Persona: Monago Maraña, Olga
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Publicación Fluorescence properties of flavonoid compounds. Quantification in paprika samples using spectrofluorimetry coupled to second order chemometric tools(Elsevier, 2016-04-01) Durán Merás, Isabel; Galeano Díaz, Teresa; Muñoz de la Peña, Arsenio; Monago Maraña, OlgaThe influence of pH on the fluorescence of flavonoid compounds was investigated and the highest fluorescence emission was obtained in basic medium. Selected conditions to improve this signal were: pH 9.5, 0.14 M Britton Robinson buffer and methanol between 5% and 10%. The excitation–emission fluorescence matrices of a set of 36 samples of Spanish paprika were analyzed by means of parallel factor analysis (PARAFAC). Thus, the profiles of possible fluorescence components (PARAFAC loadings) were obtained. One of these profiles was identified by matching PARAFAC scores with LC analysis on the same samples. Two clusters of samples were obtained when score values were plotted against each other. Spectrofluorimetry coupled to second order multivariate calibration methods, as unfolded-partial least squares with residual bilinearization (U-PLS/RBL) and multidimensional-partial least-squares with residual bilinearization (N-PLS/RBL), was investigated to quantify quercetin and kaempferol in those samples. Good results were obtained for quercetin by this approach.Publicación Non-destructive fluorescence spectroscopy combined with second-order calibration as a new strategy for the analysis of the illegal Sudan I dye in paprika powder(Elsevier, 2020-05) Eskildsen, Carl Emil; Muñoz de la Peña, Arsenio; Galeano Díaz, Teresa; Wold, Jens Petter; Monago Maraña, OlgaThis paper presents a novel strategy for determination of the illegal dye Sudan I in paprika powder. The method is based on fluorescence spectroscopy combined with second-order calibration, which was employed for the first time for this purpose. The method is non-destructive and requires no sample preparation. It was probed that Sudan I exhibited fluorescence; however, the color of paprika samples affected the signal and it was not possible to quantify this adulterant by means of univariate and first-order calibration. To model the effect of variability of color in samples, a central composite experimental design was performed with varying ASTA (American Spices Trade Association) color values and Sudan I concentrations. Different second-order algorithms were tried for quantification. The best results for calibration and validation were obtained from Unfolded-Partial Least-Squares (U-PLS) and Multi-way Partial Least-Squares (N-PLS). The level of detection ranges were 0.4 – 3 mg/g and 0.5 – 3 mg/g for U-PLS and N-PLS, respectively. This was lower than other methods found in the literature.Publicación Non-destructive Raman spectroscopy as a tool for measuring ASTA color values and Sudan I content in paprika powder(Elsevier, 2019-02-15) Eskildsen, Carl Emil; Afseth, Nils Kristian; Galeano Díaz, Teresa; Muñoz de la Peña, Arsenio; Wold, Jens Petter; Monago Maraña, OlgaThe aim of this study was developing a non-destructive method for the determination of color in paprika powder as well as for detecting possible adulteration with Sudan I. Non-destructive Raman spectroscopy was applied directly to paprika powder employing a laser excitation of 785 nm for the first time. The fluorescence background was estimated, by fitting a polynomial to each spectrum, and then subtracted. After preprocessing the spectra, some peaks were clearly identified as characteristic from pigments present in paprika. The preprocessed Raman spectra were correlated with the ASTA color values of paprika by partial least squares regression (PLSR). Twenty-five paprika samples were adulterated with Sudan I at different levels and the PLSR model was also obtained. The coefficients of determination (R2) were 0.945 and 0.982 for ASTA and Sudan I concentration, respectively, and the root mean square errors of prediction (RMSEP) were 8.8 ASTA values and 0.91 mg/g, respectively. Finally, different approaches were applied to discriminate between adulterated and non-adulterated samples. Best results were obtained for partial least squares – discriminant analysis (PLS-DA), allowing a good discrimination when the adulteration with Sudan I was higher than 0.5%.Publicación Determination of pungency in spicy food by means of excitation-emission fluorescence coupled with second-order chemometric calibration(Elsevier, 2018-04) Guzmán Becerra, María; Muñoz de la Peña, Arsenio; Galeano Díaz, Teresa; Monago Maraña, OlgaCapsaicinoids are a family of compounds responsible for the pungency of spicy foods. In this work, the combination of fluorescence and chemometrics was investigated as a novel quantification method of capsaicinoids in spicy food samples. The excitation–emission matrices (EEMs) of the two major capsaicinoids (capsaicin and dihydrocapsaicin) were identical. Hence, the results were presented as the total content of capsaicinoids. The EEMs of a group of paprika, cayenne and chilli peppers, and of another group of spicy sauces were registered. The decomposition of the EEMs of each group was performed by parallel factor analysis (PARAFAC), obtaining three principal components in each case. After the decomposition, the component corresponding to capsaicinoids was identified by comparison with the profile of a standard mixture of capsaicin and dihydrocapsaicin. In addition, the score values of this component were correlated with the Scoville heat units (SHU) calculated by means of an HPLC–FLD method. Good correlations were obtained in both groups (0.998 and 0.992), confirming the assignation of the component to capsaicinoids. Subsequently, a calibration set was built to carry out the calibration in the spectrofluorimeter, using PARAFAC and U-PLS/RBL as second-order calibration algorithms. Good results for SHU determination were obtained in both groups with both algorithms and when the fluorimetric method was validated by means of liquid chromatographic analysis the relative error of prediction was less than 11.3%.Publicación Untargeted classification for paprika powder authentication using visible – Near infrared spectroscopy (VIS-NIRS)(Elsevier, 2021-03) Eskildsen, Carl Emil; Galeano Díaz, Teresa; Muñoz de la Peña, Arsenio; Wold, Jens Petter; Monago Maraña, OlgaThis paper describes a non-destructive screening method for authentication of paprika belonging to the Spanish Protected Designation of Origin (PDO) “Pimentón de La Vera”. Different multivariate classification models were developed in order to differentiate PDO and non-PDO samples, using visible-near infrared spectra as fingerprint for each paprika sample. Sample treatment was not required. Principal component analysis (PCA) was applied in different spectral ranges: 400–2500, 400–800 and 800–2500 nm. In all spectral ranges, PCA was largely able to differentiate PDO from non-PDO samples. Partial least-squares - discriminant analysis (PLS-DA), PCA-linear discriminant analysis (LDA) and PCA-quadratic discriminant analysis (QDA) were used as classification methods in the different spectral ranges. All methods were able to differentiate PDO from non-PDO samples, with error rates (ER) lower than 0.15. The best models were those obtained with PLS-DA in the NIR range (800–2500 nm), showing ERs lower than 0.07 and error indexes (IERROR) (false positives) lower than 0.05.Publicación Monitoring of chlorophylls during the maturation stage of plums by multivariate calibration of RGB data from digital images(MDPI, 2022-12-22) Domínguez Manzano, Jaime; Muñoz de la Peña, Arsenio; Durán Merás, Isabel; Monago Maraña, Olga::virtual::3179::600; Monago Maraña, Olga; Monago Maraña, Olga; Monago Maraña, OlgaThe methodology developed in this study was based on digital imaging processing of plums harvested in eight different weeks during their ripening process. Mean RGB data, histograms, and matrices of RGB data were used to characterise the ripening stage of the plums, in both qualitative and quantitative approaches, by using classification and quantification chemometric methods. An exploratory analysis of data was performed using principal component analysis (PCA) and parallel factor analysis (PARAFAC) in RGB histograms and matrices data, respectively, showing differences in the colour features since the fourth week of harvesting. In the case of the quantitative approach, high correlation was achieved between the histogram data, using partial least squares (PLS), and total chlorophyll content. In addition, between three-way matrixes and total chlorophyll content, good correlations were obtained applying unfolded-PLS (U-PLS) and N-way-PLS (N-PLS). The most accurate results were obtained on the green channel. Analytical parameters obtained were good, with determination coefficients (R2) higher than 0.91 for all models in the first and second-order multivariate analysis. In addition, relative errors of prediction (REPs) were lower than 12% in all models for the green channel. Therefore, the proposed method was a satisfactory alternative to destructive physiological and biochemical methods in the determination of total chlorophylls in plum samples. In the routine analysis, first-order multivariate calibration with PLS analysis is a good option due to the simplicity of data processing.Publicación Analytical technique and chemometrics approaches in authenticating and identifying adulteration of paprika powder using fingerprints: a review.(Elsevier, 2022) Durán Merás, Isabel; Muñoz de la Peña, Arsenio; Galeano Díaz, Teresa; Monago Maraña, OlgaPaprika powder authentication has gained interest in recent decades along with increases in its consumption. There are different Protected Designation of Origins (PDOs) around the world, some of them are from Spain, and it is important to assure the quality parameters that they offer and to provide a guaranty about their quality and authentication. This review covers the latest advances concerning the targeted and untargeted methodologies. These methodologies have been developed to ensure paprika powder authenticity, corroborating that it belongs or not to a certain PDO and that it complies with the regulations and legal standards for its consumption, as well as detection of possible adulterations, mainly with Sudan dyes, which are illegal colorants. Differences between spectroscopic and non-spectroscopic methods have been emphasized. As observed from the literature, paprika powder has not been extensively studied, but the number of papers has been increasing in recent years.Publicación First-order discrimination of methanolic extracts from plums according to harvesting date using fluorescence spectra. Quantification of polyphenols(Elsevier, 2021-10) Cabrera Bañegil, Manuel; Lavado Rodas, Nieves; Muñoz de la Peña, Arsenio; Durán Merás, Isabel; Monago Maraña, OlgaFluorescence spectroscopy in combination with chemometric analysis was applied to discriminate between Japanese Angeleno variety of plums, according to the date of harvesting. Emission spectra (obtained from 280 to 500 nm, and from 345 to 500 nm, respectively) of methanolic extracts of plums at two excitation wavelengths (280 and 330 nm, respectively) were obtained. The fluorescence spectral data were firstly processed by Principal Component Analysis (PCA), as an exploratory study, to extract relevant information from the spectral data, and revealed differentiation between plum samples based in the harvested time. In addition, Partial Least-Squares-Discriminant-Analysis (PLS-DA) was used for the development of the classification models, allowing 100% accuracy to differentiate between the date of harvesting, independently that pulp or skin plum extracts were analyzed. Spectral patterns of plums showed significant differences during maturation period, with a special emphasis between the months of May and September. In addition, calibration models were obtained for different individual polyphenols with partial least-squares (PLS) regression, obtaining the best results for epicatechin and neochlorogenic acid determination.Publicación Chemometric Discrimination Between Smoked and Non-Smoked Paprika Samples. Quantification of PAHs in Smoked Paprika by Fluorescence-U-PLS/RBL(Springer Nature, 2016-10-10) Galeano Díaz, Teresa; Muñoz de la Peña, Arsenio; Monago Maraña, OlgaThis study presents a strategy for differentiating paprika obtained by means of different drying systems. The differentiation is performed using spectroscopic fluorescence in combination with multivariate analysis. The two groups of samples (smoked or non-smoked paprika) are classified according to the content of some of their fluorescent compounds presented in each group, among which several polycyclic aromatic hydrocarbons (PAHs) are included. These compounds are characteristic in smoked food. The full information of excitation–emission matrices (EEMs) is processed with the aid of unsupervised parallel factor analysis (PARAFAC), PARAFAC supervised by linear discriminant analysis (LDA) and discriminant unfolded partial least squares (DU-PLS). The last algorithm allows an adequate classification of unknown paprika samples. Besides, the quantification of several PAHs in paprika was performed by means of unfolded partial least squares with residual bilinearization (U-PLS/RBL). On this way, three (fluorene, phenantrene, and anthracene) out of the five (fluorene, phenantrene, anthracene, pyrene and chrysene) selected analytes were quantified.Publicación Four- and five-way excitation-emission luminescence-based data acquisition and modeling for analytical applications. A review(Elsevier, 2019-11-20) Alcaraz, Mirta R.; Goicoechea, Héctor C.; Muñoz de la Peña, Arsenio; Monago Maraña, OlgaThe latest advances in both theory and experimental procedures on third-order/four-way and fourth-order/five-way calibration methods are discussed. This report is focused on excitation–emission (fluorescence and phosphorescence) matrices generation, employing different variables as the third data mode (time retention in chromatography, pH gradient, fluorescence/phosphorescence lifetime, kinetics, or other chemical treatments). Fully capitalizing on the second-order advantage, it has been possible to develop appealing analytical applications in spite of the complexity of the data. Extraction of the significant chemical information about the system under study as well as the individual abundance of the contributing constituents after proper higher-order data decomposition has allowed to analytical researchers performing quantitative analysis of complex samples. The experimental works reported up to the present are introduced and discussed in order to illustrate concepts. Throughout this work, the analytical benefits achieved by modeling third- and fourth-order data are exposed, attempting to contribute to the ongoing debate in the chemometric community regarding the existence and the true nature of the third-order advantage.