National Repository of Grey Literature 58 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Extraction and application of keratin from sheep wool
Jahnová, Kateřina ; Veselá, Mária (referee) ; Kovalčík, Adriána (advisor)
This thesis deals with the isolation of sheep wool keratin for using this protein in composite films. The goal was to compare the yield of alkaline hydrolysis of sheep wool using different concentrations of sodium hydroxide. It was found that the most effective was alkaline hydrolysis using 2wt% sodium hydroxide showing 80 % effectiveness of keratin isolation. Fourier infrared spectroscopy, differential scanning calorimetry a thermo gravimetric analyses confirmed that the isolated materiál from sheep wool was keratin. The isolated keratin was used as filler for the preparation of polyvinyl alcohol-based composite films. The mechanical properties of keratin/polyvinyl alcohol films showed that keratin played the role as an active filler for polyvinyl alcohol composites.
Antibacterial activity of photoactive surfaces
Rabenseifnerová, Barbora ; Králová, Marcela (referee) ; Veselá, Mária (advisor)
This master's thesis deals with the antibacterial activity of photoactive surfaces in flia with a known content of zinc pyrithione in combination with the photoactive part. Individual flia were exposed to illumination for a given period of time to confirm photoactive ability and stored for comparison in the dark for the same time. The imprinting method was used and supplemented by a method based on ISO standard 27447:2019.
Natural dyes for smart packaging
Nyklesová, Ludmila ; Dzik, Petr (referee) ; Veselá, Mária (advisor)
This thesis focuses on the use of natural dyes in smart food packaging as pH change indicators. The theoretical part of the thesis describes smart packaging, which can be divided into active and intelligent packaging. Within intelligent packaging, the thesis focuses mainly on pH indicators, including their composition, i.e., the polymer used and the dyes, with an emphasis on anthocyanin dyes. The theoretical part also includes a description of the methods used to measure the color changes of prepared indicators. In the experimental part of the thesis, anthocyanin dye is extracted from Aronia melanocarpa berries and thin films containing the anthocyanin extract are prepared. The color change of the prepared thin layers is further studied in an environment with a low concentration of ammonia. Layers that showed a reaction to the ammonia environment were subsequently overprinted with white UV varnish, and their reaction to an environment with low ammonia content was observed.
Preparation of hydrogels with the addition of grape pomace extract
Mojžíšek, Jan ; Veselá, Mária (referee) ; Kovalčík, Adriána (advisor)
The scope of this bachelor thesis is the preparation of hydrogels with antioxidant properties. These properties are achieved by the addition of grape pomace extract. The theoretical part of the thesis briefly summarizes the basic characteristics of the gels and describes the basic quantities in rheology. Furthermore, the classification, preparation and use of hydrogels are described. Attention is paid in particular to gels falling into the category of edible hydrogels. Information on antioxidants and matolins is also given. In the experimental part, extracts from grape pomace are characterized in terms of carbohydrate content, phenolic compounds and antioxidant properties. The extraction itself was carried out in different concentrated aqueous ethanol solutions. The extract with the highest total antioxidant activity, as determined by the ABTS method, was used for the preparation of the hydrogels. Agarose is used for the preparation of hydrogels. The change in the rheological properties of the hydrogels due to the addition of the prepared extracts was observed. The specific structures in the hydrogels were determined by FTIR.
Printed indicator of pH value designed for food packaging
Valíková, Michaela ; Kovalčík, Adriána (referee) ; Veselá, Mária (advisor)
The aim of this diploma thesis was to design an intelligent indicator of pH value for food packaging. Intelligent packaging is a new group of packaging that is able to provide costumers real-time information on the quality of packaged food through various indicators. In the theoretical part, a search was made on the topic of intelligent packaging with emphasis on freshness indicators. A smaller part was devoted to the issue of food spoilage. Emphasis was also placed on the description of the main components of the functional layer, and on the issue of chitosan crosslinking. In the experimental part, the crosslinking of chitosan with the addition of polyvinylalcohol using vanilin was studied. Prepared layers were monitored for their solubility and degree of crosslinking, which was determined using the ninhydrin method. To create a colorimetric pH indicator, an anthocyanin extract obtained by extraction from red cabbage was incorporated into the composition. A total of 3 anthocyanin extracts were prepared, for which the total anthocyanin concentration was determined by the difference method. The color of the prepared layers was evaluated spectrophotometrically under the action of various concentrations of the ammonia gas. The stability of the layers over time was also monitored. The last part of the experiment was the application of the prepared layers in a package with real meat.
Disposable sensor of ammonium for intelligent packaging
Nentvichová, Aneta ; Kořínková, Radka (referee) ; Veselá, Mária (advisor)
This diploma thesis is focused on the problematic of the smart packaging and deals with the preparation of disposable ammonia sensors/indicators and the subsequent color measurement of prepared sensors/indicators using the CIE L* a* b* color space. The theoretical part of the diploma thesis focuses on active and intelligent packaging, using ammonia sensors/indicators. The emphasis is placed on the main components of the sensor/indicator, i.e., chitosan as a polymer and curcumin as a dye. The theoretical part also includes the problematic of meat degradation, which plays a very important role in this thesis. The experimental part was divided into two parts. The first part was to prepare layers that will respond in different colors based on the concentrations of ammonia. Prepared layers were sensitive to ammonia across all concentrations, and based on this result, ascorbic acid was applied to compositions to achieve a calibration retention of the selected amount of ammonia. The second minor part of the experiment was the application of selected layers to packages with real meat.
Preparation and characterization of Echinacea extracts
Pallová, Jana ; Veselá, Mária (referee) ; Vítová, Eva (advisor)
Echinacea purpurea is a rich source of biologically active compounds, which are attributed to several therapeutic effects. This thesis is focused on the optimization of the extraction process, considered these substances. Maceration was chosen as a type of extraction, due to its simplicity. The Optimal conditions were solid-solvent ratio 1: 5, 40% ethanol, 60 °C, 60 minutes. An extract from the dried flowers of Echinacea purpurea was prepared by this optimized process. The content of total phenolic compounds was set on 365.18 ± 3.51 [mg_GAEl^(-1)] and the antioxidant activity was 507.50 ± 6.89 [mg_TEACl^(-1)]. The percentage of radical scavenging activity ABTS•+ was 95.45 ± 1.30. The antimicrobial activity of the extract was tested against 3 microorganisms – Escherichia coli, Bacillus cereus and Candida glabrata. There was not detected inhibitory effect on the growth of microorganisms. In a total, 39 volatile compounds were identified, and the biggest group were represented sesquiterpenes (70.9%). The obtained results confirm that Echinacea extract has antioxidant activity and contains several interesting aromatic substances, In the future, it can be used as a natural resource of nutritionally and sensory valuable compounds, e.g., into various foods and delicacies.
Sensor of food packaging environment quality
Dobiáš, Vojtěch ; Syrový, Tomáš (referee) ; Veselá, Mária (advisor)
The aim of this study was to prepare thin polymer layers able to give a color change response to oxygen. Thin layers were prepared with different polymers and dyes. The rate of photocatalytic reduction of a dye and the rate of the color change response to oxygen were studied. To verify oxygen sensitivity of a prepared layer, oxygen absorbers were used to create anaerobic conditions. The effect of visible light irradiation on a prepared layer was examined as well. Influence of glycerol content on the kinetics of the photocatalytic reduction and the color change response was studied. Considering both reactions, the glycerol content of 1 % was found to be the most suitable. Methylene blue in prepared layer was reduced 48 s after previous UVA irradiation with intensity of 0,1 mWcm-2. The color change response to oxygen is readily distinguished by the naked eye within 20 minutes.
Microbial contamination packaging glass
Bělohoubková, Tereza ; Vítová, Eva (referee) ; Veselá, Mária (advisor)
The bachelor thesis contemplates the formation of microbial contamination during production of glass packaging used in food industry. The theoretical part defines the word packaging, its function and legislation of glass packaging. Glass packaging production is described as well as arising risks of potential microbial contamination. Unacceptable microorganisms with ability to live on the surface of glass packaging and possible determination of the microorganisms are characterized in the thesis. In the practical part swabs of produced glass packaging were analyzed by ATP bioluminescence and pH of the inner glass surface was determined to assess species of microorganisms able to live on glass surface. Conclusion of the thesis discusses establishments to lower the risk of microbial contamination.
Disposable pH sensor
Dvořáčková, Sabina ; Kovalčík, Adriána (referee) ; Veselá, Mária (advisor)
This bachelor thesis deals with thin polymer layers containing substances capable of reacting to changes in the pH. In theory are processed informations of smart packaging including legislation of general food packaging. Natural substances forming the basis for the production of edible films are also described. An indicator of ammonia in composition of PVA and red cabbage anthocyanins was studied here. The prepared layers were tested for gaseous NH3. Layers containing anthocyanins responded with a very intense color transition from purple and blue to turquoise.

National Repository of Grey Literature : 58 records found   1 - 10nextend  jump to record:
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