Repozitorij Univerze v Novi Gorici

Iskanje po repozitoriju
A+ | A- | Pomoč | SLO | ENG

Iskalni niz: išči po
išči po
išči po
išči po
* po starem in bolonjskem študiju

Opcije:
  Ponastavi


1 - 9 / 9
Na začetekNa prejšnjo stran1Na naslednjo stranNa konec
1.
2.
Chemical characterization of cider produced in hardanger : from juice to finished cider
Ingunn Ovsthus, Mitja Martelanc, Alen Albreht, Tatjana Radovanović Vukajlović, Urban Česnik, Branka Mozetič Vodopivec, 2024, izvirni znanstveni članek

Opis: Our investigation delves into the previously uncharted territory of cider composition from Norway. This study aimed to obtain an overview of the qualitative and quantitative compositions of general chemical parameters, polyphenols (individual and total expressed as gallic acids equivalents), selected esters, and selected C6-alcohols in ciders with the PDO label Cider from Hardanger. In total, 45 juice and cider samples from the fermentation process were collected from 10 cider producers in Hardanger in 2019, 2020, and 2021. Individual sugars, acids, ethanol, and 13 individual phenols were quantified using HPLC-UV/RI. Seven ethyl esters of fatty acids, four ethyl esters of branched fatty acids, ten acetate esters, two ethyl esters of hydroxycinnamic acids, and four C6-alcohols were quantified using HS-SPME-GC-MS. For samples of single cultivars (‘Aroma’, ‘Discovery’, ‘Gravenstein’, and ‘Summerred’), the sum of the measured individual polyphenols in the samples ranges, on average, from 79 to 289 mg L−1 (the lowest for ‘Summerred’ and highest for ‘Discovery’ and ‘Gravenstein’). Chlorogenic acid was the most abundant polyphenol in all samples. Ethyl butyrate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, ethyl isobutyrate, ethyl 2-methylbutyrate, isoamyl acetate, and hexanol were present at concentrations above the odour threshold and contributed to the fruity flavour of the Cider from Hardanger.
Ključne besede: cider, volatile aroma, esters, higher alcohols, polyphenols
Objavljeno v RUNG: 14.08.2024; Ogledov: 856; Prenosov: 6
.pdf Celotno besedilo (1,02 MB)
Gradivo ima več datotek! Več...

3.
Aromatic characterization of Graševina wines from Slavonia and Podunavlje sub-regions
Mitja Martelanc, Guillaume Antalick, Tatjana Radovanović Vukajlović, Branka Mozetič Vodopivec, Melita Sternad Lemut, Ahmad Hosseini, Valentina Obradović, Josip Mesić, Lorena Butinar, 2024, izvirni znanstveni članek

Opis: This study investigated the chemical aromatic profiles of 60 volatile organic compounds (VOCs), including 21 terpenes, 6 norisoprenoids, 6 volatile phenols, 4 C-6 alcohols, and 23 esters, in Graševina wines originating from Slavonia and Podunavlje sub-regions (Croatia). Headspace solid-phase microextraction gas chromatography coupled with mass spectrometric detection (HS-SPME-GCMS) was used to assess 60 VOCs, and a novel HS-SPME-GCMS method for the determination of terpenes and norisoprenoids was developed and validated. Statistical analysis also found no significant differences between VOCs present in Graševina wines and others wines (Chardonnay and Pinot gris); nonetheless, comparison of VOC fingerprints between different wines from the same producer showed that four terpenes (α-terpinene, γ-terpinene, 1,4-cineol, and 4-terpineol) were present in higher amounts in Graševina wines when compared to other wines. By exclusively examining VOCs within Graševina wines through the utilization of a heatmap and hierarchical clustering, a distinct visualization of samples and VOCs emerged, highlighting the vintage effect. Simultaneously, a partial least squares discriminant analysis model was developed with a confidence interval of 95%, demonstrating a noticeable distinction between samples originating from the western and eastern regions. Furthermore, by employing the heatmap using only VOCs from the terpene and norisoprenoidic groups, a clear separation of samples into two groups was observed based on geographical origin; namely, higher concentrations of norisoprenoids and terpenes were observed in the Slavonia sub-region. These results suggest that terpenes and norisoprenoids to a lower extent may be valuable aromatic markers for the regional typicality of Graševina wines.
Ključne besede: Graševina–Welschriesling, aromatic profiling, HS-SPME-GCMS, terpenes
Objavljeno v RUNG: 08.04.2024; Ogledov: 1642; Prenosov: 16
.pdf Celotno besedilo (12,58 MB)
Gradivo ima več datotek! Več...

4.
Chemical composition of apple cider : a comparative study of Norwegian and French ciders
Ingunn Ovsthus, Mitja Martelanc, Tatjana Radovanović Vukajlović, Marko Lesica, Lorena Butinar, Branka Mozetič Vodopivec, Guillaume Antalick, 2024, objavljeni znanstveni prispevek na konferenci

Opis: Norwegian apple ciders have recently gained attention at the levels of international competitiveness. Accordingly, a comparative study on the chemical composition of selected Norwegian and French apple ciders was conducted to gain knowledge on what ubiquitous chemical parameters make the Norwegian ciders different from ciders from well-established producing regions. A total of 43 ciders, 24 Norwegian and 19 French, in the category of acidic dominant ciders, were included in the study. Ethanol, individual sugars and organic acids, pH, total phenols, aroma compounds including esters, C6-alcohols, volatile phenols and terpenoids, were analysed. Norwegian ciders showed higher contents in ethanol, malic and citric acids, whereas total phenols, pH, glucose, and fructose were higher in French counterparts. Regarding the aromatic profile, no significant differences were observed for C6-alcohols. In contrast, differences were more expressed in the case of esters and volatile phenols. Norwegian ciders were characterised by higher average concentration for all the groups of esters, with the most important differences measured for higher alcohol acetates. Norwegian ciders also displayed higher contents of 4-vinylphenol and 4-vinylguaiacol while French ciders contained substantially higher levels of 4-ethylphenol and 4-ethylguaiacol. These results are in mutual correlation with the empirical observation reporting Norwegian apple ciders as more acidic, alcoholic and with lighter body but fruitier profile. Whereas French ciders are often perceived with more structure and animalistic profile.
Ključne besede: alcohol, acidity, total phenols, aroma-compounds, apple cider
Objavljeno v RUNG: 25.03.2024; Ogledov: 1793; Prenosov: 6
URL Povezava na datoteko
Gradivo ima več datotek! Več...

5.
6.
7.
Novel methods for detection of bioactive substances and their effects in organisms and in the environment
Tatjana Radovanović Vukajlović, doktorska disertacija

Opis: Since the concentration of bioactive substances and infectious agents in organisms and in the environment are low highly sensitive techniques such as: chromatography technology coupled with mass spectrometry (GC/MS, LC/MS and LC–MS/MS) and transmission electron microscopy (TEM) are needed for their detection. These techniques are highly sensitive, but time consuming, requiring use of expensive apparatus and large quantities of reagents and organic solvents which are harmful for the environment. Because there is a growing need for analysis of a large number of environmental samples it is necessary to develop new, so called vanguard methods that enable rapid and reliable screening of large numbers of samples in the shortest possible time. Analysis with such “screening” methods are often less accurate or even semi-quantitative, but nevertheless allow reliable identification of nonproblematic samples and in practice they limit the use of demanding classical analytical methods to only a few percent of all the samples. Therefore, general objectives of the thesis were development of novel methods for sensitive, fast and cost effective detection of pharmaceuticals, viruses and viral particles in waters and biological fluids and for detection of their effects in organisms. Novel methods were based on the combination of TLS (Thermal Lens Spectrometry), microfluidics and immunological methods such as ELISA. TLS as highly sensitive technique (allowing detection of absorbances of less than 10-6) coupled with microfluidic technology allows detection of very low analyte concentration, shorter time for analysis, higher sample throughput and low consumption of reagents. In such combination microfluidic technology can simplify or speed up antigen-antibody or enzyme-substrate interactions in bioanalytical systems. Decisive advantage of microfluidic systems lies in the fact that small dimensions of such systems, composed of capillaries and micro-reactors with dimensions from about 10 to 100 µm, significantly reduce diffusion time, which is inversely proportional to second power of distance. However, highly sensitive detection techniques are needed in microfludic systems, because the amounts of analytes in detection volumes are generally small and optical interaction lengths are two to three orders of magnitude shorter than in conventional spectrometric techniques. By combining microscopic TLS (TLM) with microfluidic technique it is possible to reach very low limits of detection and at the same time shorten ELISA analysis time from 20 h to 20 minutes as was described before in the literature for detection of BNP (brain natriuretic peptide). TLM furthermore allows measurements of extremely small volumes (sub-microliter) as well as fast signal response (milliseconds). In this Dissertation specific goals were the development of new methods for detection of selected bioactive substances and infectious agents: -iodinated contrast agents -NGAL (neutrophil gelatinase associated lipocalin) as a new biomarker of contrast induced nephropathy (CIN) -antibodies against human papilloma viruses (HPV) viruses and HPV-16 pseudovirions. For the development of new method for detection of iodinated contrast agents chemical degradation of iodinated contrast agents was investigated as well, as a potential method for their removal from waste water. For the determination of NGAL, a commercially available ELISA kit was used as the basis for method development. In the initial experiments the final product of the reaction of substrate with enzyme HRP (horse radish peroxidase) was transferred from microtiter plate into a microfluidic system, which served just for the sample transport to TLM detector on microchip. With comparable speed analysis we achieved LOD of 1.4 pg/mL which is 7 times lower in comparison to commercial ELISA test (LOD=10 pg/mL). For further development of the method for detection of NGAL with µFIA-TLM magnetic nanobeads were used as a solid support for primary antibodies of ELISA assay. By applying appropriate magnetic field the antibodies were kept in microfluidic system, which also enabled binding of NGAL, secondary antibodies and reaction of substrate with HRP. Developed method for NGAL detection with LOD of 2.3 pg/mL compares favorably with LOD for commercial ELISA tests (10 pg/mL) in standard microtiter plates and significantly reduces the analysis time. TLM in combination with microchip for NGAL detection reduces the duration of individual incubation steps (from one hour to 5 minutes) and at the same time shortens total analysis time from four hours for commercial ELISA test to 35 minutes allowing higher sample throughput. Analysis of real blood samples was also performed and it has shown good agreement between NGAL concentrations measured by magnetic nanobeads based µFIA-TLM with the concentrations measured by a commercial ELISA test. Such short analysis time of analysis and possible further optimizations are opening new possibilities for application of µFIA-TLM in medical diagnostics and clinical research. By using appropriate antibodies the method for developed NGAL detection could be easily adopted for detection of different pharmaceuticals or pollutants in environmental samples. We have also developed a magnetic nanobeads based ELISA assay for detection of anti-HPV-16 L1 antibodies in the sera of HPV-16 infected women. To ensure the selectivity, HPV-16 pseudovirions were used as an antigen for anti-HPV-16 L1 antibodies, which were detected with secondary HRP labeled antibodies. Initially the ELISA assay for antibodies against HPV pseudovirions was performed on a microtiter plate and an LOD of 3.8 ng/mL was achieved by measurement on a microtiter plate reader. When performing a µFIA-TLM measurement of the final ELISA solution the LOD was reduced to 0.9 ng/mL. Similar to the method for NGAL detection based on magnetic nanobeads, these were used as solid support for HPV pseudovirions and after carrying out all the incubation steps of the ELISA test in microfluidic chip the final product of the reaction of substrate with HRP was detected on TLM. With magnetic nanobeads based ELISA assay with µFIA-TLM for measurement of antibodies against PsVs of HPV-16 virus an LOD of 0.6 ng/mL was achieved, which is six times lower in comparison to classic ELISA on microtiter plate. Furthermore, the analysis time was reduced from ten hours to 30 minutes. The novel method was successfully validated by analysis of real sera samples from women who were previously diagnosed for infection with HPV-16 virus. For determination of iodinated MRI contrast agents we developed a new method based on the measurement of concentration of released iodide which allows indirectly semi-quantitative detection of concentration of iodinated contrast agents. For iodide release from parent molecule of contrast agent we applied a chemical reaction with Cu2+ ions in the presence of H2O2. Released iodide was first oxidized into iodine and then extracted into chloroform. Contrast agents degradation reaction showed 70 % of efficiency for removal of iomeprol, taking into account the 60 % overall efficiency of iodide oxidation and extraction. The extract was injected into microfluidic chip and iodine concentration was determined with TLM. Chloroform as organic solvent with low thermal conductivity and high temperature coefficient of refractive index is a good choice for TLM measurement due to high TLS enhancement factor, which theoretically provides 40 times higher sensitivity of TLM measurements as compared to water and a four time improvement in sensitivity for each milliwatts of excitation power, when compared to spectrophotometry. The developed µFIA-TLM method for indirect determination of contrast agents based on detection of iodine provides around 60 times lower LOD, with low reagent and sample consumption in comparison to spectrophotometry. The LOD of 18 ng/mL for iomeprol achieved with TLM is 16 times lower in comparison to LOD of 294 ng/mL for iomeprol determination with HPLC. In comparison to LOD of 133 ng/mL for iomeprol achieved with detection of released iodide by ion chromatography, µFIA-TLM enables around 7 times lower LOD. HPLC and HPLC/MS analysis showed that the parent compounds is completely removed after 120 min. of chemical degradation and that different degradation products are formed by cleavage of one or two iodine atoms. By this we have shown that the applied chemical degradation is efficient for removal of iomeprol and could be applied for treatment of waste waters after further optimization and reduction of reaction time. New analytical methods developed within this work provide limits of detection for the selected compounds which are significantly lower (up to 60 times) in comparison to conventional analytical techniques based on transmission mode measurements. At the same time the new methods allows shorter time of analysis and higher sample throughput for the purpose of fast screening methods. Magnetic nanobeads based µFIA-TLM ELISA assays developed within this work offer several advantages in comparison to commercial ELISA tests on microtiter plates such as: higher surface for antibody binding, lower reagent consumption, and shorter analysis time. Although the TLS technique didn’t reach appropriate stage of development and applicability for routine chemical analysis, improved methods for detection of NGAL and antibodies against HPV viruses could be applied for clinical studies and development of commercial tests for detection of viruses or other bioactive substances, which are needed for diagnostic purposes in hospitals.
Ključne besede: ELISA, NGAL, PsVs, kontrastna sredstva, TLM
Objavljeno v RUNG: 02.02.2017; Ogledov: 7046; Prenosov: 279
.pdf Celotno besedilo (4,66 MB)

8.
9.
Iskanje izvedeno v 0.04 sek.
Na vrh