Reginald H. Wilson

Fourier-Transform Raman and Fourier-Transform Infrared Spectroscopy (An Investigation of Five Higher Plant Cell Walls and Their Components)

Infrared and Raman spectra of sequentially extracted primary cell walls and their pectic polymers were obtained from five angiosperm plants. Fourier-transform Raman spectrometry was shown to be a powerful tool for the investigation of primary cell-wall architecture at a molecular level, providing complementary information to that obtained by Fourier-transform infrared microspectroscopy. The use of an extraction procedure using imidazole instead of cyclohexane trans-1,2-N,N,N[prime],N[prime]-diaminotetraacetate allows the extension of the infrared spectral window for data interpretation from 1300 to 800 cm-1, to 2000 to 800 cm-1, and allows us to obtain Raman spectra from extracted cell-wall material. Wall constituents such as pectins, proteins, aromatic phenolics, cellulose, and hemicellulose have characteristic spectral features that can be used to identify and/or fingerprint these polymers without, in most cases, the need for any physical separation. The Gramineae (rice [Oryza sativa], polypogon [Polypogon fugax steud], and sweet corn [Zea mays]) are spectroscopically very different from the nongraminaceous monocotyledon (onion [Allium cepa]) and the dicotyledon (carrot [Daucus carota]); this reflects differences in chemical composition and cross-linking of the walls. The possibility of a taxonomic classification of plant cell walls based on infrared and Raman spectroscopies and the use of spectral fingerprinting for authentication and detection of adulteration of products rich in cell-wall materials are discussed.

Hydration properties of xylan‐type structures: an FTIR study of xylooligosaccharides

An FTIR study of the effect of hydration as a function of relative humidity on the structurally different xylooligosaccharide models is presented. The IR spectral pattern changes are strongly affected by the type and position of the glycosidic linkages and reflects the hydration properties of the models.

Molecular interactions in bacterial cellulose composites studied by 1D FT-IR and dynamic 2D FT-IR spectroscopy.

Specific strain-induced orientation and interactions in three Acetobacter cellulose composites: cellulose (C), cellulose/pectin (CP) and cellulose/xyloglucan (CXG) were characterized by FT-IR and dynamic 2D FT-IR spectroscopies. On the molecular level, the reorientation of the cellulose fibrils occurred in the direction of the applied mechanical strain. The cellulose-network reorientation depends on the composition of the matrix, including the water content, which lubricates the motion of macromolecules in the network. At the submolecular level, dynamic 2D FT-IR data suggested that there was no interaction between cellulose and pectin in CP and that they responded independently to a small amplitude strain, while in CXG, cellulose and xyloglucan were uniformly strained along the sample length.

Quantitative analysis of potential adulterants of extra virgin olive oil using infrared spectroscopy

Abstract The determination of food authenticity and the detection of adulteration are problems of increasing importance in the food industry. This is especially so for ‘value-added’ products, where the potential financial rewards for substitution with a cheaper ingredient are high. In this paper, the potential of infrared spectroscopy as a rapid analytical technique for the quantitative determination of adulterants in extra virgin olive oil is demonstrated. The method uses Fourier transform infrared spectroscopy, combined with attenuated total reflectance and partial least squares regression. Model systems comprising two types of ‘contaminant’ oil — refined olive and walnut — are investigated.

Discrimination between Coffea arabica and Coffea canephora variant robusta beans using infrared spectroscopy

The seed or ‘bean’ of the coffee plant is an important crop, grown commercially across the world. Two species are commonly cultivated: Coffea arabica and Coffea canephora variant robusta. Analytical techniques for species identification, in particular of coffee products such as ground or ‘instant’ coffees, are of great importance. In this paper, mid-infrared spectroscopy is proposed as a rapid alternative to existing authentication methods, which are often time-consuming or difficult to implement successfully. A Fourier-transform infrared spectrometer is used for this work, equipped with a diffuse reflectance accessory. Statistical procedures comprising principal components analysis and classical discriminant analysis are applied to spectra of ground roast arabica and robusta beans, and results presented which demonstrate that the species of such samples can readily be identified.

Approaches to understanding the functional architecture of the plant cell wall.

Cell wall polysaccharides are some of the most complex biopolymers known, and yet their functions remain largely mysterious. Advances in imaging methods permit direct visualisation of the molecular architecture of cell walls and the modifications that occur to polymers during growth and development. To address the structural and functional relationships of individual cell wall components, we need to better characterise a broad range of structural and architectural alterations in cell walls, appearing as a consequence of developmental regulation, environmental adaptation or genetic modification. We have developed a rapid method to screen large numbers of plants for a broad range of cell wall phenotypes using Fourier transform infrared microspectroscopy and Principal Component Analysis. We are using model systems to uncover the genes that encode some of the cell-wall-related biosynthetic and hydrolytic enzymes, and structural proteins.

Chemical engineering applications of electrical process tomography

Electrical tomographic imaging has been applied to a broad range of chemical engineering processes, including: bubble columns, fluidised beds, pneumatic transport, liquid mixing, cyclonic separation, pressure filtration, liquid pipe-flow, polymerisation, emergency depressurisation, and paste extrusion. Two imaging approaches are described, electrical capacitance tomography (ECT) and electrical impedance tomography (EIT). To date, these have primarily been used as low-cost research tools for studying process dynamics, although they potentially may also act as sensors permitting on-line monitoring and control. Various aspects of design, operation and data processing are described, along with a review of applications in the literature.

Mid-infrared spectroscopy for food analysis: recent new applications and relevant developments in sample presentation methods

Abstract This article deals with recent developments in the use of mid-infrared (MIR) spectroscopy for the analysis of foods. It has become apparent that MIR can be used to address a wide range of issues and provide solutions for rapid analysis and on-line control. In parallel with the new applications to food, which include new qualitative and quantitative applications and discriminant (classification) methods, there have been several technical advances in other fields that are set to impact on the food sector. New applications of transmission methods are described, which have been particularly successful for the analysis of oils and fats. Despite new advances in other sampling techniques, transmission methods have been quite widely employed. Diffuse reflectance has also been used with some considerable success, with new accessory designs and applications in food authentication using chemometric methods. However, the largest number of new applications and technical developments have used attenuated total reflectance (ATR). Novel ATR cells have been designed for high-temperature, high-pressure and a range of on-line applications. ATR has been used for a wide range of analytical application. The analysis of sugars in various systems has been particularly well studied. The authors predict that the use of MIR spectroscopy is likely to continue to increase and develop in the near future.

Mid-infrared spectroscopy and authenticity problems in selected meats : a feasibility study

Abstract This paper describes the results of a feasibility study into the use of mid-infrared spectroscopy for addressing certain authenticity problems with selected fresh meats. Preliminary analyses for meat speciation, the detection of ‘frozen-thawed’ meat, and semi-quantitative analysis of meat mixtures are reported. Fourier transform mid-infrared spectroscopy, attenuated total reflectance sample presentation, principal component analysis and partial least squares regression were used. It was possible to distinguish minced chicken, pork and turkey meats from their infrared spectra, and for each meat species it was possible to differentiate between fresh and frozen-thawed samples. Mid-infrared spectroscopy was also able to semi-quantitatively measure the levels of turkey and pork mixed with chicken meat. The method, which is rapid and easy to use, could with further development have the potential for authentication and quality control of meat products.

Comparison of two infrared spectroscopic methods for cheese analysis.

Two infrared spectroscopic methods, optothermal near infrared (NIR) spectroscopy and Fourier transform mid-infrared-attenuated total reflection (FTIR-ATR) spectroscopy, were applied to 24 cheese samples in order to obtain protein, fat and moisture contents. Reference values of the protein, fat and moisture contents in weight percent were obtained using standard wet chemistry analysis. Prediction correlation coefficients between 0.93 and 0.96 and standard errors of prediction between 2% and 5% were obtained using optothermal spectroscopy while the corresponding values for FTIR-ATR were 0.81-0.92 and 4-9%. Inhomogeneities in the cheeses, primarily due to the fat droplets, are probably the main reason for the differences in the error sizes. The superior results for optothermal spectroscopy are the more attractive because the instrument is easier to use than the FTIR-ATR instrument, it provides results more quickly with simpler statistical analysis and it is more compact and robust.