András Salgó

Microwave extraction. A novel sample preparation method for chromatography.

The applicability of microwave irradiation to the extraction of various types of compounds from soil, seeds, foods and feeds as a novel sample preparation method for chromatography was investigated. Samples were ground and mixed with an appropriate solvent, methanol or methanol-water for polar compounds and hexane for non-polar compounds. The suspensions were irradiated for 30 s, but they were not allowed to boil. After cooling, the irradiation was repeated several times. The samples were then centrifuged, and aliquots of the supernatant were injected into a chromatographic column. The yields of the extracted compounds obtained by microwave irradiation were compared with those obtained by the traditional Soxhlet or shake-flask extraction methods. The microwave extraction method was more effective than the conventional methods. Due to the considerable savings in time and energy, this novel method is suitable for fast extractions of large sample series.

Effect of the degree of substitution of cyclodextrin derivatives on chiral separations by high-performance liquid chromatography and capillary electrophoresis

Optical isomers of some basic racemic drugs (oxprenolol, AMEBD, ephedrine) were separated by high-performance liquid chromatography (HPLC) and/or capillary electrophoresis (CE) using carboxymethyl-beta-cyclodextrin (CMBCD) with various degree of substitution (DS). The effects of the separation conditions (pH, concentration and DS of CMBCD) were studied and compared using CE and HPLC. The degree of substitution had a significant effect on the resolution of the optical isomers and the ionic strength of the separation media, hence the use of well characterized CD derivatives is crucial. Different optimum DS values for the same test samples were obtained when HPLC or CE was used.

Changes in moisture content during wheat maturation - What is measured by near infrared spectroscopy?

The aim of the present study was to detect maturation processes in wheat seed non-destructively with special respect to changes in moisture content and natural hydration/dehydration processes. Maturation is a phase of seed development in which a series of biochemical, enzymatic and morphological changes occur under highly hydrated conditions. The role of water is therefore critical to the whole maturation process. The amount and variation in content of different water species [high density water (HDW) with weaker hydrogen bonding and low density water (LDW) with stronger hydrogen bonding] changed considerably during maturation. Characteristic changes in three water absorption bands [1890–1920 nm (water I), 1400–1420 nm (water II) and 1150–1165 nm (water III)] were analysed. It was concluded that the different transitions of water molecules could be followed sensitively through different regions of NIR spectra. In the maturing seed, combination bands (water I and water III) were more sensitive indicators of changes in water molecules than was the first overtone (water II). The polar qualification system (PQS) provided sensitive and informative results regarding the amount and species of water in the developing seed. NIR spectroscopic techniques can be used effectively in monitoring plant physiological processes and the spectra have hidden information for predicting the stage of growth in wheat seed.

Characterisation of soils by the near infrared technique

There are physical, physico-chemical and chemical parameters which can be used as a basis for the characterisations of soils. Some of these characterisation methods are slow, laborious and show very empiric character. Near infrared (NIR) reflectance spectroscopic methods were used for substitution of conventional soil analysis procedures. Seven different soil characteristics (humus, calcium carbonate, total nitrogen, dead water content, yarn test by Arany, mechanical composition, hygroscopic water content) were measured by NIR using Hungarian and ISO standards as reference methods. It was concluded that the humus content, which measures the total organic content of soil can be predicted from NIR spectra with good accuracy (SEP = 0.3%). There are two parameters (mechanical composition and hygroscopicity) which showed significant correlation with the changes in the status of water in soil and they were detectable with acceptable accuracy based on their NIR spectra. The other four parameters were not predictable either due to the lack of spectroscopic information or to the poor quality of reference methods. The developed method was very sensitive to the physical status of samples and an accurate standard sample preparation was needed. Spectral libraries were developed and validated for a quick and non-destructive qualification and selection of soil samples.

Relationship between NIR spectra and RVA parameters during wheat germination

ABSTRACT The process of germination in six different wheat cultivars was monitored using NIR spectroscopy and the Rapid Visco Analyser (RVA) method. Near-infrared spectra provided insight into both chemical and physical changes that occur in the seed, in particular mobilization processes involving carbohydrates. RVA curves also contain physical and chemical information and can be interpreted as physicochemical spectra. The process of germination was followed sensitively through the RVA curves and some rheological parameters (peak viscosity, trough, breakdown, final viscosity, and setback) were highly correlated (R = 0.95–0.98) with predicted values calculated from NIR spectra. Viscosity data calculated from RVA curves collected at 200–480 sec showed the most characteristic changes during the early heat treatment stage of the pasting procedure. Strong intercorrelations were found between viscosity data and NIR spectra from the beginning of the swelling and gelatinization processes in germinating seed. The ...

Demonstration of an intramitochondrial invertase activity and the corresponding sugar transporters of the inner mitochondrial membrane in Jerusalem artichoke (Helianthus tuberosus L.) tubers

Genetic evidences indicate that alkaline/neutral invertases are present in plant cell organelles, and they might have a novel physiological function in mitochondria. The present study demonstrates an invertase activity in the mitochondrial matrix of Helianthus tuberosus tubers. The pH optimum, the kinetic parameters and the inhibitor profile of the invertase activity indicated that it belongs to the neutral invertases. In accordance with this topology, transport activities responsible for the mediation of influx/efflux of substrate/products were studied in the inner mitochondrial membrane. The transport of sucrose, glucose and fructose was shown to be bidirectional, saturable and independent of the mitochondrial respiration and membrane potential. Sucrose transport was insensitive to the inhibitors of the proton-sucrose symporters. The different kinetic parameters and inhibitors as well as the absence of cross-inhibition suggest that sucrose, glucose and fructose transport are mediated by separate transporters in the inner mitochondrial membrane. The mitochondrial invertase system composed by an enzyme activity in the matrix and the corresponding sugar transporters might have a role in both osmoregulation and intermediary metabolism.

Comparison of Different Types of NIR Instruments in Ability to Measure β-Glucan Content in Naked Barley

ABSTRACT Importance of β-glucan in human nutrition is mirrored in numerous approval applications registering β-glucan containing products as health beneficial products in accordance with forthcoming EU Health Claims Regulation. In comparison to other cereals, barley contains considerable amounts of β-glucan. Naked barley is of particular interest because it circumvents the costs and loss of beneficial substances related to dehusking. In this study, the potential of near-infrared spectroscopy as an accurate, fast and economic method of determination of β-glucan in naked barley was appraised. Four different near-infrared instruments were used to analyze 107 barley samples, in both whole grain and milled form. Importantly, both black and purple pericarp samples, which are of additional nutritional interest due to high anthocyanin content, and waxy samples, which show an extraordinary high β-glucan content could be analyzed within the same calibration set as the normal samples. All tested dispersive near-infr...

Simple Enzymic Methods for Prediction of Plant Protein Digestibility

For the investigation of the digestibility of plant proteins a two-digestive-enzyme /trypsin, pancreatin/ in vitro measuring technique was used in the pH-decrease and pH-stat methods respectively. Parallel to the in vitro measurement, true and apparent digestibility were investigated in in vivo experiments on rats. It was established from data obtained for 45 test proteins that results obtained with the pH-stat method in a digestive period of 10′ are closely correlated /r=0.91/ with in vivo data, digestibility can be well predicted from the in vitro data.

Changes in protein content during wheat maturation—what is measured by near infrared spectroscopy?

The amount and variation in content of different proteins changes considerably during maturation and these changes were non-destructively monitored in developing grain using near infrared (NIR) spectroscopy. Characteristic changes in two protein absorption bands were identified (2055–2065 nm, identified as amide A/II and 2175–2180 nm, identified as amide I/III) and it was concluded that the different dynamics of protein development (accumulation of proteins as well as gluten network formation) could be followed sensitively by monitoring these two different regions of NIR spectra. Amide A/II represents the effect of protein network formation during maturation based on the vibrations of inter-chain hydrogen bonded N–H groups in polypeptides. Amide I/III is the manifestation of protein accumulation, as in the formation of gliadins and glutenins that interact together to form a gluten network. NIR spectroscopy is shown to be effective in monitoring plant physiological processes both qualitatively and quantitatively, and the spectra have more hidden information for predicting the stage of growth in wheat seed.

Near-infrared reflectance and Fourier transform infrared analysis of instant coffee mixtures

Determination of the actual coffee content of coffee mixtures by wet analytical methods is lengthy and tedious. An alternative method was used, where coffee mixtures were prepared from instant coffee and instant coffee substitute within a range of 0–100% of actual coffee, 0–28.78 mg g–1 of caffeine and 0–25.77 mg g–1 of chlorogenic acid. The actual coffee, caffeine and chlorogenic acid contents were determined by near-infrared reflectance (NIR) and Fourier transform infrared (FT–IR) spectroscopic methods. Calibration was used to find the relationship between the spectra obtained and the coffee, caffeine and chlorogenic acid content. The integrated intensity in the range of 1900–1500 cm–1 in the analytical infrared region was recorded and values estimated by use of multiple linear regression and the partial least squares (PLS) method, in the case of NIR measurements, provided the basis for the calculations. The developed FT–IR and NIR methods were found to be reliable, rapid and exact for determining the actual coffee, caffeine and chlorogenic acid content of instant coffee mixtures within an acceptable level of accuracy.