基于FTIR的芝麻油真伪鉴别和掺伪定量分析模型

把低价油掺入到高价油是食用油脂中的常见掺伪现象,芝麻油由于品质好价格高,市场上时有假冒伪劣产品,因此应用FTIR并结合化学计量学,建立了芝麻油的真伪和掺伪的快速分析方法。首先分析了芝麻油与大豆油、葵花籽油在4 000～650 cm-1范围的FTIR谱图,由于食用植物油都是不同脂肪酸甘油三酯的混合物,其谱图极为相似,很难发现芝麻油与其他油脂的明显差异。但是不同食用油的脂肪酸组成不同,其1 800～650 cm-1红外指纹特征区也有所不同,因此可以选择该区域,对红外光谱数据用化学计量学方法进行分类识别。通过建立主成分分析(PCA)和簇类独立软模式识别(SIMCA)模型,进行了芝麻油的真伪鉴别,该模型聚类效果较为理想,识别正确率达到了100％;采用标准正态化校正(SNV)和偏最小二乘法(PLS),经过PCA分析计算,芝麻油中掺入大豆油、葵花籽油的掺伪检测限均为10%;利用FTIR和PLS,建立了芝麻油掺的定量分析模型,该模型预测值与实际值有着良好的对应关系,预测相对误差为-6.87％～8.07％之间,说明定量模型可行。本方法能够实现芝麻油的快速真伪鉴别和掺伪定量分析,其优点是模型一旦建立,分析简便、快速,可以满足大量样品的日常监测。     

Use of Raman spectroscopy for analyzing edible vegetable oils

Vegetable oils provide high nutritional value in the human diet. Specifically, extra virgin olive oil is one of the main ingredients of the Mediterranean diet, which is among the healthiest of eating practices. This article reviews the use of Raman spectroscopy for analyzing edible vegetable oils including olive oil. Although the spectra for edible vegetable oils are similar, they exhibit some differences which, however small, enable their discrimination. Thus, Raman spectra allow one to determine the degree of unsaturation of oils. This property is correlated with the iodine value but much faster and simpler to obtain. The degree of unsaturation can be used to classify and authenticate oils, which is especially useful with high-quality oils. In fact, adulteration with mixtures of more inexpensive oils can be easily detected by Raman spectroscopy. This technique additionally allows some minor components present in unsaponifiable matter to be identified. Fats in general and vegetable oils in particular, are prone to oxidation. Thus, double bonds in them are oxidized to form triglycerides. Vegetable oils are widely used for frying and Raman spectroscopy allows for their oxidative stability against heating at the usual frying temperatures to be assessed.     

基于衰减全反射式太赫兹时域光谱技术的食用油光谱特性研究

食用油是人类营养和能量的重要来源,为人体提供必需的脂肪酸,研究食用油在太赫兹波段光学特性,对食用油成分分析及品质评价具有重要价值。衰减全反射式太赫兹时域光谱技术是一种新型的太赫兹时域光谱技术,通过样品与倏逝波的相互作用,获取样品的太赫兹光谱。与透射式或反射式太赫兹时域光谱技术相比,该技术能有效地避免测量食用油等液体样品时样品池对光学参数的影响,并能获得样品的精确光学参数。分别利用透射式太赫兹时域光谱技术和衰减全反射式太赫兹时域光谱技术测量了大豆油的吸收光谱。结果表明,与透射式太赫兹时域光谱技术相比,衰减全反射式太赫兹时域光谱技术能更有效地提取大豆油的吸收系数、吸收峰分布等光学特性。进一步利用衰减全反射式太赫兹时域光谱技术研究了大豆油、核桃油、葡萄籽油在太赫兹波段的光学特性,获得了三种食用油在1~1.8 THz范围内的折射率谱和吸收光谱。利用密度泛函理论计算了食用油中四种主要成分(软脂酸、硬脂酸、油酸和亚油酸)在太赫兹波段的振动、转动模式,理论计算结果同实验测量结果吻合较好。研究表明,在太赫兹波段食用油的吸收峰与所含脂肪酸分子种类与含量有关,其主要来源为脂肪酸分子的低频振动和转动。研究成果对食用油成分定性定量分析及品质检测等具有指导意义。     

可见/近红外联合UVE-PLS-LDA鉴别压榨和浸出山茶油

山茶油是我国特有的优质食用油,而压榨山茶油营养品质优于浸出山茶油。采用可见/近红外光谱技术对压榨和浸出山茶油进行鉴别研究。在350～1 800 nm波段范围内采集压榨和浸出山茶油样本的透射光谱,利用无信息变量消除(UVE)方法进行波长变量优选,剔除无用波长变量,并应用偏最小二乘-线性判别分析(PLS-LDA)建立鉴别分类模型。最后,利用鉴别分类模型对未参与建模的26个预测集样本进行鉴别。研究结果表明,UVE-PLS-LDA是一种有效的鉴别分类方法,所建立的鉴别分类模型能较好地对压榨和浸出山茶油进行鉴别,校正集和预测集样本的鉴别正确率均为100%。因此,可见/近红外光谱联合UVE-PLS-LDA方法鉴别压榨和浸出山茶油是可行的。     

Analysis of Argan Oil Adulteration Using Infrared Spectroscopy

The determination of argan oil adulteration by other vegetable oils is a real analytical challenge. The authentication of argan oil needs fast and simple analytical techniques for quality control and testing. This study focuses on the detection and quantification of argan oil adulteration with different edible oils, using midinfrared spectroscopy with chemometrics. Chemometric treatment of MIR spectra has been assessed for the classification and quantification of argan oil adulteration with sunflower or soybean oils. The potential of MID spectroscopy combined with partial least squares regression (PLS) as a rapid analytical technique for the quantitative determination of adulterants in argan oil has been demonstrated. A PLS model has been established to predict the concentration of soybean and sunflower oil as adulterants in the calibration range between 0% and 30% (w/w) in argan oil with good prediction performances in the external validation.     

精油中挥发性成分GC/FTIR与GC/MS联合分析

采用同时蒸馏萃取(SDE)法获得了香紫苏(Salvia sclarea L.)精油,利用气相色谱/傅里叶变换红外光谱联用(GC/FTIR)和气相色谱/质谱联用(GC/MS)相结合的手段,对其挥发成分进行了定性和定量分析,着重讨论了GC/FTIR在精油分析中的应用研究。通过不同波数官能团(Gram-Schmidt)重建红外光谱图、红外光谱差谱技术及质谱等相互验证的方法,大大提高了香紫苏油挥发成分的定性分析准确性。     

Ultrasonic analysis of edible fats and oils

Low intensity ultrasound is a powerful analytical technique for investigating the physico-chemical properties of many biological and non-biological materials. In this article its application for the characterization of edible fats and oils is assessed. Ultrasound can be used to determine the dynamic rheology and composition of oils, the oil content and droplet size of emulsions and the solid fat content of partially crystalline emulsions. It is capable of rapid and precise measurements, is non-destructive and non-invasive, can be used on-line or off-line and is relatively inexpensive. Ultrasonic techniques will therefore prove a useful addition to the existing analytical techniques used to characterize fats and oils.     

板蓝根颗粒的红外光谱无损快速鉴别及可视化表达

用傅里叶变换红外光谱对传统中成药板蓝根颗粒进行了研究。对同一厂家不同批次和不同厂家的板蓝根颗粒主要成分板蓝根和大青叶的红外光谱图及二阶导数谱图进行了比较分析,并将谱图进行可视化表达。结果显示,傅里叶变换红外光谱法结合二阶导数谱和谱图的可视化,能够有效地提取配方颗粒的特征指纹谱图,直观地反映出不同生产厂家产品质量的差别及同一生产厂家不同批号产品之间谱图的可重现性,从而实现中成药的无损快速鉴别,为中成药质量检测及监控提供一种方便、有效和直观的方法。     

基于太赫兹时域光谱的食用油过氧化值定量分析研究

针对目前太赫兹光谱技术在食用油品质检测方面存在定性多、定量难的问题,提出一种基于衰减全反射（ATR）式太赫兹时域光谱（THz-TDS）技术的食用油过氧化值定量分析方法。首先采集不同种类、不同氧化程度食用油样本的太赫兹时域光谱图,筛选有效信号波段并提取得到光学常数,经预处理算法校正后的光学常数,结合多种化学计量学方法建立定量分析模型,实现快速、无损预测食用油的过氧化值。70个实验样本包括大豆油、菜籽油和玉米,过氧化值覆盖范围0.41~10.23 mmol·kg-1,且样本的过氧化值均匀分布。采用TeraView公司生产配有ATR检测模块的TeraPulse 4000太赫兹脉冲光谱系统采集样本THz-TDS信号,根据THz-TDS谱图信号特征筛选有效波段10~86.78 cm-1用于建模分析。通过快速傅里叶变换得到频域信号并从中提取光学常数：折射率和吸收系数,采用Savitzky-Golay7点卷积平滑分别对折射率和吸收系数进行预处理,去除干扰信号。运用SPXY算法按照3∶1比例划分校正集和预测集样本,结合主成分回归法、偏最小二乘法两种化学计量学分析方法,分别建立基于折射率和基于吸收系数的过氧化值分析模型。对模型评价指标均方根误差和相关系数进行分析,基于折射率的过氧化值分析模型采用偏最小二乘算法建模预测精度最理想,选取最优主成分数为6时,其校正集均方根误差RMSEC为0.168%、决定系数R2为0.981,预测集均方根误差RMSEP为0.231%、决定系数r2为0.977;基于吸收系数的过氧化值分析模型则采用主成分回归算法建模预测模型稳健度最好,选取最优主成分数为10时,其校正均方根误差RMSEC为0.192%、校正集决定系数R2为0.979,预测均方根误差RMSEP为0.262%、预测集决定系数r2为0.97。该研究结果的得出,验证了THz-TDS技术用于食用油过氧化值定量分析的可行性,为食用油的品质评价找到一种高精度、性能稳定、快速无损的检测方法。     

基于液芯光纤的激光诱导荧光食用油种类鉴别研究

组建了一套基于液芯光纤的激光诱导荧光食用油鉴别装置。研究了不同液芯光纤长度对食用油激光诱导荧光光谱的影响,分析了不同种类食用油激光诱导荧光光谱之间的差异。八种食用油共320份样本荧光数据在1 m长液芯光纤内采集,采用主成分分析方法对食用油荧光数据进行降维处理,利用偏最小二乘判别分析(PLS-DA)方法建立食用油种类的鉴别模型。结果表明,使用液芯光纤后,食用油荧光强度得到较大的增强。随着液芯光纤长度增加,食用油荧光特征峰逐渐增加并且食用油的激光诱导荧光光谱会产生红移现象,当液芯光纤长度超过80 cm后,红移趋于饱和。不同食用油的荧光光谱形状差异较大,可用于区分不同种类食用油。利用主成分1和主成分2绘制的主成分得分图显示,不同种类食用油呈现很好的聚集。当选用主成分数为10时,建立的PLS-DA食用油种类鉴别模型对训练集和预测集样本识别率均达到100%。说明本装置用于食用油种类的快速鉴别具有较高的准确性。     

基于拉曼光谱的食用植物油快速鉴别

提出了一种基于拉曼光谱的食用植物油快速鉴别方法。基于已知类别的食用植物油样本进行建模,首先对原始拉曼谱图进行基线校正和标准归一化等预处理,并选取食用油不饱和度特征的两处拉曼峰值作为特征向量,计算训练样本特征空间上各个植物油类别的中心坐标;然后,将食用植物油测试样本的拉曼谱图经过相同预处理和特征提取,获取测试样本的特征向量,计算其与各类别中心坐标的欧式距离,根据类中心最小距离法,取欧式距离最小的那一类作为预测样本的类别。针对7类43个食用植物油样本的实验结果表明,采用食用油不饱和度两点描述法进行特征提取,各类别样本聚集效果比PCA好,类间距更大。上述鉴别方法可以准确地实现食用植物油品种的快速分类。     

二组分食用混合油的线性混合模型研究与应用

基于二组分混和食用油的吸收系数是各自组分吸收系数按照掺杂比例的线性组合的假设以及朗伯-比尔吸收机理,提出并推导了二组分食用混合油的线性混合数学模型。该数学模型可根据相同厚度的两种原料油和其二组分混合油对相同光源的吸收光强变化计算出混合油的组分比例。根据误差理论,利用全微分公式分析了组分比例计算值的误差,表明通过选择使两种原料油的透射光强和吸光度差值的乘积较大的波长位置,可以优选出检测波长。搭建了可见-近红外光谱检测系统,利用花生油掺杂玉米油、花生油掺杂大豆油和玉米油掺杂大豆油三种混合油对模型进行了验证。结果表明,该模型对掺杂10%以上的混合油的成分比例计算值和实际值的相对误差在5%以内,相关系数分别达到0.999 4,0.999 7和0.999 3,标准误差分别为0.006 9,0.005 1和0.007 6,并证实本研究的波长选取方法是合理的。此外,对3种按同样比例组合的、未混合的分立油样本进行了检测,计算组合比的相对误差也可控制在10%以内,同时揭示入射光源的平行度和待测装置的垂直度对检测精度有一定影响。试验证明,不同于传统的光谱结合化学计量学的检测方法,本方法可以仅通过检测原料油和混合油在选定波长上的吸收光强即可准确计算得到掺杂比例。     

Development of the Miniature NMR Apparatus for Edible Oil Quality Control

Edible oils are necessary in daily cooking; therefore, it is significantly important to find an efficient scheme for its quality control. In this work, a miniature nuclear magnetic resonance (NMR) apparatus was set up for the identification of edible oils with different qualities. Experimental results show that the total transverse relaxation time of the commercial refined edible oil is shorter than the poor quality edible oil. Further data processing was performed with inverse Laplace transformation for transverse relaxation time distribution analysis. The spectra of the distribution of transverse relaxation times of different qualities edible oils are also significantly different, among which, the refined edible oil has two peaks whereas the poor quality edible oil has three peaks. The experimental results are well agreed with the theoretical analysis. As the miniature NMR apparatus was employed to analyze three suspected illegal cooking oils which were seized at the scene of inspection, the three oils were all confirmed to be poor quality edible oils. The apparatus can also detect refined edible oils adulterated with illegal cooking oils. In conclusion, the presented miniature NMR apparatus could be a potential tool for edible oil quality control.     

海刺参及其产品红外光谱的分析与鉴定

作为高档的保健品,深加工的海刺参产品如海刺参注射液、海刺参胶囊等,有着广阔的市场前景,但是目前还没有统一有效的品质鉴定手段和标准。作者采用傅里叶变换红外光谱法(FTIR)和二维相关红外光谱技术(2DIR)对海刺参粉末进行分析,得到了自制海刺参粉的谱图,然后以此为标准对五个不同厂家的海刺参胶囊进行相关性比较,结果显示大连海晏堂的海刺参胶囊与作者自制的鲜活冻干样品最为相符,这表明它基本上是纯的冷冻干燥海刺参粉;实验还表明通过建立标准红外谱图库来监控海刺参产品质量、制定统一标准是完全可能的。     

基于紫外拉曼光谱的转基因大豆油快速识别方法研究

转基因技术对实现作物增产增质,降低农药使用量,降低生产成本等具有重要作用,但对生态环境也存在一定的潜在威胁。为了防止转基因大豆在食品化中的滥用,对转基因产品快速鉴别技术的研究尤为迫切。紫外拉曼光谱检测技术具备外场远距离无损遥测检测,简单高效,快速准确等优点,可有效用于物质遥测鉴别领域。基于紫外拉曼光谱的转基因/非转基因大豆油以及与其他类别食用油鉴别方法,采集了五种不同食用油(两种品牌转基因/非转基因大豆油各500组样本和一种稻米油100组样本,共2 100组样本)在3 500~400 cm-1(268~293 nm)范围内的日盲紫外拉曼光谱信息,为提高光谱数据的信噪比并保证分类识别的准确性,对上述光谱数据采用Savitzky-Golay滤波降噪、基于自适应迭代加权惩罚最小二乘法(airPLS)的基线校正以及多元散射校正(MSC)的光谱数据修正等预处理。根据大豆油的紫外拉曼指纹图谱,分析出主要化学成分包含脂肪类、蛋白质类、酰胺类。将每种大豆油样本按1∶1划分为训练集和测试集,输入训练集数据至支持向量机(SVM)进行训练,采用10折交叉验证建立最佳模型,识别准确率达99.81%,对转基因大豆油的判别效果显著;采用主成分分析法(PCA)进行数据降维处理,提取出8个主成分,累计贡献率为74.84%,可代表大部分原始数据特征。在此基础上,将预处理后的光谱数据按4∶1划分为训练集和测试集,采用偏最小二乘回归判别分析方法(PLS-DA),结合10折交叉验证法建立全谱的最佳PLS-DA模型(判别阈值设置为0.5),判别准确率达到70.95%。研究表明,紫外拉曼光谱分析方法可较为准确地鉴别非转基因/转基因大豆油,同时可鉴别大豆油与稻米油,实现对转基因大豆食品的快速无损鉴别,可望成为转基因大豆油及其食品的现场检测新的技术途径,对推动转基因产品遥测鉴别技术的发展具有进步意义。     

衰减全反射红外光谱法快速分类和识别多种食用油的方法

提出了一种衰减全反射红外光谱法快速分类和识别多种食用油的方法——KL-BP模型。此模型利用KL算法对原始光谱数据分类特征进行提取并对原始数据降维,降维后的数据作为神经网络的输入建立分析模型。实验共收集了九种食用油包括芝麻油、玉米油、油菜籽油、调和油、葵花油、花生油、橄榄油、大豆油、茶籽油,共84个样品,并测定了其衰减全反射红外光谱。为了对比所提方法性能,分别建立PCA直接分类、KL直接分类、PLS-DA、PCA-BP和KL-BP模型的分类结果进行对比。研究结果表明,对所研究的9种食用油,PCA直接分类、KL直接分类、PLS-DA、PCA-BP和KL-BP方法的识别率分别为59.1%,68.2%,77.3%,77.3%和90.9%。在数据降维中,KL算法通过分别提取使类间距离和类内距离比值最大方向的特征向量提取和包含在类内离散度矩阵中的分类信息,能够比PCA方法提取了更多的分类信息;引入BP神经网络能有效地提高分类能力和分类准确率;KL-BP综合了KL对分类信息提取优势以及BP神经网络自学习、自适应、非线性的优点,在分类和识别成分相近的9种食用油中表现出了最优秀的能力。     

Possibility of Light-Induced Mid-IR Emission in <Emphasis Type="Italic">Situ</Emphasis> Analysis of Plants

We perform the spectral analysis of fresh leaves using light-induced mid-IR emission spectroscopy (LIMIRES), a technique utilizing CW optical pumping for preparing and monitoring vibrationally excited states of chromophores. We show how to obtain high-quality IR-emission spectra of intact leaves using visible light of low intensity and sensitive Fourier transform infrared spectroscopy (FTIR). Changing the conditions of illumination, we carry out the spectral discrimination between leaf samples of wild plants and transgenic tobacco plants. Our results show that LIMIRES is a valuable new technique for studying the vibrational structure of excited pigments as well as the nondestructive monitoring of the quality of tobacco leaves.     

部分动植物油的拉曼光谱研究

利用拉曼光谱技术分别研究了植物油和动物脂肪油的光谱特性。通过自适应迭代惩罚最小二乘法的基线校正方法, 对所测得的拉曼光谱进行了数据处理,获得了它们的微观信息。进而通过选取其中部分油的拉曼光谱,进行了植物油的光谱、动物脂肪油的光谱以及动物脂肪油和植物油之间的光谱比较和分析,从而发现了多种植物油光谱(包括多个频移范围内的频移大小以及强度大小)的差异,也发现了动物脂肪油与植物油的拉曼光谱间的差异。不但提供了辨识不同食用油的光谱依据,也证明了拉曼光谱是一种识别不同油品的有效方法。     

Deterioration of edible oils during food processing by ultrasound

During food emulsification and processing of sunflower oil (most used edible oil), a metallic and rancid odour has been detected only for insonated oil and foods. Some off-flavour compounds (hexanal and hept-2-enal) resulting from the sono-degradation of sunflower oil have been identified. A wide variety of analytical techniques (GC determination of fatty acids, UV spectroscopy, free fatty acids and GC/MS) were used to follow the quality of insonated sunflower oil and emulsion. Different edible oils (olive, sunflower, soybean, em leader ) show significant changes in their composition (chemical and flavour) due to ultrasound treatment.     

Application of step-scan FTIR to the research of quantum cascade lasers

The principle of step-scan Fourier transform infrared (FTIR) spectroscopy is introduced. Double modulation step-scan FTIR technique is used to obtain the quantum cascade laser's stacked emission spectra in the time domain. Optical property and thermal accumulation of devices due to large drive current are analyzed.