National Repository of Grey Literature 113 records found  beginprevious103 - 112next  jump to record: Search took 0.00 seconds. 
Study of emulsion stability by means of physical-chemical and optical methods
Kuchyňová, Jitka ; Veselá, Mária (referee) ; Zmeškal, Oldřich (advisor)
The diploma thesis deals with the stability determination of model O/W (30/70) emulsions at 25°C. In fact, the time and emulsifier concentration (Tego Care PS) dependences of physical properties (aging) were monitored. In the second part of the work, the influence of conservant on emulsion stabilities were studied. In order to study physical properties of emusions rheometry, differential scanning calorimetry (DSC) and optical microscopy were employed. The rheological measurement provided information on viscosity and viscoelastic modulus. DSC experiments used the repeated freezing/thawing cycles which allowed monitoring of changes in crystallization temperature of water present in emulsions and melting enthalpy of ice formed during the cooling. The optical microscopy was used to examine the change in oil droplet size in the course of emulsion destabilization and phase separation. In this case the image analysis was carried out using program HarFA. The results showed that due to the emulsion creaming, the oil droplets diffuse and aggregate which causes phase separation. Those processes were quickest for the emulsion with lowest emulsifier concentration 0.1 % (destabilization during 51 days) The emulsions with emulsifier concentration about 1.5 and 1.3 % were stable at least for 4 months. The presence of the coemulsifiers increased the elastic modulus and descreased the phase difference due to the network formation. It was shown that for the stability determination is necessary to use conservant due to risk of microbial contamination. DSC experiments allowed to distingush samples prepared under different conditions. Lower rotational speed during emulsion preparation caused the appearance of two melting and crystalization peaks while for higher speed only one peak was observed.
Microbial contamination of photographic materials
Ouředníčková, Veronika ; Dzik, Petr (referee) ; Veselá, Mária (advisor)
This diploma work is focused on a study of microbial contamination of photographic materials. In the first part of this work the information about the archive and museum microbial contaminations were collected. The most frequent contaminants of photographic collections – Penicillium chrysogenum and Aspergillus niger were studied. Their activity on photographic papers Fomaspeed and Fomabrom was evaluated. It was found that at the given experimental conditions the image layers of Fomaspeed paper are resistant to fungi mycelium growth. On the other hand, the Fomabrom paper image layer was irrecoverably damaged by action of fungi mentioned above. The degree image layer deterioration was evaluated with the aid of sensitometric curves.
The effect of silver on yeasts photokilling process efficiency
Vrchovecká, Petra ; Pekárková, Jana (referee) ; Veselá, Mária (advisor)
In this diploma thesis, photocatalytic effect of titanium dioxide with addition of silver was described and demonstrated on inactivation of the yeast Candida vini. Titanium dioxide was prepared by sol-gel process and deposited by printing metod on soda-lime glasses. On the deposit of titanium dioxide was added silver in various concentrations which increased effect of TiO2. Inactivation of yeasts was examined by effectiveness of UV light with intensity 170 and 100 W/m2.
Production of biogenic amines in double moulded cheese
Šuláková, Miroslava ; Standara, Stanislav (referee) ; Veselá, Mária (advisor)
For production of double moulded chesses are used lactic acid bacteria, which can be present in a form of non-starter lactic acid bacteria or as starter or adjunct culture. Genera Lactobacillus spp. and Enterococcus spp. are prevalent microorganisms present in these cultures. Of course, these microorganisms are for us interesting because of their possibility of coagulation, proteolytic possibility, probiotic function and antibiotic resistance, but especially because of their decarboxylation abilities. Bacteria contain decarboxylation enzymes, which are able to decarboxylized free amino acid, which rising at proteolysis during process of manufacturing and cheese ripening. Biogenic amines are the result of proteolytic activity. Biogenic amines occur practically in all foodstuffs as a common product of metabolic processes. BA are mainly presented in fermented food (cheeses), where rice just microbial action. Typical representatives of biogenic amines, which occurs in double moulded cheeses (Sedlčanský Vltavín, Bresse bleu) and in blue cheeses (Bleu des Causses, Bleu d'Auvergne) are cadaverine, putrescine, tyramine a 2 fenylethylamine and in much smaller amount histamine, spermidine and spermine too. On assessment concentration of BA is used high pressure liquid chromatography with reverse phase (RP HPLC) with utilizing simple direct derivatization with dansyl chloride and detection by UV VIS detector.
Photocatalytic inactivation of yeast in flow reactor
Lipenská, Michaela ; Drbohlavová, Jana (referee) ; Veselá, Mária (advisor)
This diploma thesis focuses on the photocatalytic effect of titanium dioxide and ultraviolet light. Theoretical part shows the effect of titanium dioxide and aplication in various branches. Antibacterial effect of titanium dioxide iluminated by ultraviolet light was observed in the flow tube reactor on the yeast Hansenula anomala. After adjusting the optimal flow rate experimented with different inicial concentration of yeast cells. To increase desired effect also silver was used in the photocatalytic system. As observed in many previous studies, silver decreases the time needed for killing the microorganisms. The optained date were analysed.
Antimicrobial effect of plant extracts
Konderla, Patrik ; Vespalcová, Milena (referee) ; Veselá, Mária (advisor)
The purpose of this bachelor thesis was to research the possible antimicrobial activity of various extracts of rosehip tea and also determine the antioxidant activity and the concentration of biologically active compounds (polyphenols and flavonoids) in these tea. Teoretical part describes basic information about plant Rosa canina and chemical composition of rosehips, summary of the natural biologically active compounds and general classification of tea. The practical part is focused on detection of antimicrobial activity of tea extracts against bacterial strains Serratia marcescens and Bacillus subtilis as well as spectrophotometrical determination of concentration polyphenols, flavonoids and overall antioxidant activity of these extracts. From the results flow the testing aqueous extracts rosehips tea analysed antimicrobial effects. Also was found, that these extracts has high content of polyphenols and flavonoids.
Basic chemical characteristics of chokeberry juices
Zámorská, Vendula ; Veselá, Mária (referee) ; Vespalcová, Milena (advisor)
This bachelor thesis deals wirh characteristics of berries and assessment of basic chemical parameters of chokeberry juices (Aronia melanocarpa). The theoretical part is about the basic botanical description of selected varieties of Aronia and its taxonomic status. The following are important substances contained in fruits and their part in human nutrition and use for food purposes. The end of the theoretical part of bachelor thesis is about basic methods of determining the nutritional parameters of berries. In the experimental part solids content of the fruit. Furthermore soluble dry matter content, pH, titratable acidity, formol number, reducing sacharides and ascorbic acid by spectrofotometry were determined. Based on the results, juices were compared.
Photocatalytic inactivation of yeasts
Šupinová, Lenka ; Zita, Jiří (referee) ; Veselá, Mária (advisor)
This diploma thesis is focused on the study of the effect of ultraviolet radiation and titanium dioxide on the yeast Candida vini. Photocatalytic inactivation of this yeast was performed on various types of titanium dioxide films, which were immobilized on soda lime glasses. Acridine orange was used as a dye to distinguish live and dead yeast cells after certain irradiation time. Live and dead cells emit different light in colour after staining in acridine orange. Candida vini photocatalytic inactivation depends on the amount of titanium dioxide immobilized on glass as well as on the structure of its surface if the lamp intensity remains the same. Kinetics of this photocatalytic process was studied, too.
Study population of bacteria by image analysis methods
Ševčík, Jan ; Veselá, Mária (referee) ; Zmeškal, Oldřich (advisor)
This bachelor thesis is focused on monitoring and application of image analysis methods on Bacillus megaterium and Cupriavidus necator bacteria. The introduction describes a general knowledge about bacteria, microscopic and image analysis methods. At first it was necessary to prepare suitable microscopic specimens using Gram staining for the observation of a bacteria cell. Every picture of bacteria was taken using a CCD camera and a microscope. Box–Counting method was used to identify the optimal threshold value, corresponding to their fractal measure (or surface areas covered with bacteria) and fractal dimension (or entropy of their arrangement on the surface area). After thresholding, the images were further processed using the Mass–Radius method, which defines a distribution of bacteria relative to the centroid of a cluster.
Probiotic bacteria in pharmaceutical products
Suranová, Mária ; Vránová, Dana (referee) ; Veselá, Mária (advisor)
Probiotics are live microorganisms, that when administered in adequate amount confer a health benefit on the host. They are used as part of specific milk products and either as dietary supplements in form of tablets, capsules, coated pills and sirups. The most famous probiotic microorganisms are bacteria of Lactobacillus and Bifidobacterium genus, that belong in group of lactic acid bacteria. For the assessment of probiotic preparations is used broad range of methods for the microbial analysis of foods. These methods can be separated on quantitative, that enumerate amount of microorganisms in product and qualitative, that are capable detect presence or absence of certain microorganisms. Both types of the methods have large importance in control of the efficiency probiotic preparations.

National Repository of Grey Literature : 113 records found   beginprevious103 - 112next  jump to record:
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