Rytel E.,Wroclaw University of Environmental and Life Sciences
Food Control | Year: 2012
The aim of this experiment was the determination of glycoalkaloid and nitrate content in potatoes during stages of processing into dry potato dice.Samples obtained from the tubers of three potato varieties were used: a very early Denar variety of Polish origin; Innovator, an early Dutch variety; and a Polish medium early Pasat variety. There were sampled three times from the factory store in 2009 and 2010. The potatoes were diced in laboratory conditions, by first peeling with a carborundum peeler, dicing into 10 × 10 × 10 mm pieces and rinsing with water at a temperature of 20 °C. In the next stages, the diced potatoes were blanched in water at a temperature of 75 °C for 5 min then dried in a laboratory drier for 1 h at 120 °C. After 1 h of drying, the temperature was lowered to 55-60 °C in order to obtain a defined final moisture content of 8-11%.In the raw material, intermediates and finished products, the concentrations of glycoalkaloids (α-chaconine and α-solanine) were determined using an HPLC method, and nitrates were determined colorimetrically using an RQflex analyser.It was found that the processes used in dried potato dice production significantly decreased concentrations of glycoalkaloids (α-chaconine and α-solanine) in intermediate and finished products when compared to raw material. The highest decrease in the quantity of glycoalkaloids occurred during peeling (33%) and after blanching (17%) of peeled potato. Nitrate content fell the most after cutting and rinsing with water (13%), and after blanching (23%). On average, dry potato dice contained 44% of the initial quantity of glycoalkaloids and 40% nitrate content in the final dried product. © 2011 Elsevier Ltd.
Rohm W.,Wroclaw University of Environmental and Life Sciences
Atmospheric Research | Year: 2012
The GNSS signal passing through the layers of the atmosphere, including troposphere is subjected to many effects. One of the effect is a change of signal phase propagation speed due to the change of density. The large fluctuation of density is due to water vapor content - the most important greenhouse gas. The ground GNSS tomography is a tool to obtain the wet refractivity of the discrete model above the network of receivers. The wet refractivity could be converted into water vapor partial pressure, using the additional temperature information. This paper presents rigorous approach to obtain uncertainties of the final product - water vapor partial pressure in the voxel. All factors influencing the final uncertainty has been taken into account, mainly uncertainty of: Zenith Troposphere Delay, pressure, antenna phase center height, satellite elevation angle, mapping function, tomography solution and temperature. The analyzed error budget shows, great influence of cofactor matrix topology on tomography solution uncertainty. It is also shown that ground GNSS tomography is feasible to obtain water vapor partial pressure in the troposphere up to 0.5. hPa so in average 6. km above the ground. © 2012 Elsevier B.V.
Figiel A.,Wroclaw University of Environmental and Life Sciences
Journal of Food Engineering | Year: 2010
Beetroot cubes were dehydrated by convective drying in hot air at 60 °C and by the combination of convective pre-drying (CPD) until moisture content 1.6, 0.6 or 0.27 kg/kg db and vacuum-microwave finish drying (VMFD) at 240, 360 or 480 W. The control samples were obtained by freeze-drying (FD). The drying kinetics of beetroot cubes was described with an exponential function. VMFD significantly reduced the total time of drying and decreased drying shrinkage in comparison with convective method. A critical moisture content divided the temperature profile of samples during VMFD into increasing and falling periods. At the falling temperature period a significant increase in the colour parameters L*, a* and b* was found. VM treated samples as well as FD ones exhibited lower compressive strength, better rehydration potential and higher antioxidant activity than those dehydrated in convection. Increasing the microwave wattage and decreasing the time of CPD improved the quality of beetroot cubes dried by the combined method. © 2010 Elsevier Ltd. All rights reserved.
Becek K.,Wroclaw University of Environmental and Life Sciences
IEEE Transactions on Geoscience and Remote Sensing | Year: 2014
The accuracy of global digital elevation models (GDEMs or DEMs), i.e., the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Shuttle Radar Topography Mission (SRTM), has been reassessed using the 'runway' method. The runway method uses the vertical profiles of runways as reference data to which corresponding profiles extracted from investigated DEMs are compared. The major advantage of the runway method is that only the source of instrument-induced errors of DEMs is captured. This ultimate effect is achieved due to the flatness and the homogeneous materials from which runways are constructed. A cross-comparison of the two DEMs has helped to highlight a few important facts: both exhibit a negative elevation bias, and the ASTER DEM contains outliers that may be relatively easy to detect and correct, particularly in flat terrain. © 2013 IEEE.
Rohm W.,Wroclaw University of Environmental and Life Sciences
Advances in Space Research | Year: 2013
The GNSS signal along its more than 20,000 km line of sight is bended, attenuated and delayed. These effects are results of the Earth's atmosphere, and Sun radiation. Amongst all mentioned effects the one considered in this paper is a signal phase delay in troposphere. This paper presents investigations in the field of GNSS ground tomography, a remote sensing technique able to capture distribution of water vapour partial pressure in the troposphere. In this method, observations are Slant Wet Delays (SWD), the phase delay of GNSS signal due to the presence of water vapour in the troposphere. One of the most important limitation in GNSS tomography is so far mandatory usage of constraints to improve design matrix rank score and in consequence the ability to obtain meaningful troposphere parameters. Solution proposed here is based on combination of SWDs from several consecutive observation epochs to increase rank score. Another important goal is to perform careful selection of singular values in the process of pseudo inverse, to limit the observation noise influence. Three different methods to select singular values are investigated: functional analysis, significant testing and L-curve fitting. The obtained results are validated by means of internal uncertainties propagation, and comparison with external model. With the simulated data the unconstrained stacked GNSS produce reliable results with uncertainties on the level of 0.3hPa in terms of water vapour partial pressure and with mean discrepancies on the level of 0.1hPa. The same measures transform to the 0.03% and 0.01% of relative error on the ground level and 100% and more, above 8 km. Moreover all instabilities inside profiles were resolved properly. The simulations shows that to attain such optimistic results at least 10 observations epoch have to be stacked. © 2012 COSPAR. Published by Elsevier Ltd. All rights reserved.