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Non-destructive inspection of food and technical oils by terahertz spectroscopy
摘要： Quality control and non-destructive monitoring are of notable interest of food and pharmaceutical industries. It relies on the ability of non-invasive inspection which can be employed for manufacturing process control. We hereby apply terahertz (THz) time-domain spectroscopy as non-destructive technique to monitor pure and degraded oils as well as hydrocarbon chemicals. Significant differences in the spectra of refractive index (RI) and absorption coefficient arising from the presence of ester linkages in the edible and technical oils were obtained. Explicit increase from 1.38 to 1.5 of the RI in all THz spectrum range was observed in hydrocarbons and mono-functional esters with the increase of molar mass. This fact is in contrast of RI dependence on molar mass in multi-functional esters, such as Adipate or vegetable oils, where it is around 1.54. Degradation products, Oleic Acid (OA) and water in particular, lead only to some changes in absorption coefficient and RI spectra of vegetable oils. We demonstrate that complex colloidal and supramolecular processes, such as dynamics of inverse micelles and oil hydrolysis, take part during oil degradation and are responsible for non-uniform dependence of optical properties on extent of degradation.
关键词： absorption coefficient,terahertz spectroscopy,oils,degradation,non-destructive inspection,refractive index
更新于2025-09-23 15:23:52
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Light-Responsive Nanocapsule-Coated Polymer Films for Antimicrobial Active Packaging
摘要： The development of antimicrobial active packaging constitutes a powerful tool to reduce waste and increase quality standards of perishable goods. Among numerous available antimicrobial agents, essential oils stand out for their renowned efficiency, and their use is beneficial due to their sustainability compared to other oil-based antimicrobials. In this work, we report on the use of photo-responsive nanocapsules containing thyme essential oil as functional coatings for polyethylene and polylactic acid films to obtain antimicrobial active packaging. Polymer surface activation treatment enhanced compatibility with nanocapsules solution. The films were analyzed to assess the structural and functional properties of the coating, evaluate morphological changes due to their photo-responsive behavior, and monitor the light-induced release of volatile thyme oil. It was found that 24 h after a 15-min UV exposure of the coated films, the concentration of thyme oil in the headspace was eight times higher with respect to un-irradiated films, thus confirming the efficiency of the light-triggered release system. Therefore, the manufactured films are proposed as on-demand release devices for application in non-contact antimicrobial active packaging.
关键词： antimicrobials,active packaging,coatings,essential oils,photo-responsive nanocapsules
更新于2025-09-23 15:22:29
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Rapid assessment of monovarietal Portuguese Extra Virgin Olive Oil's (EVOO's) fatty acids by Fourier-transform Near-Infrared Spectroscopy (FT-NIRS)
摘要： A rapid method for the evaluation of fatty acids (FA) of monovarietal Portuguese extra virgin olive oils (EVOO) (n = 82) from Alentejo, south-central region of Portugal, was developed based on Fourier-transform near-infrared spectroscopy (FT-NIRS). The contents of FA-components (previously determined per conventional gas chromatography) were correlated with FT-NIRS data (independent variable), by means of full cross-validation partial least squares regression (CVPLSR). CVPLSR was run using standard normal variate (SNV) data pre-processing and nonlinear iterative partial least squares (NIPALS) algorithm. Obtained correlation models were characterized with good statistics: high correlation coefficients (R > 0.85) and low root mean square errors (RMSE < 2.04). Obtained values of the residual predictive deviation (RPD) of CVPLSR-model, higher than 5.0 (C18:1, C18:2, MUFA, PUFA) confirmed the FT-NIRS as a potential method for rapid quality control of EVOO’s FA.
关键词： Extra virgin olive oils,fatty acids,CVPLSR,chemometrics,FT-NIRS
更新于2025-09-23 15:22:29
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Characterization of essential oils extracted from different aromatic plants by FTIR spectroscopy
摘要： Four essential oils isolated from dried leaves of parsley, lovage, basil and thyme were investigated by FTIR spectroscopy. The analysis of recorded spectra revealed that the main compounds of tested essential oils dominate their vibrational spectra.
关键词： dried leaves,essential oils,FTIR analysis,aromatic plants
更新于2025-09-23 15:22:29
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Rapid quantification of clove (Syzygium aromaticum) and spearmint (Mentha spicata) essential oils encapsulated in a complex organic matrix using an ATR-FTIR spectroscopic method
摘要： Essential oils (EOs) are often encapsulated in various and complex matrices to protect them against potential degradation or to control their release. To achieve an optimum use in food products, their rapid and precise quantification after encapsulation and storage is required. Hence, a rapid ATR-FTIR method was developed and tested with two encapsulated essential oils (EOs): clove (Syzygium aromaticum) and spearmint (Mentha spicata);. Despite, the complexity of the matrix, this method coupled with univariate or multivariate regression models exhibited high potential for global quantification of the two encapsulated EOs. For clove EO, in relation to the major presence of eugenol and eugenol acetate, an analysis based on a unique band (1514 cm-1) was sufficient to obtain a good prediction with RMSEP value of 0.0173 g of EO per g of matrix. For spearmint oil which is characterized by numerous terpenoid compound, three bands (799, 885, and 1680–1676 cm-1) were suitable for a good prediction with RMSEP value of 0.0133. ATR-FTIR method was compared with a reference gas chromatography FID quantitative method in an EO release experiment and its efficiency was evaluated through modeling by the Avrami equation. Beside time saving, the ATR-FTIR method was also capable of monitoring the EO profile. This method could be easily adapted as a routine analysis in the EOs industry as quality control.
关键词： Encapsulation,ATR-FTIR,Spearmint,Essential oils,Quantification,Clove
更新于2025-09-23 15:21:21
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Application of laser backscattering imaging for the physico-chemical characterisation of antimicrobial silica particles functionalised with plant essential oils
摘要： The capacity of orthogonal imaging applied to laser-backscattering for characterising antimicrobial particles based on immobilised essential oils was tested. Different particles were synthesised using various particle and oils. Samples were characterised physico-chemically and by an imaging technique. The technique recorded the generated patterns because of the laser-particles interaction during the sedimentation process. The series of images were transformed into an orthogonal image. Data extraction varied depending on the fragmentation degree of image length. After the multivariate analysis, the physico-chemical results showed variability due to particle size. That variability diminished the effect of oils for large sizes. The imaging data collected these properties, which could be used to recognise both particle size and oil type. Thus the prediction of the properties was successful. The position in the physico-chemical space of variance was also predicted. Hence this technique could complement a low-cost method to evaluate the properties of functionalised particles with oils.
关键词： Essential oils,Silica particles,Laser backscattering,Orthogonal imaging,Physico-chemical characterisation
更新于2025-09-23 15:21:01
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Monitoring of Microwave-Assisted Acid-Catalyzed Transesterification for Biodiesel Production Using FT-NIR Spectroscopy with Continuous-Flow Cell
摘要： The homogeneous microwave-assisted sulfuric acid-catalyzed transesterification of soybean oil, waste Brazil nut oil, sunflower oil and chicken fat for ethylic and methylic biodiesel production is described herein. The experiments were carried out in pilot-scale multimode reactors. The effects of the alcohol to oil molar ratio, catalyst concentration and irradiation time on the conversion to biodiesel were investigated. The transesterification reactions were performed at relatively small alcohol to oil molar ratios (9:1, 8:1 and 6:1) affording near 100% of conversion in reaction times of 60 to 120 min. Partial least squares (PLS) regression analysis using FT-NIR spectroscopy was performed to monitor the progress of the acid-catalyzed methanolysis of soybean oil. The NIR spectra were collected during the transesterification reaction with a spectrophotometric continuous-flow cell. 1H NMR spectroscopy was employed to determine the conversion percentage and used as a reference to build the PLS calibration model employing NIR spectroscopy data.
关键词： vegetable oils,sulfuric acid,FT-NIR spectroscopy,Animal fat,homogeneous acid catalysis,microwave-induced transesterification
更新于2025-09-23 15:21:01
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Variable selection for the determination of total polar materials in fried oils by near infrared spectroscopy
摘要： Total polar materials (TPM) content is considered as the best indicator and the most common parameter to check the quality of deep-frying oils. The development of simpler and quicker analytical techniques than the available methods to monitor oil quality in restaurants and fried food outlets is an important topic related to the human health. This paper reports a comparison of the variable selection of near infrared (NIR) spectra by multiple linear regression (MLR-NIR) with partial least squares (PLS-NIR) models for the quantification of TPM in fried vegetable oils. The use of PLS-NIR offers an alternative in laboratory bench equipment for the determination of TPM in oils employed for frying different kinds of foods with relative prediction errors of 6.5%, a coefficient of determination for prediction of 0.99 and a residual predictive deviation (RPD) of 9.2 when selected wavenumber intervals were employed. MLR-NIR allows the selection of a reduced number of wavenumber in order to develop low cost instruments to evaluate the frying oil quality. Based on the NIR signals at four wavenumbers, the relative prediction error was 12.1%, the coefficient of determination for prediction was 0.96 and the RPD was 5.0.
关键词： partial least squares,total polar materials,multiple linear regression,vegetable fried oils,Near infrared spectroscopy
更新于2025-09-23 15:21:01
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The First Identification of the Uniqueness and Authentication of Maltese Extra Virgin Olive Oil Using 3D-Fluorescence Spectroscopy Coupled with Multi-Way Data Analysis
摘要： The potential application of multivariate three-way data analysis techniques, namely parallel factor analysis (PARAFAC) and discriminant multi-way partial least squares regression (DN-PLSR), on three-dimensional excitation emission matrix (3D-EEM) fluorescent data were used to identify the uniqueness and authenticity of Maltese extra virgin olive oil (EVOO). A non-negativity constrained PARAFAC model revealed that a four-component model provided the most appropriate solution. Examination of the extracted components in mode 2 and 3 showed that these belonged to different fluorophores present in extra virgin olive oil. Application of linear discriminate analysis (LDA) and binary logistic regression analysis on the concentration of the four extracted fluorophores, showed that it is possible to discriminate Maltese EVOOs from non-Maltese EVOOs. The application of DN-PLSR provided superior means for discrimination of Maltese EVOOs. Further inspection of the extracted latent variables and their variable importance plots (VIPs) provided strong proof of the existence of four types of fluorophores present in EVOOs and their potential application for the discrimination of Maltese EVOOs.
关键词： extra virgin olive oils,DN-PLSR,Maltese islands,PARAFAC,3D-fluorescence
更新于2025-09-23 15:19:57
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Influence of Sample Mixing Techniques on Engine Oil Contamination Analysis by Infrared Spectroscopy
摘要： For the most reliable and reproducible results for calibration or general testing purposes of two immiscible liquids, such as water in engine oil, good emulsi?cation is vital. This study explores the impact of emulsion quality on the Fourier transform infrared (FT-IR) spectroscopy calibration standards for measuring water contamination in used or in-service engine oil, in an attempt to strengthen the speci?c guidelines of ASTM International standards for sample preparation. By using different emulsi?cation techniques and readily available laboratory equipment, this work is an attempt to establish the ideal sample preparation technique for reliability, repeatability, and reproducibility for FT-IR analysis while still considering the ease and ef?ciency of the technique. This study demonstrates that a stable emulsion within a sample, which depends heavily upon the method, provides a reliably consistent homogenous sample for quanti?cation purposes with FT-IR analysis. Analysis of variance (ANOVA) modeling and limit of detection calculations demonstrate the stability of the emulsion. The results reveal that setting a mixing time for a calibration standard depends on the emulsi?cation process. Inserting a probe directly into a sample (direct sonication) allows for a rapid, stable emulsion with high reproducibility. Indirect sonication produces relatively non-miscible liquids of different densities. The pan-shaker produces a reasonably stable emulsion, but without the long-term stability or quick production time of direct sonication. Reaction time plays a critical role in the rotary mixing method, which leads to a slow development of emulsi?cation.
关键词： mixing methods,lubricating oils,emulsion,water contamination,infrared spectroscopy
更新于2025-09-19 17:15:36