edible oils is a long-term issue in food safety, and becomes particularly important with the emergence and wide spread of gutter oils in recent years. Due to the very high analytical demand and diversity of gutter oils, a high throughput analytical method and a versatile strategy for authentication of mixed edible oils and gutter oils are highly desirable. In this study, an improved matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) method has been developed for direct analysis of edible oils. This method involved on-target sample loading, automatic data acquisition and simple data processing. MALDI-MS spectra with high quality and high reproducibility have been obtained using this method, and a preliminary spectral database of edible oils has been set up. The authenticity of an edible oil sample can be determined by comparing its MALDI-MS spectrum and principal component analysis (PCA) results with those of its labeled oil in the database. This method is simple and the whole process only takes several minutes for analysis of one oil sample. We demonstrated that the method was sensitive to change in oil compositions and can be used for measuring compositions of mixed oils. The capability of the method for determining mislabeling enables it for rapid screening of gutter oils since fraudulent mislabeling is a common feature of gutter oils.     

A computer program for the automatic identification of edible oils by gas—liquid chromatography

A computer program is given for the identification of edible oils from their fatty acid ratios. The program was used with the Hewlett-Packard 3354 Laboratory Automation System in autocall mode to identify a number of vegetable oils from the fatty acid ratios determined by gas chromatography of the trans-esterified oil samples.     

Development of a voltammetric electronic tongue for discrimination of edible oils

In this paper, we propose a novel strategy to perform cyclic voltammetric measurements with a platinum microelectrode directly in edible oil samples. The microelectrode was employed as an electronic tongue that, along with the application of chemometrics to the current–potential responses, proved useful for discriminating oils on the basis of their quality and geographical origin. The method proposed here is based on the use of suitable room temperature ionic liquids, added to oils as supporting electrolytes to provide conductivity to the low-polarity samples. The entire voltammograms, recorded directly on the oil/RTIL mixtures, were processed via principal component analysis and a classification technique (K nearest neighbors), to extract information on samples characteristics. Data processing showed that oils having different nature (i.e. maize and olive) or geographical origin (i.e. olive oils coming from different regions) can be distinguished.     

Polycyclic aromatic hydrocarbons (PAHs) in edible oils by gas chromatography coupled with mass spectroscopy

The occurrence of polycyclic aromatic hydrocarbons (PAHs) in nine edible oils of three categories of oil samples, such as soy bean oil, mustard oil and coconut oil, has been studied to determine the contamination degree of this type of oil samples. Eight major carcinogenic polycyclic aromatic hydrocarbons (PAHs), such as naphthalene, anthracene, phenanthrene, fluorene, pyrene, crysene, benzo(a)pyrene and benzo(a)anthracene, were identified and quantified in the extract of edible oils collected from Bangladeshi Markets by gas chromatography and mass spectroscopy. All of the carcinogenic PAHs are not present in the edible oils. A few of the carcinogenic PAHs are present in the oils but it is within the permissible limit. The results for the recoveries of naphthalene, fluorene, phenanthrene, anthracene, pyrene, crysene, benzo(a)anthracene and benzo(a)pyrene were in the range of 56–84%. The limit of detection (LOD) of the GC–MS method, established at signals three times that of the noise for naphthalene, fluorene, phenanthrene, anthracene, pyrene, crysene, benzo(a)anthracene and benzo(a)pyrene, was 2.0–2.5 ng, respectively.     

Effort to improve the quantitative determination of oxidation and hydrolysis compound classes in edible vegetable oils.

This paper proposes an analytical method to evaluate the classes of products of polymerization, oxidation and hydrolysis as well as the polar compounds present in refined edible oils in a more reliable fashion. The polar compounds of a marketed refined peanut oil were analyzed by preparative gel permeation chromatography and the classes of substances corresponding to single chromatogram peaks were collected by means of a fraction collector, purified and used as standards for high-performance size-exclusion chromatographic analysis. The linearity of detector response, the precision and accuracy of the method for each class of compounds and for polar compounds were assessed. Another aim was to verify whether this method may be applied to other refined peanut oils and to edible vegetable oils in general, even of different botanical origin, using the standards that had already been prepared for that particular peanut oil. The results obtained showed that this was possible and the analytical method developed can be extended to the most common edible vegetable oils.     

Infrared study of aging of edible oils by oxidative spectroscopic index and MCR-ALS chemometric method

One of the most suitable analytical techniques used for edible oil quality control is Fourier transform mid infrared spectroscopy (FT-MIR). FT-MIR spectroscopy was used to continuously characterize the aging of various edible oils thanks to a specific aging cell. There were differences in the spectra of fresh and aged oils from different vegetable sources, which provide the basis of a method to classify them according to the oxidative spectroscopic index value. The use of chemometric treatment such as multivariate curve resolution-alternative least square (MCR-ALS) made it possible to extract the spectra of main formed and degraded species. The concentration profiles gave interesting information about the ability of the various oils to support the oxidative treatment and showed that all oils present the same aging process. Both methods led to concordant results in terms of induction times determined by the oxidative spectroscopic index and the appearance of oxidation products revealed by MCR-ALS.     

Total luminescence spectroscopy with pattern recognition for classification of edible oils

Total luminescence spectroscopy combined with pattern recognition has been used to discriminate between four different types of edible oils, extra virgin olive (EVO), non-virgin olive (NVO), sunflower (SF) and rapeseed (RS) oils. Simplified fuzzy adaptive resonance theory mapping (SFAM), traditional back propagation (BP) and radial basis function (RBF) neural networks provided 100% classification for 120 samples, SFAM was found to be the most efficient. The investigation was extended to the adulteration of percentage v/v SF or RS in EVO at levels from 5% to 90% creating a total of 480 samples. SFAM was found to be more accurate than RBF and BP for classification of adulterant level. All misclassifications for SFAM occurred at the 5% v/v level resulting in a total of 99.375% correctly classified oil samples. The percentage of adulteration may be described by either RBF network (2.435% RMSE) or a simple Euclidean distance relationship of the principal component analysis (PCA) scores (2.977% RMSE) for v/v RS in EVO adulteration.     

气相色谱-负化学源质谱联用法测定水产品及食用油中氟乐灵的残留量

建立了一种可用于水产品及食用油中氟乐灵残留量分析的分散型固相萃取-气相色谱-负化学离子源质谱方法。水产品及食用油经乙腈提取,4 ℃冷藏后,采用分散型固相萃取法净化,由气相色谱-负化学离子源质谱选择离子监测技术进行测定与确证,同位素内标法定量。在1~40 μg/L范围内氟乐灵农药的线性关系良好;方法定量限（LOQ）为0.02 μg/kg;对鳗鱼、烤鳗、梭子蟹、小龙虾、猪油和橄榄油等6种复杂基质进行1.0、2.0和3.0 μg/kg等3个水平的添加回收试验,平均回收率均处于80%~100%之间,RSD≤10.3%;无干扰现象出现。该方法可作为水产品及食用油中氟乐灵残留检测的确证方法。     

Chemometric assessment of thermal oxidation of some edible oils

The effect of microwave heating was studied in six varieties of edible oil. Variations in physicochemical properties were observed and compared with the data obtained by hot plate heating. Fourier-transform infrared spectra of the oils showed substantial variations after both types of heating in the region of hydrogen’s stretching (C–H) vibration, region of double bond’s stretching (C=O), and fingerprint region. The visible spectra of mustard and olive oil showed the reduction in carotenoid, flavonoid, and chlorophyll pigments after heating. The oil samples were discriminated as saturated, monounsaturated, and polyunsaturated fats using chemometric techniques on physical and spectroscopic measurements.