Detection of inverted beet sugar adulteration of honey by FTIR spectroscopy

A combination of Fourier transform infrared (FTIR) spectroscopy and multivariate statistics as a screening tool for the determination of beet medium invert sugar adulteration in three different varieties of honey is discussed. Honey samples with different concentrations of beet invert sugar were scanned using the attenuated total reflectance (ATR) accessory of the Bio‐Rad FTS‐6000 Fourier transform spectrometer. The spectral wavenumber region between 950 and 1500 cm^?1 was selected for partial least squares (PLS) regression to develop calibration models for beet invert sugar determination in honey samples. Results from the PLS (first derivative) models were slightly better than those obtained with other calibration models. Predictive models were also developed to classify beet sugar invert in three different varieties of honey samples using discriminant analysis. Spectral data were compressed using the principal component method, and linear discriminant and canonical variate analyses were used to detect the level of beet invert sugar in honey samples. The best predictive model for adulterated honey samples was achieved with canonical variate analysis, which successfully classified 88–94 per cent of the validation set. The present study demonstrated that Fourier transform infrared spectroscopy could be used for rapid detection of beet invert sugar adulteration in different varieties of honey. © 2001 Society of Chemical Industry     

Rapid determination of Swiss cheese composition by Fourier transform infrared/attenuated total reflectance spectroscopy

There is a need for rapid and simple techniques that can be used to predict the quality of cheese. The aim of this research was to develop a simple and rapid screening tool for monitoring Swiss cheese composition by using Fourier transform infrared spectroscopy. Twenty Swiss cheese samples from different manufacturers and degree of maturity were evaluated. Direct measurements of Swiss cheese slices (∼0.5g) were made using a MIRacle 3-reflection diamond attenuated total reflectance (ATR) accessory. Reference methods for moisture (vacuum oven), protein content (Kjeldahl), and fat (Babcock) were used. Calibration models were developed based on a cross-validated (leave-one-out approach) partial least squares regression. The information-rich infrared spectral range for Swiss cheese samples was from 3,000 to 2,800 cm⁻¹ and 1,800 to 900 cm⁻¹. The performance statistics for cross-validated models gave estimates for standard error of cross-validation of 0.45, 0.25, and 0.21% for moisture, protein, and fat respectively, and correlation coefficients r > 0.96. Furthermore, the ATR infrared protocol allowed for the classification of cheeses according to manufacturer and aging based on unique spectral information, especially of carbonyl groups, probably due to their distinctive lipid composition. Attenuated total reflectance infrared spectroscopy allowed for the rapid (∼3-min analysis time) and accurate analysis of the composition of Swiss cheese. This technique could contribute to the development of simple and rapid protocols for monitoring complex biochemical changes, and predicting the final quality of the cheese.     

Differentiation of saffron from four countries by mid-infrared spectroscopy and multivariate analysis

Mid-infrared spectroscopy combined with multivariate analysis has been applied for the discrimination of 250 saffron samples from Greece (40 samples), Iran (87 samples), Italy (60 samples) and Spain (63 samples). The infrared spectra of saffron filament samples and their organic extracts were recorded. Principal component analysis was applied to different spectral regions. Then the principal components were used as variables in discriminant analysis. The best discriminatory approach was achieved in the spectral region 2000–700 cm⁻¹. The spectral region responsible for the differentiation of Italian samples is in the region of carbonyl group around 1746 cm⁻¹. The spectral region at around 1600 cm⁻¹ and the band at 1670 cm⁻¹ are responsible for the differentiation of samples from the remaining countries. From the original grouped cases, 93.6% were correctly classified. The correct classification rates for saffron samples from Greece, Iran, Italy and Spain were 90.0, 89.5, 96.7 and 98.4%, respectively. The combination of infrared spectroscopic technique with multivariate analysis is a rapid and ambient method to discriminate saffron samples in terms of geographical origin.     

A Fourier Transform Infrared Spectroscopy Method for Analysis of Palm Oil Adulterated with Lard in Pre-Fried French fries

Fourier transform infrared spectroscopy with attenuated total reflectance accessory was used to detect the presence of lard in French fries pre-fried in palm oil adulterated with lard. A Fourier transform infrared calibration model was obtained using partial least squares for prediction of lard in a blend mixture of lard and palm oil. The coefficient of determination (R²) of 0.9791 was obtained with 0.5% of detection limit. The error in calibration expressed with root mean square error of calibration was 0.979%. In addition, the error obtained during cross validation was 2.45%. A discriminant analysis test was able to distinguish between fries samples adulterated with lard and samples, which were pre-fried with palm oils. Fourier transform infrared spectroscopy is a fast and powerful technique for quantification of lard present in French fries.      

漫反射红外光谱法结合PLS测定稻谷脂肪酸值研究

为了快速、简便、无污染地测定稻谷中脂肪酸含量,提出基于漫反射傅里叶变换红外光谱法(DRIFTS)和近红外漫反射光谱法(NIDRS)测定稻谷脂肪酸值快速检测方法。同时探讨了反向区间偏最小二乘法(BiPLS)对中红外光谱区域的优化效果。傅里叶变换原始光谱模型经7点平滑预处理及BiPLS优化,得到的最佳模型的R~2、RMSECV、RMSEP分别为0.998、3.65、3.69。近红外光谱经一阶导数和多元散射校正预处理后建立最佳模型,其R~2为0.97,RMSECV为3.43。在验证实验中,傅里叶变换红外光谱预测值与国标测定值的相对标准偏差为1.16%,近红外光谱预测值与国标测定值的相对标准偏差为1.70%。结果表明,DRIFTS能够更加准确检测脂肪酸值。     

Direct determination of lactulose in heat‐treated milk using diffuse reflectance infrared Fourier transform spectroscopy and partial least squares regression

The aim of this work was the direct determination of lactulose (LCT) concentration in freeze‐dried heat‐treated milks using diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) without any chemical pretreatment of the milk. The ‘actual’ lactulose concentrations estimated by means of high‐performance liquid chromatography (HPLC) were correlated with the spectral region 1286–754 cm^?1 of DRIFTS spectra in the second‐derivative form of the milk samples using partial least squares (PLS) regression. A linear relationship was established between the ‘actual’ and the concentrations recalculated using the built model. The proposed DRIFTS method is simple, rapid and low cost.     

Determination of Total Sugar Content in Soy-Based Drinks Using Infrared Spectroscopy and Chemometrics

Partial least square (PLS) regression models were developed and compared in order to determine the total sugar content in soy-based drinks using an infrared spectroscopy technique known as attenuated total reflectance Fourier transform infrared (ATR-FTIR). On a spectrophotometer set for analyzing on the middle infrared region, spectral band of 1900 to 900 cm^?1, commercial samples of soy beverage were analyzed, as well as samples with crescent water additions of 5, 10, and 20% v/v. Reference data for total sugars were obtained using the Lane-Eynon method. To construct regression models, algorithms of interval partial least square (iPLS) and synergy of interval partial least square (siPLS) were applied using iToolbox package on Matlab 8.1 environment. Kennard-Stone algorithm was used to the selection of calibration and prediction sets. Two models have been the best obtained: the first was an iPLS with seven latent variables, which selected the spectral band of 1399–900 cm^?1 and presented root mean square error of cross-validation (RMSECV)?=?0.1678% (w/w). The second best model was siPLS with six latent variables, which selected spectral bands of 1025–1150 and 1151–1476 cm^?1 and presented RMSECV?=?0.1963% (w/w). The proposed method presents advantages such as a small-required amount of sample for spectrum achievement, no sample destruction, and a high analytical frequency.     

Identification and differentiation of goat and sheep milk based on diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) using cluster analysis

A new methodology for identification and differentiation of goat and sheep milk was developed based on FT-IR spectroscopy using hierarchical and discriminant analysis. Forty-nine goat and 38 sheep defatted and freeze-dried Greek milk samples were analyzed. FT-IR spectra were obtained in the diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) mode. The spectral region 1840–950 cm⁻¹ was used to ‘fingerprint’ milk types. Main peak used for differentiation of goat/sheep milk is located at 1745 cm⁻¹, which is correlated to the degree of sugars carboxyl methyl esterification. Hierarchical and discriminant analyses were based on the absorptions of the above spectral region. These analyses showed that the samples of goat milk can be differentiated from the samples of sheep’s.     

Use of Fourier Transform Infrared Spectroscopy in Combination with Partial Least Square for Authentication of Black Seed Oil

Fourier transform infrared spectroscopy in combination with multivariate calibration of partial least square is intended for quantitative analysis of black seed oil in binary mixture with sunflower oil and walnut oil, as well as in ternary mixture with sunflower oil and walnut oil. The spectra of black seed oil, sunflower oil, walnut oil, and their mixture with certain concentration were scanned using attenuated total reflectance at mid infrared region of 4000–650 cm^?1. For quantitatve analysis, Fourier transform infrared spectral treatment (normal or derivatives) with the highest values of coefficient of determination (R²) and the lowest values of root mean square error of calibration was selected as optimal calibration model. Partial least square at whole mid infrared region of 4000–650 cm^?1 is well suited for quantitative analysis of black seed oil either in binary mixture or ternary mixture with walnut oil and sunflower oil. Furthermore, using absorbancies at frequency region of 3009–721 cm^?1, principal component analysis is succesfully used for classification of black seed oil and that mixed with sunflower oil and walnut oil. The developed method is rapid, no sample preparation needed, and is not involving the use of chemical reagents and solvents.     

食醋总酸近红外快速检测方法的研究

利用傅立叶变换近红外光谱技术结合偏最小二乘法（PLS）对食醋的总酸进行快速检测分析。随机采集106个不同酸度食醋的实验数据、扫描近红外光谱图,选择最优的光谱预处理方法优化、建立模型。利用模型对15个未参与建模的食醋样品总酸的含量进行预测,外部验证模型的准确性。结果表明,食醋总酸实测值与对应采集的近红外漫反射光谱相关联建立的快速检测模型,其近红外食醋总酸模型的交叉验证决定系数（R2）为0.972 3,交叉验证均方差（RMSECV）为0.062 1。经外部验证后,该模型食醋总酸预测值和实测值的绝对偏差平均值为0.035,最大相对误差为1.383%,两者间相关性系数为0.995。该方法可以快速、高效、简便地用于食醋总酸的快速检测。     

Mid-infrared spectroscopy as a tool for rapid determination of internal quality parameters in tomato

The objective of this study was to investigate the possibility of predicting the quality parameters of tomato by mid-infrared spectroscopy. For 2 years, tomato samples, representing a large variability in the chemical composition, were scanned using the attenuated total reflectance accessory of a Fourier transform spectrometer in the wavenumber region between 4000 and 400 cm⁻¹_. Calibration models were developed using partial least squares (PLS) regression method and were tested with internal validation sample set in the first year. Different spectral preprocessing techniques were investigated and different spectral regions were selected to optimise the calibration models. In addition, the models obtained in 2007 were used to predict the soluble solids, dry matter and total acidity in tomato harvested in 2008.     

FTIR-ATR Spectroscopy Based Metabolite Fingerprinting as A Direct Determination of Butter Adulterated With Lard

Adulteration of butter with cheaper animal fats, such as lard, has become an issue in recent years. A simple and rapid analytical method of attenuated total reflectance in Fourier transform infrared spectroscopy was developed in order to determine the lard content in butter. The multivariate calibration of partial least square model for the prediction of adulterant was developed for quantitative measurement. The model yielded the highest regression with the correlation coefficient (R²) = 0.999, its lowest root mean square error estimation = 0.0947, and its root mean square error prediction = 0.0687, respectively. Cross validation testing evaluates the predictive power of the model. Partial least square model to be effective as their intercept of R²Y and Q²Y were 0.08 and –0.34, respectively.     

Rapid Determination of Spinal Cord Content in Ground Beef by Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy

ABSTRACT: The potential of attenuated total reflectance Fourier transform infrared spectroscopy to measure spinal cord in ground beef was investigated. Mid‐infrared spectra were obtained for ground beef adulterated with 0 to 100 ppm spinal cord. Partial least squares models were developed using 400 to 4000 cm^‐1. The model in the 400 to 4000 cm‐1 range showed a calibration of R_call= 0.94 (RMSE = 11.24) and validation of R_val= 0.87 (RMSE = 17.22). The P‐O‐C and N‐H stretches were found to correlate positively with spinal cord content. Fourier transform infrared spectroscopy has the potential to rapidly determine spinal cord adulteration in ground beef.     

FT-NIR spectroscopy coupled with multivariate analysis for detection of starch adulteration in turmeric powder

This paper investigates the feasibility of Fourier transform near-infrared (FT-NIR) spectroscopy, a fast and easy method based on chemometric methods to detect corn starch illegally added to turmeric powder. In this work, the pure turmeric powders were blended with corn starch to generate different concentrations (1–30%)(w/w) of starch-adulterated turmeric samples. The reflectance spectra of total of 224 samples were taken by FT-NIR spectroscopy. The exploratory data analysis was done by principal component analysis (PCA). The starch related peaks were selected by variable importance in projection (VIP) method and were explored by examination of original reflectance spectra, 1^st derivative spectra, PCA loadings and β coefficients plot of the partial least square regression (PLSR) model. The coefficient of determination (R²) and root-mean-square error of partial least square regression (PLSR) models were found to be 0.91–0.99 and 0.23–1.3%, respectively, depending on the pre-processing techniques of spectral data. The figure of merit (FOM) of the model was found with the help of net analyte signal (NAS) theory.     

Rapid estimation and quantification of sucrose content in fruit juices using Fourier transform infrared–attenuated total reflectance (FTIR–ATR) spectroscopy

An uncomplicated and rapid procedure has been developed for the quantitative analysis of sucrose in fruit samples (grape, pineapple, mango) through attenuated total reflectance–Fourier transform infrared absorbance measurements (ATR–FTIR). FTIR analysis takes considerably reduced time compared to the other classical methods. To calibrate the method, we used firstly, different concentrations of pure sucrose (from 1 to 5 %) and registered their IR maximal wavenumbers and peak intensity. The spectral peak of sucrose for each sample lies between 1057 and 1061 cm^?1. DNS method was used to analyse the content of sucrose by using spectrophotometry. The wave length used for analysing is 540 nm. Also high performance liquid chromatography was used to analyse the sucrose content in the fruit juices. By comparing the retention time of sucrose standards and the sample juices, sucrose concentration was identified and quantified. The results of all three experiments/techniques support each other by justifying that the mango has the high content of sucrose followed by pineapple and grape.     

Evaluation of the potential of FTIR and chemometrics for separation between defective and non-defective coffees

The objective of this work was to evaluate the potential of Fourier transform infrared spectroscopy (FTIR) for the discrimination of defective and non-defective coffee beans. Defective (black, immature and sour) and non-defective Arabica coffee beans were submitted to FTIR analysis by transmittance readings employing KBr discs and reflectance readings employing attenuated total reflectance (ATR) and diffuse reflectance (DR) accessories. Multivariate statistical analysis (PCA, clusters) was performed in order to verify the possibility of discrimination between defective and non-defective coffee samples. A clear separation between defective and non-defective coffee beans was observed, based on both PCA and cluster analysis of the reflectance spectra (ATR and DR accessories) and of the first derivatives of the transmittance spectra (KBr discs). Such results indicate that FTIR analysis has the potential for the development of a fast and reliable analytical methodology for the discrimination between defective and non-defective coffee beans.     

基于衰减全反射傅里叶变换红外光谱的餐饮废油掺假检测

为了建立基于衰减全反射傅里叶变换红外光谱(ATR-FTIR)的餐饮废油掺假检测方法,以常见食用油和餐饮废油为原料,收集8个餐饮废油和25个食用油样品,制备30个掺假油样品,共63个油样进行红外光谱扫描。随机取48个油样作为校正集样品,15个油样作为验证集样品,建立餐饮废油定性分析模型,并对定性模型进行验证;从30个掺假油样品中,随机取20个油样作为校正集样品,10个油样作为验证集样品,建立餐饮废油定量分析模型,并对定量模型进行验证。结果表明:在红外光谱范围为1 550~650 cm-1条件下,采用原始光谱结合判别分析建立定性分析模型,其识别率可达100%;采用偏最小二乘法(PLS)建立定量分析模型,在掺假比例1%~10%时,模型预测值与实际掺假比例呈良好的线性关系,相关系数(R)为0.982 2,标准偏差(SD)为0.47。表明基于ATR-FTIR的餐饮废油掺假检测是可行的。     

Mid-infrared spectroscopy and chemometrics for determining the type of fruit used in jam

Fourier transform infrared spectra of jams were analysed by chemometric methods with the aim of differentiating between ‘strawberry’ and ‘non-strawberry’ containing jams. Spectra were subjected to a data reduction step, which was either principal component analysis (PCA)-based or partial least squares (PLS)-based, before being classified in one of the two jam types on the basis of the smaller distance to the group ‘means’. Diffuse reflectance infrared spectra of the insoluble materials of the jams led to a success in classification of almost 100%. However, the preparation method was lengthy and still needs some improvement. Attenuated total reflectance spectra of jams were classified according to fruit type with 91% success. This method was found to be strongly influenced by the spectral differences between ‘normal’ and ‘reduced’ total sugar content jams, which appeared in the first principal component in both the PCA-based and the PLS-based method.     

Antioxidant potential of crocins and ethanol extracts of Gardenia jasminoides ELLIS and Crocus sativus L.: A relationship investigation between antioxidant activity and crocin contents

Crocins are water-soluble carotenoids responsible for the colour of saffron and gardenia. In this study, we isolated and identified three major crocins from gardenia, and then evaluated their antioxidant potential using four in vitro antioxidant tests in comparison with saffron ethanol extract (SE), gardenia ethanol extract (GE) and gardenia resin fraction (GRF). The relationship between total crocin contents and antioxidant activity of ethanol extracts of two herbs was investigated and the antioxidant potentials of three different polar crocins were compared. The crocins appeared to possess antioxidant activity when tested by four in vitro antioxidant models. However, in anti-hemolysis, DPPH radical-scavenging and lipid peroxidation assays, GRF exhibited significantly stronger antioxidant activity than crocins and no correlation between total crocin contents and antioxidative function was revealed, which implied that ingredients other than crocins in gardenia gave markedly strong antioxidant activity. In the phosphomolybdenum assay, antioxidant capacities of fractions and extracts correlated with total crocin contents (R = 0.93). Moreover, comparison of results indicated that sugars attached to the crocetin moiety seemed to be beneficial for the antioxidant activity of these water-soluble pigments.     

Determination of polygalacturonic acid content in pectin extracts by diffuse reflectance Fourier transform infrared spectroscopy

A simple, rapid diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) method was developed for pectin measurement. Pectin calibration standards were prepared by blending polygalacturonic acid with potassium bromide to cover a range of polygalacturonic acid concentrations (10–98%). A linear relationship between pectin content and total carbonyl absorption band area was found (R²=0.982). Linearity was up to 80% pectin, since there was no significant difference in peak areas of 80% and greater. Pectin contents of various commercial pectin samples were calculated from the linear fit equation. Accuracy of the DRIFTS method was determined by comparing the pectin contents to the values obtained by colorimetric and HPLC methods. For four different sources of samples, the pectin contents by FTIR method were 78.2, 89.4, 65.9 and 67.1%, which were comparable to values obtained by colorimetric analysis (79.1, 87.9, 64.7 and 57.7%) and HPLC (84.1, 91.4, 69.5 and 67.9%).