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Study of thermal and photodegradation of beer and other fermented beverages
Škoda, Jakub ; Gabriel, Petr (advisor) ; Sigler, Karel (referee)
In this thesis the optical changes of beers and model beer solutions during their photodegradation were studied. The optical changes - change of absorbance - were measured on the prototype of apparatus COLORTURB and were correlated with sensory tested intensity of the lightstruck flavour of beer and with riboflavin content in samples. High correlation between the lightstruck flavour intensity, the loss of absorbance at the wavelength of 450 nm and the riboflavin content loss was found. The partial recovery of the absorbance for both beers and model beer solutions was found and was attributed to the riboflavin photoproducts transformation. Powered by TCPDF (www.tcpdf.org)
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Application of Separation Techniques Connected with Mass Spectrometry for the Analysis of Environmentally Important Compounds
Mácová, Daniela ; Čelechovská, Olga (referee) ; Márová, Ivana (referee) ; Demnerová, Kateřina (referee) ; Čáslavský, Josef (advisor)
The identification of the hydrolysis and photodegradation products of flexible polyurethane foams (PUFs) with addition of biooriginated and biodegradable additive was the first topic of this dissertation work. Separation of polyurethane foam hydrolysis degradation products, designed for ecotoxicological tests, was managed by high-performance liquid chromatography coupled with mass spectrometry (HPLC/MS). The degradations product structure was elucidated by tandem mass spectrometry (MSn). PUF photodegradation products were obtained by exposure of materials by irradiation at 254 nm. Semi-volatile degradation products were isolated from the exposed polyurethane by n-hexane extraction; volatile compounds were collected by solid phase microextraction (SPME). Gas chromatography with mass spectrometry (GC/MS) and complete orthogonal tandem gas chromatography with mass spectrometry (GCxGC/TOF MS) was used for separation and identification of photodegradation products. The influence of the bio-filler on the character of degradation products and the possible effect of PUF degradation products on the environment was discussed at the end of this section. The determination of isoprostanes – markers of oxidative stress in tissues of beadlet anemone (Actinia equina) was the subject of the second topic. F2-isoprostanes were synthesized from the arachidonic acid. With thereby prepared isoprostanes the method of determination by liquid chromatography with tandem mass spectrometry (HPLC/MS/MS) was developed and optimized. The isoprostane isolation process from the Actinia equina tissues was optimized with solid phase extraction (SPE). The resulting methodology was used to quantify isoprostanes in tissues of anemones, which were exposed to both moderate and high temperature changes. The temperature changes were used to initiate the oxidative stress in organisms. In addition, concentration levels of unknown compounds were also monitored. These unknown compounds were extracted from tissues together with F2-isoprostanes and their identity is discussed in this dissertation work too. The possibility of using isoprostane levels in the Anthozoa tissues for the oxidative stress monitoring is discussed in the conclusion of this work.
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Photodegradation of monuron in the presence of goethite and carboxylic acids
Bajt, O. ; Krýsa, J. ; Jirkovský, Jaromír ; Zita, J. ; Paušová, Š.
Iron is one of the most abundant elements in the environment. It is also an essential micronutrient for most known aquatic organisms, Its role in primary production in natural waters is very important. However, the low solubility of iron oxides at pHs, significant the low availability of iron to aquatic plants and microorganisms. Goethite, an iron oxohydroxide, is one of the most abundant iron oxide in the natural marine environment.
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