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Published By De Gruyter Open Sp. Z O.O.

1337-978x, 1337-978x

2021 ◽  
Vol 14 (1) ◽  
pp. 25-31
Author(s):  
Svetlana Schubertová ◽  
Zuzana Burčová ◽  
Mária Greifová ◽  
Marianna Potočňáková ◽  
Lívia Janotková ◽  
...  

Abstract The aim of the article was to investigate the effect of sea buckthorn juice addition on the growth of microbial cultures in growth medium and juice mixtures. Pure sea buckthorn juice was found to inhibit the growth of all 11 monitored microbial cultures. Lactobacillus plantarum CCM 7039, Lactobacillus plantarum K816, Lactobacillus brevis CCM 1815 and, to a lesser extent, the probiotic strain Lactobacillus rhamnosus GG, grew in a growth medium containing a 25 % addition of sea buckthorn juice. Lactobacillus plantarum K816 and Lactobacillus brevis CCM 1815 grew better in this mixture than in pure growth medium. Moreover, we focused on finding a suitable ratio of sea buckthorn and apple juice for Lactobacillus plantarum CCM 7039, leading to malolactic fermentation, which results in an increase in the pH value and an improvement in the sensory properties of juices. The intention was to incorporate the highest possible addition of sea buckthorn juice while maintaining the viability of Lactobacillus plantarum CCM 7039 for malolactic fermentation to occur. The best results were achieved using 40 % sea buckthorn juice. Practical application of the results points to the possibility of preparing a fermented fruit beverage and a dairy product containing sea buckthorn juice. The results of this work extend the current options of sea buckthorn juice processing increasing thus the consumption of healthy juice.


2021 ◽  
Vol 14 (1) ◽  
pp. 14-24
Author(s):  
Abdul Wasim Noori ◽  
Mohammad Jafar Royen ◽  
Juma Haydary

Abstract This study investigates the effect of ambient conditions change on mint leaves solar drying performance and product water activity. Two drying methods, active indirect solar drying (AISD) and open sun drying (OSD) were compared while the experiments were carried out at specific dry climate conditions. During the experimental days, temperature varied from 20 to 30 °C, air relative humidity from 14 to 28.8 % and ambient pressure was around 82 kPa. The effect of air relative humidity change during the day on the rehydration of the product during the drying process was observed. After 7 h of drying, moisture content of mint leaves decreased from 85.29 % to 5.38 % in the AISD and 7.42 % in the OSD system. The 0.97 initial water activity decreased to 0.195 in AISD and 0.79 in OSD. Rehydration during the evening hours caused an increase in product water activity from 0.2 to 0.51. Changes of ambient conditions such as temperature and air relative humidity during the day can significantly affect water activity of dried product due to its rehydration and thus increase the risk of product spoilage.


2021 ◽  
Vol 14 (1) ◽  
pp. 7-13
Author(s):  
Denisa Cagardová ◽  
Martin Michalík ◽  
Vladimír Lukeš

Abstract Gas-phase geometry and electronic structure of lumichrome, 1-methyl-lumichrome and lumiflavin in the electronic ground state and their excited states were investigated using the Density Functional Theory. Their binding ability with thymine was estimated for model van der Waals dimers with two intermolecular hydrogen bonds. The influence of hydrogen bonds on their photophysical properties was analyzed. Obtained theoretical data were compared with available experimental absorption and fluorescence spectra.


2021 ◽  
Vol 14 (1) ◽  
pp. 32-37
Author(s):  
Dagmar Štellerová ◽  
Vladimír Lukeš

Abstract Conformation analysis of dehydroascorbic acid and its bicyclic form was performed using the density functional theory. For the energetically preferred conformations, ionization potentials (IP) and bond dissociation enthalpies (BDE) were calculated using the B3LYP functional and 6-311++G** basis set. The effects of aqueous solution were estimated using the solvation model based on density (SMD) and the polarizable continuum model (IEF-PCM). The obtained results were compared with available experimental data for reference L-ascorbic acid (vitamin C). Our calculations indicate that the investigated bicyclic metabolic product of vitamin C can also exhibit limited radical scavenging ability due to the thermodynamically preferred dissociation of tertiary —CH bonds.


2021 ◽  
Vol 14 (1) ◽  
pp. 1-6
Author(s):  
Roman Košťúr ◽  
Matilda Zemanová

Abstract Corrosion layers of an iron artefact were characterized to study long-term exposition of iron in Slovakia. The iron artefact from Bratislava castle has been coated with a strong layer of corrosion products and masonry residues. Corrosion products were characterized by different methods including energy-dispersive X-ray spectroscopy (EDX), X-Ray diffraction (XRD), and µ-Raman Spectroscopy. Magnetite and goethite on the surface are confirmed typical corrosion products from long-term atmospheric exposure in environment with corrosivity category C-2 (low).


2021 ◽  
Vol 14 (1) ◽  
pp. 38-50
Author(s):  
Martin Breza

Abstract The relation between copper atomic charges and metal-ligand interaction energies obtained by PM6 and DFT-B3LYP methods for cytotoxicity prediction of model rutile nanoparticles [Ti40O124H81]7–, [Ti7O28H26]2–, [Ti2O10H10]2–, [Ti7O30H30]2– and their Cu(II) complexes is investigated. Except for Mulliken charges, very good statistical parameters were obtained for the linear relation between the results obtained by both methods if standard accuracy of quantum-chemical calculations is achieved.


2020 ◽  
Vol 13 (2) ◽  
pp. 38-48
Author(s):  
Miriama Šimunková ◽  
Michal Malček

Abstract Dimethyl sulfoxide (DMSO) is an aprotic organic solvent widely used in laboratory practice due to its ability to dissolve both polar and nonpolar compounds. However, DMSO is also commonly known as a strongly coordinating solvent, especially towards transition metal containing complexes. In this study, estimation of the coordination ability of DMSO towards the Cu(II) ion was attempted, employing a model system composed of 3′,4′-dihydroxyflavone-Cu(II) complex in the presence of explicit DMSO molecules, using the density functional theory (DFT). Nature of the Cu-DMSO chemical interaction (i.e. Cu-O bonding) was studied within the framework of quantum theory of atoms in molecules (QTAIM). Impact of DMSO coordination on the charge and spin distribution at Cu(II) ion was inspected using Mulliken population and QTAIM analysis.


2020 ◽  
Vol 13 (2) ◽  
pp. 30-37
Author(s):  
Anna Matejčíková ◽  
Pavol Rajniak

Abstract This work aimed to determine the effect of packing density on the sublimation rate in a laboratory freeze dryer. Total amount of sublimed water was determined by gravimetric method while a total of seven experiments were performed under the same conditions (pressure, temperature, and drying time), at different configuration of the vials. The experiments confirmed that the higher the packing density, the lower the drying rate, and vice versa, the lower the packing density, the higher the drying rate. The effect of vials packing density was confirmed by experiments using a plastic rack, while the vials were separated and thus the packing density was lower. In this case, the drying rate was more homogeneous, which contributes to the higher quality of the final product.


2020 ◽  
Vol 13 (1) ◽  
pp. 88-97
Author(s):  
Michaela Skrizovska ◽  
Hana Veznikova ◽  
Petra Roupcova

AbstractThis paper focuses on the assessment of the inclination to self-ignition of various types of wood chips according to the methodology of European standard EN 15188. The study also assesses the effect of heating temperatures on the composition and quantity of gaseous products of heating. Gases were analysed using an infrared spectrometer with Fourier transformation. From the measured results it was found that the inclination to self-ignition differs for various samples of wood chips. The paper discusses certain parameters assumed to affect the inclination of biomass to self-ignite. When assessing the effect of temperature on the composition of gaseous products, a sample of forest wood chips heated at temperatures from 50 to 150 °C resulted in the following gaseous products: carbon dioxide, carbon monoxide, water and aliphatic hydrocarbons; their concentrations increase with the increasing temperature. Carbon oxides have been proposed as indicators of the state of stored materials self-heating. Observations presented in this paper can be used as data for elaborating safety instructions for storage of fuels based on solid biomass.


2020 ◽  
Vol 13 (1) ◽  
pp. 49-55
Author(s):  
Martin Michalík ◽  
Monika Biela ◽  
Denisa Cagardová ◽  
Vladimír Lukeš

AbstractSystematic quantum chemical investigation of quercetin and selected eight mono- and bihydroxyflavonols is presented. Structural analysis based on the Density Functional Theory showed that the energetically preferred conformation of flavonols substituted at the C5 and C3 atoms by a hydroxyl group is stabilised via intramolecular hydrogen bonds occurring between the (C4)O···HO(3 or 5) atomic pairs. Depending on the hydroxyl group positions, energetically preferred torsional orientation of the phenyl ring with respect to the planar benzo-γ-pyrone moiety changed from 0 to 180 degrees. Gas-phase electron transitions were investigated using the time-dependent DFT treatment. The dependence of maximal wavelengths on the torsional deformation of the phenyl ring is of a similar shape, i.e. minima observed for the perpendicular orientation and maxima for the planar one. Shape and energies of the Highest Occupied (HOMO) and Lowest Unoccupied (LUMO) Molecular Orbitals were compared. The obtained theoretical results were compared with available experimental data.


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