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Vliv kyseliny askorbové na senzorické a analytické parametry bílých vín
Smrčka, Jakub
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.
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Studium hnědnutí dužniny a moštů z jablek
Chrastil, Jan
In this thesis with the title The study of browning of apple pulp and apple juice was, based on scientific literature, described the process and causes of colour change during processing of fruits. Colour change (browning) during processing of selected sort of apples was observed. In apple pulp was assessed the impact of chemical treatment (1% solution of ascorbic acid, 1% solution of potassium disulphite) on browning of apple pulp. In apple juice was observed the colour change and reduction of antioxidant capacity in time. The results were processed statistically and assessed in the discusion.
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Electrochemical sensor for ascorbic acid detection
Hlavička, Michal ; Kynclová, Hana (referee) ; Majzlíková, Petra (advisor)
This work deals with electrochemical detection of ascorbic acid using screen-printed three-electrode sensors. The work is divided into three parts, where the first describes the theory of thick-film technology, including the types and compositions of the pastes, fabrication and firing. The second part deals with the methods, measurement principles and the electrochemical detection of ascorbic acid. Experiments were done using screen-printed carbon electrodes in a solution of phosphate buffer and ascorbic acid. In conclusion the results are evaluated.
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Comparison of the fruits of some honeysuckle varieties in terms of content selected biologically active compounds
Veselý, Ondřej ; Diviš, Pavel (referee) ; Vespalcová, Milena (advisor)
This thesis is focused to the analysis of selected varieties of honeysuckle kamtschatica (Lonicera caerula var kamtschatica) and their comparison in terms of the content of biologically active substances. There were analysed only varieties grown in 2014. Theoretical part elaborates and characterized various parameters of biologically active compounds such as phenolic, anthocyanins and ascorbic acid and possibilities of their determination. Further it briefly surveys Kamchatka honeysuckle, its taxonomic and morphological properties and its nutritional properties. The experimental part of the work was focused on the description of the methods used for the analysis of biologically active substances and their analysis. Polyphenolic compounds and anthocyanin’s were determined spectrophotometrically and vitamin C was determined by high-performance liquid chromatography. The results and varieties were compared with each other. Overall, we can say that the variety with the highest content of all three analysed biologically active substances is a variety Valchová, which had the second highest content of polyphenolic compounds (546.3 mg · 100 g-1 fruits), the third highest contend of ascorbic acid (35.1 mg · 100 g-1 fruits) and the sixth highest content of anthocyanin (170.8 mg · 100 g-1 fruits)
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Vitamin C
Juráňová, Jana ; Hrstka, Miroslav (referee) ; Vespalcová, Milena (advisor)
The theme of this diploma thesis is an assessment of given nutritional parameters in selected kinds of lesser known fruits, specifically 10 varieties of sea buckthorn (Hippophae rhamnoides L.), 12 varieties of cornelian cherry (Cornus mas L.) and 6 varieties of blue honeysuckle (Lonicera caerulea var. kamtschatica). Harvests of two consecutive years (2011 and 2012) were analyzed in the case of blue honeysuckle. The theoretical part was focused on historical, morphological, taxonomic and nutritional aspects of individual plants and food or pharmaceutical utilization. The considerable part of the thesis is devoted to the characterization and the possibilities of determining the contained substances, namely ascorbic acid and polyphenolic compounds, especially anthocyanins. The content of the experimental part was a description of the methods and the results of the analysis of total solids, titratable acidity, total phenolics, total anthocyanins and ascorbic acid in fruits of the selected varieties of the above mentioned fruit species. Based on the measured results, the different varieties of fruits were compared to each other and evaluated.
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Changes in selected local fruits during freezing.
Matějková, Markéta ; Melounová, Jitka (referee) ; Márová, Ivana (advisor)
This diploma thesis was focused on study of low-molecular antioxidants present in various kinds of fruits, namely berries. In theoretical part detailed characterization of antioxidants studied in presented work and their biological effects are introduced. Further, principals of processing and storage of specified species of fruits are discussed. Changes observed during storage of specific fruits are described too. In practical part changes in content of selected antioxidants in berries were followed. As studied material strawberries, raspberries, blueberries, red and black currants were used. All kind of these fruits was stored in fridge for six months using several different kind of processing. Berries were stored as whole fruits, whole osmotically processed fruits by sucrose, raw pulp and sweetened pulp. At first, starting values of selected antioxidant parameters were measured in fresh fruits (ascorbate, total antioxidant activity, total phenolics, catechins and individual flavonoids). After freezing the same parameters were measured regularly in two month periods. As the most suitable method of fruit processing, with regard to antioxidant content, storage of the whole fruits or pulp can be recommended. Content of ascorbate decreased in all forms and species of the processed fruits during all the time of storage. Oppositely, the content of other studied antioxidants exhibited fluctuations or increasing trend. Sensory analysis was proved for the whole fruits and also for whole sweetened fruits.
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The influence of tomato ketchupes production technology on retention of nutritionally significance ingredients
Smolka, Bronislav ; Voldřich, Michal (referee) ; Ing.Helena Čížková, Ph.D. (advisor)
The work was focused on the verification of influence of quality of raw material and time-temperature conditions on the retention of nutritionally and sensory important components of the ketchups and other tomato based products. The goal of the theoretical part of this diploma thesis was the optimization of procedure of Czech tomato cultivar selection according to the highest refraction and intensive red colour. The influence of tomato ketchups production technology on retention of nutritionally significant ingredients was observed within the practical part. The samples of ketchups were sampled during different steps of production within one batch in company OTMA Sloko Mařatice. It was ketchup which was preserved by pasteurization in the glass bottle and ketchup which was preserved by hot filing to the plastic bottles. The content of lycopene, ascorbic acid, colour, viscosity, refraction and pH were measured in those samples. Furosine had been chosen as marker of thermal stress on material. The technologies can be compared on the basic of measured values from the view of retention or changes of nutritionally and sensory important components.
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Spectrophotometric determination of ascorbic acid in coloured samples
Moravcová, Gabriela ; Vespalcová, Milena (referee) ; Hrstka, Miroslav (advisor)
This bachelor’s thesis deals with spectrophotometric determination of ascorbic acid after the xylen extraction in coloured samples. The theoretical part deals with reactions, biochemistry and occurrence of ascorbic acid in foodstuffs. Also, it is dealt with various methods of determination of ascorbic acid, such as HPLC methods, electrochemical methods, titrimetric determinations, spectrophotometric determinations or polarographic method. In the experimental part of this method were first determined the concentration of ascorbic acid in the standards, then in real samples (vitamin tablets, orange juice and the juice of cultivated varieties of elderberry). Some validation parameters of the method were also determined. Sensitivity of the method was determined to 1,6772, linearity to 0,9990, limit of detection was set at 0,0466 mg/ml and the detection limit at 0,1552 mg/ml. Accuracy of the method was expressed as relative standard deviation, which gained 3,00% in value.
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Changes of antioxidants in selected fruits during long-term freezing
Štindlová, Jitka ; Lichnová, Andrea (referee) ; Márová, Ivana (advisor)
In this bachelor thesis some low molecular weight antioxidants contained in strawberries, raspberries, blueberries and cranberries are described. In the theoretical part also general characteristics of these fruits are introduced. Experimental part was focused on analysis of the changes of selected antioxidant content in the fruits. These changes were monitored during storage in two different conditions – in refrigerator and in freezer. In refrigerator whole fruits were stored for 8 days. The experiment in the freezer was performed for 2 months and the fruits were stored in four different processed forms – as a whole fruit, whole fruit impregnated by sucrose solution, as a pulp and pulp mixed with sucrose. Antioxidant content in fruits was analyzed by HPLC and spectrophotometry. The highest total content of antioxidants was found in strawberries, while the lowest values were found in raspberries. During storage some part of original antioxidant content stayed conserved, the highest content was preserved in blueberries processed as a whole fruits and impregnated whole fruits.
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