Aldona Krupska

Influence of heating time and pressure treatment of potato starch on the generation of radicals: EPR studies

The influence of heating time and pressurizing time under pressure of 1 GPa on radicals generation in potato starch polymer was investigated by EPR. Potato starch was heated at two temperatures: 413 ± 2 K (140 °C) and 473 ± 2 K (200 °C) for 15, 30, 60, 120, 180, 240, 270 and 300 min and subdued to pressurizing under pressure of 1 ± 0.002 GPa for 6, 60, 300 and 1440 min. In starch heated at 413 K (140 °C) a decrease in the relative intensity of the EPR signal as a function of the pressurizing time can be observed, whereas in starch heated at 473 K (200 °C) such a decrease is not observed. The EPR spectra analysis indicates that they are powder spectra due to the paramagnetic centers leading to Lorentzian line shapes with weak spectroscopic splitting factor g anisotropies and linewidth anisotropies. We have shown that pressurization of starch causes a decrease in the number of radicals in a temperature range in which the polymer is not yet disintegrated. The results of the EPR investigations indicate the existence of a carbon radical center situated at the carbon C1 of the glucose ring. In the EPR spectra of the samples heated with no oxygen access, the hyperfine structure is poorly visible. In the registered EPR spectra of the samples heated with oxygen access, the hyperfine structure is not observed.

Effect of temperature and high pressure on Mn2+ EPR spectra in K3H(SO4)2 fast-proton conductor

The linewidth ΔH pp and spin-Hamiltonian parameters under temperature and high hydrostatic pressure by X-band continuous wave electron paramagnetic resonance in the K3H(SO4)2 crystal were studied. Spin-Hamiltonian parameters, direction cosines and coordination of Mn2+ ion were determined at room temperature. The pressure at 300 MPa leads to the change of hydrogen bond potential and the transition from double well to single well potential moves about 10 K towards a higher temperature.

High pressure impact on changes in potato starch granules

Abstract Air dry potato starch (84.9% d.s.) was subjected to pressurizing under the pressure of 50, 100, 250, 500, 750, 1000 and 2000 MPa for 1 h. The physical properties of pressurized starch, such as morphology, surface and crystalline structure, gelatinization parameters, were studied by means of scanning and atomic force microscopy (SEM/AFM), X-ray diffraction (X-ray), differential scanning calorimetry (DSC). The susceptibility to the amylolytic enzyme (α-amylase) was also measured. Application of pressure in the range of 50–2000 MPa results in an increase in the compressed potato starch bulk density, change in the contours of the granules from oval to polyhedral, increase in the roughness of the granule surface, vanishing of the X-ray reflexes generated by the orthogonal structure and weakening of the reflexes generated by the hexagonal structure, lowering of the enthalpy of starch gelatinization, and the enhancement of hydrolytic susceptibility of starch granules to the amylolytic enzyme.

Study of the phase delay in the amplitude-modulated harmonic oscillator

The delayed response of a damped harmonic oscillator (RLC circuit) to a slow periodic disturbance is presented. This communication is supplementary to the paper published recently (Krupska et al 2001 Eur. J. Phys. 22 133–8).