The main objective of the Thesis is to understand the oxidation of must, especially enzymatic oxidation. It is caused by the oxidative enzymes that are already present on the grapes in vineyard, especially on those badly infected by mushroom diseases. The two main oxidative enzymes that need to be targeted are tyrosinase and laccase, collectively called polyphenoloxidasi (PPO). These most active oxidative enzymes, which already oxidize the must in the beginning of wine production and degrade the quality of future wine, belong to the group of oxidoreductases where oxygen is a catalyst for enzymatic activity and the phenolic compounds are substrates. Another main goal of the Thesis is to determine polyphenol oxidase activity on several samples of varieties and to compare how it affects other wine parameters such as acids, sugar content, etc. We will discus the oxidation of caftaric acid and its subsequent conversion to quinones. Quinones are just the product of the oxidation of phenolic compounds due to the activity of these enzymes. Caftaric and coutaric acids are the most oxidizable compounds for these enzymes and will therefore be discussed in more detail. It is also necessary to focus on possible protection against enzymatic oxidation.

Fish muscle contains omega-3 fatty acids and high quality protein and other valuable nutrients. On the other hand, due to the high content of water, neutral pH, presence of PUFA and sensitive amino acids, fish muscle is a very perishable food. The progress of lipid and protein oxidation as well as interaction between the oxidation products could have a negative role during storage time. Negative effect of oxidation on the fish fillet quality has been reported by several authors, but still the pathways and products of protein oxidation owning to the diversity of the protein oxidation products is not clear. Pathways of lipid and protein interaction, target amino acids, storage conditions and also, final impact on the fish muscle quality have been investigated in this study. We examined the quality of fish muscle in common carp and perch during different storage conditions (+4°C and -20°C). Also, we compared some quality parameters in perch muscle from two different rearing systems to identify the pathways and products of oxidation. The present study investigated the oxidation progress with respect to TBARS and carbonyls as markers of lipid and protein oxidation respectively as well as contribution of PUFA on the lipid oxidation development. Further, the effect of storage conditions and oxidation on the textural and sensorial parameters were examined. Possible changes of pH, rigor index and biogenic amines, during post mortem were studied. Additionally, we performed proteomic analysis in order to investigate more deeply the protein alteration and find a correlation between protein structures and fish muscle quality. Our results showed a good stability in common carp (Cyprinus carpio) fillet during 6 months storage at -20oC. According to our results, we observed a significant decrease in the firmness of common carp muscle after 1 week and then it was constant while liquid loss increased significantly with storage time. Regarding the sensory parameters, we could not find any differences in the examined parameters in both stored raw and cooked fillets compared to the fresh one. Although, both lipid oxidation parameters (TBARS and PV) were increased significantly but it did not reach the critical level for human consumption. On the other hand, protein oxidation which is involved in WHC deterioration was increased significantly. In addition, we investigated the muscle quality of Eurasian perch (Perca fluviatilis L.) from two rearing systems (RAS and pond). During frozen and refrigerated storage, we observed a significant increase in the amount of TBARS and carbonyls in both rearing systems. Comparison between both rearing systems did not show any differences in the amount of TBARS while carbonyl was significantly higher in the RAS fillets rather than pond fillets particularly, until 4 month storage at -20oC. Also, we found a significant increase in liquid loss and considerable decrease in firmness in the fillets from both rearing systems. Our results showed higher firmness and liquid loss in the RAS fillets compared to the pond one. Proteomic analysis on the fillets from both rearing systems during frozen storage showed more stability in the RAS fillet however, western blot revealed more oxidized carbonyls in the RAS fillets rather than pond fillet specially, at time 0 and 4. Probably, formation of ice crystals and accumulation of ROS have key roles on the development of oxidation during frozen storage while enzymatic activity follow by protein degradation are important during refrigerated storage.

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This diploma thesis dealt with the influence of the degree of must oxidation on the sensory and analytical properties of wine grape. In the literary part of the thesis, chapters dealing with must, phenolic compounds, oxygen, the process of oxidation in must and wine, their effects on sensory properties and various technological methods of oxygen supply during wine production were processed. Two varieties of grapevine were used for the experiment. The aromatic category was represented by the Cvetočnij variety and the non-aromatic Grüner Veltliner variety. The musts of the two varieties were divided according to the degree of oxidation into a reductive and oxidative variant, and also according to the length of maceration to 0 and 24 hours. Oxidative variants were already hyperoxidised in the must after pressing and reductive variants were added sulfur dioxide. After pressing, all the samples were left for 24 hours by gravity sedimentation followed by spinning from the sludge and fermentation. After alcohol fermentation, the samples were coiled from coarse yeast and mixed for 4 months on fine yeast at regular intervals of 1 per week. Basic parameters, dissolved oxygen content, total polyphenols, flavanols, sulfur dioxide, optical density and color intensity were analyzed in various technological stages of production (after pressing, after sludge, on the 5th day after fermentation, after the first twisting, after 4 months). All wine samples were sensory evaluated after 4 months of maturation. The results of analytical and sensory analyzes were processed, statistically evaluated and shown in well-arranged graphs and tables. From the acquired knowledge was concluded for the purpose of its use in possible practice.

The diploma thesis deals with methods of assessing the quality of selected vegetable oils exposed to different thermal and light conditions for a set period of time. In the practical part, the quality and stability of oils is evaluated by the colour of the oils using the spectrophotometry method, content of fatty acids by the acid value and the determination of the fatty acids is assessed by the gas chromatography method. The results show that the stability of vegetable oils is most affected by exposure to the light at the temperature of 22°C in a translucent packaging. The results of spectrophotometric colour measurements revealed changes in L*, a* b*, C* and h* over a period of time, and the values varied when exposed to different storage conditions as well. The acid value has changed significantly over the course of storage in all the oils. The content of fatty acid varied during storing but was not affected by different storage conditions.

Title: High pressure CO and methanol oxidation study over nanopowder Rare Earth Oxides and platinum thin film catalysts Author: Mgr. Andrii Rednyk Department: Department of Surface and Plasma Science Supervisor: Prof. RNDr. Vladimír Matolín, DrSc. matolin@mbox.troja.mff.cuni.cz Abstract: This doctoral thesis focuses on reactivity study of nanopowder rare earth oxides (REOs) and platinum based thin film catalysts using microreactor with high pressure reaction cell. REOs nanoparticles were prepared by new approach based on sol-gel chemistry. Magnetron sputtering technique was used for preparation of thin film samples. In the first part of the thesis CO oxidation on REOs and on Pt, PtOx thin films were performed. Among prepared REOs catalyst better activity exhibited alumina stabilized ceria, due to higher surface area. Both Pt and PtOx deposited on silicon substrate exhibited similar activity. When carbon (G-foil or C interlayer) is used as support, activity of Pt thin film decreases while PtOx preserves high activity. In the second part of the thesis steam reforming of methanol (SRM) and partial oxidation of methanol (POM) were performed on Pt thin films. It was shown that PtOx thin film exhibited superior activity compared to other samples with the same thickness. It is due to the reduction of platinum...

This thesis was focused on the effect of ascorbic acid on sensory and analytical parameters of white wine during production technology. The theoretical part is devoted to a detailed description of the mechanisms of oxidation of ascorbic acid and ultimate degradation products of ascorbic acid. In the theoretical part are also given basic methods for the determination of ascorbic acid. Another part focuses on the synergy of ascorbic acid and one of the most important substances in the manufacture of wine, sul-fur dioxide. The practical part includes an attempt was founded in 2014. The study compared different doses of ascorbic acid and sulfur dioxide have been added to the mash two varieties, Riesling and Grüner Veltliner. Attempt monitors antioxidant properties of ascorbic acid and its influence on the analytical and sensory component of the resulting wines. Based on the results, we can conclude that ascorbic acid has antioxidant capabilities asking if it was properly supplemented with sulfur dioxide.

This diploma theses addresses the changes in the composition of animal lipids during cooling storage and after processing. It was used mincing fish muscle of common carp (Caprinus caprio). After application of selected herbs has been studied their antioxidation effect on the stability of fish lipids after heat - treatment and coooling storage. In total, two analyses were performed. Each analysis consisted of measuring temperature every two to three days for 20 - 23 days. During this period, the effect of oregano (Origanum vulgare), summer savory (Satureja hortensis L.) and greek oregano (Origanum heracleoticum L.) to heat-treated meat in cooling storage was observed with the help of the TBA value as an indicator of the oxidation level . Fish meat contains a high percentage of water and PUFA (polyunsaturated fatty acids) resulting in a higher level of lipid autooxidation. By applying the herbs into the samples, it is possible to slow down the lipid autooxidation and prolong the storage period. The antioxidative effect of herbs was present in all measuremnts. There were no statictically significant differences between greek oregano and summer savory. Statistically significant effects appear between saummer savory and greek oregano and between oregano and greek oregano. During the whole period of measuring TBA, its values were low. No difference between the samples with the herbs and the standart sample was statistically proven. However, cold storage of fish meat with the help of antioxidative effect of the herbs can be considered as an effective reduction of oxidation in the meat.

Under suitable conditions anodic metal oxidation leads to growth of complex porous structures. The initiation and growth of these structures is an interesting and challenging task for electrochemical modelling. One must identify chemical reactions in a multi-phase framework, derive a proper partial differential equations and solve them in time dependent domains. In this work, electrochemical model for the oxide growth in nano scales is presented. Physically motivated equations are formulated with precise mathematical meaning and existence of solutions is studied. Electrostatic potential fulfilling high-field conduction law and interfacial jump conditions is sought for. Numerical discretization is performed with the use of finite element method and free boundaries are tracked with characteristic level-set functions. Basic mechanism governing the growth of porous structures is given and numerical experiments are explained on it's basis. This thesis presents novel contributions to the electrochemical and mathematical picture of nanopores growth.

This diploma thesis was focused on the possibilities of extending the shelf-life of fish products by dipping containing seven commercial additives. ANTIBAK, MIC STAB, Bakont, SEA-F75, Misocarine LR, SAFE A Plus and AMX liquid. The effectiveness of these substances on the extending of shelf-life was evaluated on the basis of tests of TVC (total viable count), level of fat and protein oxidation, determination of nutritional parameters of muscle, and finaly sensory analysis. Experimental species were 2 important commodities for the Czech aquaculture rainbow trout (Oncorhynchus mykiss) and common carp (Cyprinus carpio). The project was divided into 6 sub-stages. During testing was the initial number of aditives (7) limited by stepwise selection for 2 preparations. Namely Bakont and AMX liquid, which were tested further on trout (filet with skin and scales) and carp (filets with skin without scales) chilled bulk and chilled packaged under vakuum. For trout was studied antimicrobial effect of dipping on eviscerated fish with the head with- or without gills. Treated trout fillets in bulk and vakuum-packed showed significantly less abundance of muscle mikroflora. In the case of carp fillets chilled bulk we can not say that the bath had influence on the CMP in meat. However, the combination of dipping and vakuum packaging was singnificantly different between the control and product Bakont. AMX liquid was not applied in this case in sufficient dose or in sufficient time to carp muscle. A positive finding is that the application of the aditives to the product "eviscerated trout with head" it does not matter, whether the gills are left in fish or not. However, in all cases the analysis of the presence of pathogens Escherichia coli, Salmonella spp. or Listeria monocytogenes were negative. From the results of sensory analysis can be concluded, that the substances contained in aditives are not reflected in the sensory properties of tested fish.