5 research outputs found
Comparison of different methods of antioxidant activity evaluation of green and roast C. Arabica and C. Robusta coffee beans
Coffee beans contain a large amount of antioxidants, which are subjected to various changes during roasting. In this study, antioxidant potential of raw and roasted to different degree (light, medium, dark) C. arabica and C. robusta coffee beans was evaluated by the four antioxidant assay methods, TPC, FRAP, TEAC, and DPPHË™.
The obtained results revealed significant differences between the coffee types, roasting degree, and antioxidant activity assessment methods. FRAP and TPC appeared to be the most appropriate methods for revealing the differences in antioxidant potential of different coffee types and the effects of roasting. The results obtained by these methods were in good correlation. ABTS and DPPH? methods are not enough sensitive for the determination of roasting degrees.
In general, based on statistical data evaluation, antioxidant activity is more dependent on the coffee type than on the degree of roasting, however, the selection of analytical method may also be significant
Time- and energy-resolved effects in the boron-10 based Multi-Grid and helium-3 based thermal neutron detectors
The boron-10 based Multi-Grid detector is being developed as an alternative
to helium-3 based neutron detectors. At the European Spallation Source, the
detector will be used for time-of-flight neutron spectroscopy at cold to
thermal neutron energies. The objective of this work is to investigate fine
time- and energy-resolved effects of the Multi-Grid detector, down to a few
eV, while comparing it to the performance of a typical helium-3 tube.
Furthermore, it is to characterize differences between the detector
technologies in terms of internal scattering, as well as the time
reconstruction of ~ s short neutron pulses. The data were taken at the
Helmholtz Zentrum Berlin, where the Multi-Grid detector and a helium-3 tube
were installed at the ESS test beamline, V20. Using a Fermi-chopper, the
neutron beam of the reactor was chopped into a few tens of s wide pulses
before reaching the detector, located a few tens of cm downstream. The data of
the measurements show an agreement between the derived and calculated neutron
detection efficiency curve. The data also provide fine details on the effect of
internal scattering, and how it can be reduced. For the first time, the chopper
resolution was comparable to the timing resolution of the Multi-Grid detector.
This allowed a detailed study of time- and energy resolved effects, as well as
a comparison with a typical helium-3 tube.Comment: 37 pages, 21 figure