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Study of beer photodegradation by optical methods
Tayari, Tomáš ; Gabriel, Petr (advisor) ; Lustig, František (referee)
If beer is exposed to light radiation, it very quickly creates an undesirable unpleasant so- called lightstruck flavor. According to current ideas, 3-methyl-2-butene-1-thiol (MBT) is responsible for the lightstruck flavour in beer. The formation of MBT is associated with non- enzymatic reactions in which isohumulones and sulfuric components of amino acids and their derivatives emerge. Riboflavin (vitamin B2), which absorbs light and reacts with isohumulones in the excited state, acts as a photocatalyst. Light degrades riboflavin into its photoproducts. The aim of this work was to verify the possibilities of optical detection of beer photodegradation. An apparatus for detecting spectrally differentiated fluorescence intensity with a replaceable excitation LED source was constructed. The apparatus allows the excitation emission matrix of fluorescence (EEM) to be measured with selected excitation wavelengths. The fluorescence signal is scanned by a spectrophotometer with 90 ř offset to the excitation beam and corrected by its intensity which was detected in a straight line. The light source and detectors are connected to the measuring chamber via optical fibers. The fluorescence spectra of riboflavin, its photoproduct lumichrome and samples of fresh and defined light-damaged beer were measured on the...
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Study of thermal and photodegradation of beer and other fermented beverages
Škoda, Jakub ; Gabriel, Petr (advisor)
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.
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Study of the effect of immunological sdjuvants on experimental treatment of HPV-induced tumors by recombinant VACV and DNA vaccines
Gabriel, Pavel ; Němečková, Šárka (advisor) ; Mělková, Zora (referee) ; Reiniš, Milan (referee)
1 ABSTRACT The success of cancer vaccines depends on factors associated with the vaccine, which define the main parameters of effective immune responses such as its size and quality, as well as on factors related with the host, represented by the immunosuppressive mechanisms that allow the tumor to escape recognition by the immune system or negatively influence the function of effector T-cells. Attenuated, non-replicating viruses are at present preferred as VACV for safety reasons. A problem may arise concerning their lack of immunogenicity. Through the deletions of non-essential genes, vaccination vectors are therefore developed based on attenuated rVACV capable of replication, which induce a strong immune response. Genes of various immunological adjuvants (e.g., genes for cytokines and costimulatory molecules) are inserted into the vectors for the purpose of eliminating the influence of the immunosuppressive mechanisms of tumors. The first part of the work describes our study of the influence of vCCI on biological properties of rVACV derived from the Prague strain. Testing of vCCI deletion and insertion mutants expressing tumor associated protein HPV16 E7 has shown that secreted vCCI attenuated the virus in vivo, which correlated with reduced levels of the corresponding CC chemokines in the blood compared...
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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 QCM (Quartz Crystal Microbalance) for evaluation of beer properties
Škoda, Jakub ; Gabriel, Petr (advisor) ; Sladký, Petr (referee)
In this thesis the QCM (Quartz Crystal Microbalance) method was used to study beer properties. After necessary adjustments on the measuring apparatus the dependence of the output data on the temperature of used sample was measured. The measuring apparatus was connected to computer with direct graphical output to the display. Model samples of alcohol, glucose, wort and glycerol with various concentrations were measured as well as few beer samples. The object of the work is to find out whether QCM method is applicable for determining the alcohol content and original gravity of beer and studying beer stability.
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Electrochemical detection of purine bases using thick film Cu2O electrodes
Gabriel, Petr ; Prášek, Jan (referee) ; Pekárková, Jana (advisor)
This work deals with the production process thick films electrodes. It is focused on the Cu2O working electrodes preparation by screen printing and spray coating - methods on the corundum substrate. In this work are described both methods of fabrication and basic electrochemical methods. Prepared Cu2O electrodes were used for electrochemical detection of purine bases (adenine, guanine) using cyclic voltammetry. The effect of pH on the detection of purines was also examines.
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