Magdalena Witek - Academia.edu (original) (raw)

Papers by Magdalena Witek

Acta Physica Polonica A, Mar 1, 2006

Proton exchange between spin groups of the solid matrix of hydrated granular potato starch and wa... more Proton exchange between spin groups of the solid matrix of hydrated granular potato starch and water was studied using the 2D time domain NMR. The proton spin-spin relaxation time T2, and spin-lattice relaxation time T 1 (selective and non-selective pulse sequences) were measured at room temperature. The observed spin relaxation results were analysed for exchange assuming a two-site exchange model (between water and solid matrix of starch). In this analysis we determined the intrinsic spin-lattice relaxation time for water protons (49 ms) and solid starch matrix protons (172 ms), as well as the water-starch magnetization exchange rate (86 s −1).

Journal of Magnetic Resonance, Dec 1, 2010

Assuming dipole-dipole interaction as the dominant relaxation mechanism of protons of water molec... more Assuming dipole-dipole interaction as the dominant relaxation mechanism of protons of water molecules adsorbed onto macromolecule (biopolymer) surfaces we have been able to model the dependences of relaxation rates on temperature and frequency. For adsorbed water molecules the correlation times are of the order of 10(-5)s, for which the dispersion region of spin-lattice relaxation rates in the rotating frame R(1)(ρ)=1/T(1)(ρ) appears over a range of easily accessible B(1) values. Measurements of T(1)(ρ) at constant temperature and different B(1) values then give the "dispersion profiles" for biopolymers. Fitting a theoretical relaxation model to these profiles allows for the estimation of correlation times. This way of obtaining the correlation time is easier and faster than approaches involving measurements of the temperature dependence of R(1)=1/T(1). The T(1)(ρ) dispersion approach, as a tool for molecular dynamics study, has been demonstrated for several hydrated biopolymer systems including crystalline cellulose, starch of different origins (potato, corn, oat, wheat), paper (modern, old) and lyophilized proteins (albumin, lysozyme).

Acta Physica Polonica A, 2020

Preliminary studies on the application of NMR relaxation measurements for observations of the kin... more Preliminary studies on the application of NMR relaxation measurements for observations of the kinetics of oxidation processes in tea samples were performed. Tea is a rich source of flavonoids and other compounds with great antioxidant capacity and is therefore beneficial for human health. Its antioxidant potential depends on the type of tea and the method of preparation. Green and black tea prepared from tea bags brewed in water at 90 • C for 20 and 60 min were examined. Oxidation processes were induced in tea samples by adding 3% H2O2 in 1:10 proportion. Observed time courses of spin-lattice T1 relaxation time and parameters obtained from fitting of combined exponential and compressed-exponential function, depended on kind of tea, brewing time, and milk addition. The obtained results showed the usefulness of the NMR relaxation measurements for observation of oxidation processes and antioxidant activity.

Journal of Magnetic Resonance, Sep 1, 2008

The water proton relaxation rate constant R 1 = 1/T 1 (at 60 MHz) of blood serum is substantially... more The water proton relaxation rate constant R 1 = 1/T 1 (at 60 MHz) of blood serum is substantially increased by the presence of free Cu 2+ ions at concentrations above normal physiological levels. Addition of chelating agents to serum containing paramagnetic Cu 2+ nulls this effect. This was demonstrated by looking at the effect of adding a chelating agent-D-penicillamine (D-PEN) to CuSO 4 and CuCl 2 aqueous solutions as well as to rabbit blood serum. We propose that the measurement of water proton spin-lattice relaxation rate constants before and after chelation may be used as an alternative approach for monitoring the presence of free copper ions in blood serum. This method may be used in the diagnosis of some diseases (leukaemia, liver diseases and particularly Wilson's disease) because, in contrast to conventional methods like spectrophotometry which records the total number of both bound and free ions, the proton relaxation technique is sensitive solely to free paramagnetic ions dissolved in blood serum. The change in R 1 upon chelation was found to be less than 0.06 s À1 for serum from healthy subjects but greater than 0.06 s À1 for serum from untreated Wilson's patients.

Acta Physica Polonica A, 2006

Proton exchange between spin groups of the solid matrix of hydrated granular potato starch and wa... more Proton exchange between spin groups of the solid matrix of hydrated granular potato starch and water was studied using the 2D time domain NMR. The proton spin-spin relaxation time T2, and spin-lattice relaxation time T 1 (selective and non-selective pulse sequences) were measured at room temperature. The observed spin relaxation results were analysed for exchange assuming a two-site exchange model (between water and solid matrix of starch). In this analysis we determined the intrinsic spin-lattice relaxation time for water protons (49 ms) and solid starch matrix protons (172 ms), as well as the water-starch magnetization exchange rate (86 s −1).

Polymers, 2021

Experimental protocols aiming at the characterisation of glass transition often suffer from ambig... more Experimental protocols aiming at the characterisation of glass transition often suffer from ambiguity. The ambition of the present study is to describe the glass transition in a complex, micro heterogeneous system, the dry rice pasta, in a most unambiguous manner, minimising the influence of technique-specific bias. To this end, we apply an unprecedented combination of experimental techniques. Apart from the usually used NMR and DSC, we employ, in a concurrent manner, neutron transmission, diffraction, and Compton scattering. This enables us to investigate the glass transition over a range of spatio-temporal scales that stretches over seven orders of magnitude. The results obtained by neutron diffraction and DSC reveal that dry rice pasta is almost entirely amorphous. Moreover, the glass transition is evidenced by neutron transmission and diffraction data and manifested as a significant decrease of the average sample number density in the temperature range between 40 and 60 °C. At t...

Journal of Dairy Science, 2020

The present research was established to study the effect of green tea and Pu-erh tea (PT) additiv... more The present research was established to study the effect of green tea and Pu-erh tea (PT) additives on the mechanical and hydration properties of yogurt gels using a combination of nuclear magnetic resonance, rheological, and textural studies. Tea infusions (0-15 mL/100 mL) were added to batch milk before fermentation with yogurt culture. Obtained dairy products were analyzed for the water mobility and organization, viscosity, and texture profile. Results of the rheological and nuclear magnetic resonance studies suggested that stabilization of the yogurt gel structure was achieved upon supplementation with tea infusions. Generally, green tea fortification produced yogurts with more consolidated gel structure, tighter interacting water, and less susceptibility to shearing and temperature changes than PT treatments. In contrast, PT yogurts were more viscous and characterized by 8 to 17% lower hardness values. This knowledge can be useful for developing novel dairy products with desired structure and consistency.

Food Hydrocolloids, 2020

Abstract In this study red currant was used as a source of pectin. The aim of this study was to i... more Abstract In this study red currant was used as a source of pectin. The aim of this study was to investigate the physicochemical properties of obtained polysaccharide, with an emphasis on behaviour in aqueous solutions. Pectin was obtained using water extraction, then the basic characteristics of the obtained polysaccharide was performed (FT-IR-ATR, molar mass distribution, sugar composition, DE). An applied extraction method resulted in a water-soluble pectin fraction with M w = 1020 kg ⋅ mol-1 and D E = 57 . 1 % . To study the behaviour of pectins in aqueous solutions various methods were used: membrane osmometry, viscosity measurements, rheology, NMR and DLS. The obtained results allowed to describe pectin chains properties in both dilute and semi-dilute regimes, including c ∗ value determination. Osmotic tests indicated low water affinity and strong intermolecular interactions for red currant pectin. Viscosity measurements revealed strong polyelectrolyte behaviour, initially the reduced viscosity of the solutions decreased, until the overlap concentration ( c ∗ = 0 . 78 g ⋅ dL-1) was reached and then increased sharply. Comprehensive interpretation of the results obtained by means of used methods allowed to conclude that red currant pectin takes the form of tightly wound coils in dilute solutions, with increasing concentration chains tending to expand and intermolecular interactions are being enhanced, which result in the formation of complex structures.

Annual Reports on NMR Spectroscopy, 2010

Time-domain NMR is being used throughout all areas of food science and technology. A wide range o... more Time-domain NMR is being used throughout all areas of food science and technology. A wide range of one- and two-dimensional relaxometric and diffusometric applications have been implemented on cost-effective, robust and easy-to-use benchtop NMR equipment. Time-domain NMR applications do not only cover research and development but also quality and process control in the food supply chain. Here the opportunity to further downsize and tailor equipment has allowed for “mobile” sensor applications as well as online quality inspection. The structural and compositional information produced by time-domain NMR experiments requires adequate data-analysis techniques. Here one can distinguish model-driven approaches for hypothesis testing, as well as explorative multi-variate approaches for hypothesis generation. Developments in hardware and software will further enhance measurement speed and reveal more detailed structural features in complex food systems.

Journal of Magnetic Resonance, 2010

Assuming dipole-dipole interaction as the dominant relaxation mechanism of protons of water molec... more Assuming dipole-dipole interaction as the dominant relaxation mechanism of protons of water molecules adsorbed onto macromolecule (biopolymer) surfaces we have been able to model the dependences of relaxation rates on temperature and frequency. For adsorbed water molecules the correlation times are of the order of 10(-5)s, for which the dispersion region of spin-lattice relaxation rates in the rotating frame R(1)(ρ)=1/T(1)(ρ) appears over a range of easily accessible B(1) values. Measurements of T(1)(ρ) at constant temperature and different B(1) values then give the "dispersion profiles" for biopolymers. Fitting a theoretical relaxation model to these profiles allows for the estimation of correlation times. This way of obtaining the correlation time is easier and faster than approaches involving measurements of the temperature dependence of R(1)=1/T(1). The T(1)(ρ) dispersion approach, as a tool for molecular dynamics study, has been demonstrated for several hydrated biopolymer systems including crystalline cellulose, starch of different origins (potato, corn, oat, wheat), paper (modern, old) and lyophilized proteins (albumin, lysozyme).

Food Research International, 2012

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright

Food Chemistry, 2010

The impact of heat-treatment on structure and hydration properties of rice was studied at differe... more The impact of heat-treatment on structure and hydration properties of rice was studied at different length scales (μm–nm). Heat-treatment introduced micro- and macro-pores within rice kernels (μCT) and, within intact cell walls, disintegrated starch granules were observed (SEM, CSLM). In native kernels starch predominantly occurred as crystalline A-type starch and, upon heat treatment, amorphous and V-type starch appeared (XRD, 13C

Journal of Magnetic Resonance, 2008

Acta Physica Polonica A, Mar 1, 2006

Proton exchange between spin groups of the solid matrix of hydrated granular potato starch and wa... more Proton exchange between spin groups of the solid matrix of hydrated granular potato starch and water was studied using the 2D time domain NMR. The proton spin-spin relaxation time T2, and spin-lattice relaxation time T 1 (selective and non-selective pulse sequences) were measured at room temperature. The observed spin relaxation results were analysed for exchange assuming a two-site exchange model (between water and solid matrix of starch). In this analysis we determined the intrinsic spin-lattice relaxation time for water protons (49 ms) and solid starch matrix protons (172 ms), as well as the water-starch magnetization exchange rate (86 s −1).

Journal of Magnetic Resonance, Dec 1, 2010

Assuming dipole-dipole interaction as the dominant relaxation mechanism of protons of water molec... more Assuming dipole-dipole interaction as the dominant relaxation mechanism of protons of water molecules adsorbed onto macromolecule (biopolymer) surfaces we have been able to model the dependences of relaxation rates on temperature and frequency. For adsorbed water molecules the correlation times are of the order of 10(-5)s, for which the dispersion region of spin-lattice relaxation rates in the rotating frame R(1)(ρ)=1/T(1)(ρ) appears over a range of easily accessible B(1) values. Measurements of T(1)(ρ) at constant temperature and different B(1) values then give the "dispersion profiles" for biopolymers. Fitting a theoretical relaxation model to these profiles allows for the estimation of correlation times. This way of obtaining the correlation time is easier and faster than approaches involving measurements of the temperature dependence of R(1)=1/T(1). The T(1)(ρ) dispersion approach, as a tool for molecular dynamics study, has been demonstrated for several hydrated biopolymer systems including crystalline cellulose, starch of different origins (potato, corn, oat, wheat), paper (modern, old) and lyophilized proteins (albumin, lysozyme).

Acta Physica Polonica A, 2020

Preliminary studies on the application of NMR relaxation measurements for observations of the kin... more Preliminary studies on the application of NMR relaxation measurements for observations of the kinetics of oxidation processes in tea samples were performed. Tea is a rich source of flavonoids and other compounds with great antioxidant capacity and is therefore beneficial for human health. Its antioxidant potential depends on the type of tea and the method of preparation. Green and black tea prepared from tea bags brewed in water at 90 • C for 20 and 60 min were examined. Oxidation processes were induced in tea samples by adding 3% H2O2 in 1:10 proportion. Observed time courses of spin-lattice T1 relaxation time and parameters obtained from fitting of combined exponential and compressed-exponential function, depended on kind of tea, brewing time, and milk addition. The obtained results showed the usefulness of the NMR relaxation measurements for observation of oxidation processes and antioxidant activity.

Journal of Magnetic Resonance, Sep 1, 2008

The water proton relaxation rate constant R 1 = 1/T 1 (at 60 MHz) of blood serum is substantially... more The water proton relaxation rate constant R 1 = 1/T 1 (at 60 MHz) of blood serum is substantially increased by the presence of free Cu 2+ ions at concentrations above normal physiological levels. Addition of chelating agents to serum containing paramagnetic Cu 2+ nulls this effect. This was demonstrated by looking at the effect of adding a chelating agent-D-penicillamine (D-PEN) to CuSO 4 and CuCl 2 aqueous solutions as well as to rabbit blood serum. We propose that the measurement of water proton spin-lattice relaxation rate constants before and after chelation may be used as an alternative approach for monitoring the presence of free copper ions in blood serum. This method may be used in the diagnosis of some diseases (leukaemia, liver diseases and particularly Wilson's disease) because, in contrast to conventional methods like spectrophotometry which records the total number of both bound and free ions, the proton relaxation technique is sensitive solely to free paramagnetic ions dissolved in blood serum. The change in R 1 upon chelation was found to be less than 0.06 s À1 for serum from healthy subjects but greater than 0.06 s À1 for serum from untreated Wilson's patients.

Acta Physica Polonica A, 2006

Proton exchange between spin groups of the solid matrix of hydrated granular potato starch and wa... more Proton exchange between spin groups of the solid matrix of hydrated granular potato starch and water was studied using the 2D time domain NMR. The proton spin-spin relaxation time T2, and spin-lattice relaxation time T 1 (selective and non-selective pulse sequences) were measured at room temperature. The observed spin relaxation results were analysed for exchange assuming a two-site exchange model (between water and solid matrix of starch). In this analysis we determined the intrinsic spin-lattice relaxation time for water protons (49 ms) and solid starch matrix protons (172 ms), as well as the water-starch magnetization exchange rate (86 s −1).

Polymers, 2021

Experimental protocols aiming at the characterisation of glass transition often suffer from ambig... more Experimental protocols aiming at the characterisation of glass transition often suffer from ambiguity. The ambition of the present study is to describe the glass transition in a complex, micro heterogeneous system, the dry rice pasta, in a most unambiguous manner, minimising the influence of technique-specific bias. To this end, we apply an unprecedented combination of experimental techniques. Apart from the usually used NMR and DSC, we employ, in a concurrent manner, neutron transmission, diffraction, and Compton scattering. This enables us to investigate the glass transition over a range of spatio-temporal scales that stretches over seven orders of magnitude. The results obtained by neutron diffraction and DSC reveal that dry rice pasta is almost entirely amorphous. Moreover, the glass transition is evidenced by neutron transmission and diffraction data and manifested as a significant decrease of the average sample number density in the temperature range between 40 and 60 °C. At t...

Journal of Dairy Science, 2020

The present research was established to study the effect of green tea and Pu-erh tea (PT) additiv... more The present research was established to study the effect of green tea and Pu-erh tea (PT) additives on the mechanical and hydration properties of yogurt gels using a combination of nuclear magnetic resonance, rheological, and textural studies. Tea infusions (0-15 mL/100 mL) were added to batch milk before fermentation with yogurt culture. Obtained dairy products were analyzed for the water mobility and organization, viscosity, and texture profile. Results of the rheological and nuclear magnetic resonance studies suggested that stabilization of the yogurt gel structure was achieved upon supplementation with tea infusions. Generally, green tea fortification produced yogurts with more consolidated gel structure, tighter interacting water, and less susceptibility to shearing and temperature changes than PT treatments. In contrast, PT yogurts were more viscous and characterized by 8 to 17% lower hardness values. This knowledge can be useful for developing novel dairy products with desired structure and consistency.

Food Hydrocolloids, 2020

Abstract In this study red currant was used as a source of pectin. The aim of this study was to i... more Abstract In this study red currant was used as a source of pectin. The aim of this study was to investigate the physicochemical properties of obtained polysaccharide, with an emphasis on behaviour in aqueous solutions. Pectin was obtained using water extraction, then the basic characteristics of the obtained polysaccharide was performed (FT-IR-ATR, molar mass distribution, sugar composition, DE). An applied extraction method resulted in a water-soluble pectin fraction with M w = 1020 kg ⋅ mol-1 and D E = 57 . 1 % . To study the behaviour of pectins in aqueous solutions various methods were used: membrane osmometry, viscosity measurements, rheology, NMR and DLS. The obtained results allowed to describe pectin chains properties in both dilute and semi-dilute regimes, including c ∗ value determination. Osmotic tests indicated low water affinity and strong intermolecular interactions for red currant pectin. Viscosity measurements revealed strong polyelectrolyte behaviour, initially the reduced viscosity of the solutions decreased, until the overlap concentration ( c ∗ = 0 . 78 g ⋅ dL-1) was reached and then increased sharply. Comprehensive interpretation of the results obtained by means of used methods allowed to conclude that red currant pectin takes the form of tightly wound coils in dilute solutions, with increasing concentration chains tending to expand and intermolecular interactions are being enhanced, which result in the formation of complex structures.

Annual Reports on NMR Spectroscopy, 2010

Time-domain NMR is being used throughout all areas of food science and technology. A wide range o... more Time-domain NMR is being used throughout all areas of food science and technology. A wide range of one- and two-dimensional relaxometric and diffusometric applications have been implemented on cost-effective, robust and easy-to-use benchtop NMR equipment. Time-domain NMR applications do not only cover research and development but also quality and process control in the food supply chain. Here the opportunity to further downsize and tailor equipment has allowed for “mobile” sensor applications as well as online quality inspection. The structural and compositional information produced by time-domain NMR experiments requires adequate data-analysis techniques. Here one can distinguish model-driven approaches for hypothesis testing, as well as explorative multi-variate approaches for hypothesis generation. Developments in hardware and software will further enhance measurement speed and reveal more detailed structural features in complex food systems.

Journal of Magnetic Resonance, 2010

Assuming dipole-dipole interaction as the dominant relaxation mechanism of protons of water molec... more Assuming dipole-dipole interaction as the dominant relaxation mechanism of protons of water molecules adsorbed onto macromolecule (biopolymer) surfaces we have been able to model the dependences of relaxation rates on temperature and frequency. For adsorbed water molecules the correlation times are of the order of 10(-5)s, for which the dispersion region of spin-lattice relaxation rates in the rotating frame R(1)(ρ)=1/T(1)(ρ) appears over a range of easily accessible B(1) values. Measurements of T(1)(ρ) at constant temperature and different B(1) values then give the "dispersion profiles" for biopolymers. Fitting a theoretical relaxation model to these profiles allows for the estimation of correlation times. This way of obtaining the correlation time is easier and faster than approaches involving measurements of the temperature dependence of R(1)=1/T(1). The T(1)(ρ) dispersion approach, as a tool for molecular dynamics study, has been demonstrated for several hydrated biopolymer systems including crystalline cellulose, starch of different origins (potato, corn, oat, wheat), paper (modern, old) and lyophilized proteins (albumin, lysozyme).

Food Research International, 2012

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright

Food Chemistry, 2010

The impact of heat-treatment on structure and hydration properties of rice was studied at differe... more The impact of heat-treatment on structure and hydration properties of rice was studied at different length scales (μm–nm). Heat-treatment introduced micro- and macro-pores within rice kernels (μCT) and, within intact cell walls, disintegrated starch granules were observed (SEM, CSLM). In native kernels starch predominantly occurred as crystalline A-type starch and, upon heat treatment, amorphous and V-type starch appeared (XRD, 13C

Journal of Magnetic Resonance, 2008