|
|
Caffeine degradation by high frequency discharge in solutions
Korečková, Svatava ; Mravcová, Ludmila (referee) ; Kozáková, Zdenka (advisor)
The bachelor thesis deals with the degradation of caffeine in solutions by a high frequency discharge generated directly in the solution. The influence of experimental conditions such as the initial pH and conductivity of the solution, caffeine concentration or electrode geometry was studied. The prepared caffeine solutions had a concentration of 10–100 ppm and their initial pH was adjusted with electrolytes (NaCl, Na3PO4, Na2HPO4 and NaH2PO4). All experiments were performed in a batch plasma reactor consisting of a 400 ml beaker and two electrodes. UV-VIS spectrophotometry was used to determine the amount of degraded caffeine. It was found that the experimental conditions (electrical conductivity, power, type of electrode used, electrolyte used) have an effect on the degradation of caffeine. The most suitable electrolyte appears to be NaCl and the initial specific electrical conductivity set in the range of 400–500 S·cm–1.
|
|
|
Preparation and use of selected nanoparticles in cosmetics
Hoová, Julie ; Němcová, Andrea (referee) ; Márová, Ivana (advisor)
The Bachelor thesis is focused on preparation and use of selected nanoparticles in cosmetics. The theoretical part deals with general characterization and use of caffeine, phenolics and vitamin C in cosmetics. Further, characterization of liposomes and possibilities of encapsulation of active substances gained from natural sources were introduced. In experimental part liposomes with encapsulated active substances were prepared by three different techniques. Encapsulation efficiency was determined by HPLC/PDA, phenolics spectrophotometrically and vitamin C by titration. Prepared particles were monitored for size and stability by dynamic light scattering. Furthermore, long-term stability of liposomes in model conditions was evaluated as the amount of the active substances released during incubation. In this work was found out that from all tested samples co-encapsulated liposomes are probably the best application form which can be used in face lotion or gel. Co-encapsulated liposomes exhibited relatively high encapsulation efficiency, good stability and thanks to quality of active substances they meet customer’s requirements of cosmetic industry.
|
|
|
Energy drinks in contemporary nutrition
Krňávková, Martina ; Hrstka, Miroslav (referee) ; Vránová, Dana (advisor)
Bachelor's thesis is dealing with consumption of energy drinks and their effects on the human organism. The introductory part gives an overview of the most frequently occurring components of energy drinks including their chemical composition, properties and sources of these substances and nutrition recommendations. The next section describes the effects of consumption of energy drinks on the human body and health in general. The final part deals in detail with the impact of their consumption on sports performance and on human health and the possible consequences of consuming energy drinks combined with alcohol.
|
|
|
Influence of coffee making process on chemical composition of brewed coffee
Trenzová, Kristina ; Divišová, Radka (referee) ; Diviš, Pavel (advisor)
This bachelor thesis deals with the influence of baristic coffee preparations on the chemical composition of the obtained beverage. Teoretical part of this thesis focuses on coffee growing, processing technology and the chemical composition of coffee beans. In the experimental part were measured samples of espresso coffee, samples prepared by moca pot, flip-drip method, filtrated coffee, samples prepared by french-press technique, vacuum pot samples and boiled coffee. The samples were prepared according to the baristic techniques at first and later with adjusted water and amount of coffee so these methods could be compared with each other. This work focuses on the determination of caffeine and acrylamide content by liquid chromatography, validation of HPLC method, determination of total phenolic content by Folin-Ciocalteu reagent, determination of organic acids by ion chromatography, determination of selected macro and micro elements by inductively coupled plasma in optical emission spectrometry and analysis of aromatic substances using gas chromatography. Based on the processed results and compared methods, it was shown that the moca pot had the greatest influence on the content of caffeine, acrylamide, organic acids and total phenolic substances, and the flip-drip with vacuum pot method had the greatest influence on the content of aromatic substances. From a baristic point of view the highest concentration of caffeine was 3689 mg/l in coffee based on flip-drip method, and concentration of acrylamide was 25,4 mg/l in the coffee based on the same method. The highest value of total phenolic content was determined in moka pot to c = 5,23 g/l. Regarding the mineral representation, the mineral decomposition of coffee beans and espresso were compared, and the highest values were reached by potassium, namely the concentration was 577 mg/l per 1 g of mineralized sample, in the cup of espresso the potassium concentration was 2461 mg/l. The highest content of organic acids was determined in the beverage prepared by moca pot, in terms of selected acids, the largest representation had the succinic acid with the concentration 599,8 mg/l. The highest content of aromatic substances was found in coffee from a moca pot and in coffee by flip-drip method. The biggest part was~made by furfuryl alcohol.
|
|
|
Content of selected alkaloids in tea and coffee
Trenzová, Kristina ; Divišová,, Radka (referee) ; Diviš, Pavel (advisor)
This master thesis deals with content of selected alkaloids in tea and coffee samples. Theoretical part of this paper focuses on basic characteristic of Camellia sinensis and Coffea arabica/canephora, its processing technology and chemical composition. Furthermore, there is discussion about effects of methylxanthines on the human body, the effects on health and metabolism in plants capable of accumulating methylxanthines. The samples were extracted into an organic solvent and also prepared in the aqueous phase according to the recommended preparation. This thesis focuses on xanthine alkaloids - caffeine, theobromine and theophylline. Of the coffees, Robusta coffee from India had the highest caffeine concentration (1730 mg/l), which corresponds to 1,72 % in coffee. From Arabica samples, the highest caffeine concentration was measured for Honduras coffee (1115 mg/l), which is 1,11 %. The highest values of tea samples were measured for Ceylon types, the highest caffeine concentration was measured for black Ceylon 2087 mg/l, which is 2,08 %. The highest concentration of theobromine was in Ceylon gunpowder (175,4 mg/l). Alkaloids passed into aqueous solutions with almost 100 % efficiency, depending on temperature and time. The best penetration was for coffees prepared by a mocha teapot and for pu-erh teas. The worst for green teas and maté samples.
|
|
|
Study of natural antimicrobial mixtures and their stabilization
Vejrostová, Petra ; Veselá, Mária (referee) ; Márová, Ivana (advisor)
Present diploma thesis is focused on natural antimicrobial substances. The aim of the experimental part of thesis was testing of antimicrobial activity of selected natural substances in free and encapsulated forms, preparation of particles and monitoring of their long-term stability. Various teas extracts (aqueous, ethanoic and DMSO) and aqueous herbs extracts were used as plant antimicrobial substances. Liposomes and chitosan particles with encapsulated aqueous teas extracts were prepared by ultrasonication. Encapsulation efficiency, size, stability and antioxidant activity for all particles were specified. Consequently, within a two months period, long-term stability for these particles was monitored. Spectrophotometric method for determining total polyphenols was used for evaluating encapsulation efficiency as well as for monitoring of long-term stability. The DLS method was used for determination of size and stability of particles. Antioxidation activity was monitored by using spectrophotometric method using ABTS. For testing antimicrobial activity of various types of teas, herbs extracts and their mixtures and combianitons with lysozyme and antibiotics, broth dilution methods were used while using both Gram positive and Gram negative bacterial test strains. Antimicrobial activity of prepared particles was also monitored, the antimicrobial activity was especially significant with the chitosan particles. Suitable combinations of natural substances whatever with antimicrobial or antioxidation effect either in free or encapsulated form could be used for applications for example in cosmetics industry, food processing or in medicine.
|
|
|
Use of liquid chromatography to analyze caffeine solutions exposed to plasma
Brabcová, Kristýna ; Řezáčová, Veronika (referee) ; Mravcová, Ludmila (advisor)
This thesis deals with the current problem of increasing concentration of caffeine in water that is connected with caffeine consumption among people. This problem is not that urgent becusase the concentration is not high and for human is not so harmful. The bigger populaton is, the more caffeine people consume and the amount of caffeine in wastewater rises. This fact could be considered as a future problem. An appropriate method effective for elimination of harmful substances are advanced oxidation processes (AOP). Theoretical part describes purine alkaloids with detail desctription of caffeine. Plasma was chosen as a method for caffeine degradation and there are some facts described. There is a chapter about appropriate analytical methods. The samples were picked after periodical time intervals. These samples were analyzed by UHPLC. The results were compared with study dealing with this theme.
|
|
|
Development of method for determination of qualitative parameters of cocoa powder
Vránová, Petra ; Vítová, Eva (referee) ; Vespalcová, Milena (advisor)
The theoretical part of the master’s thesis is focused on a brief botanical characterization of the cacao tree and its most famous varieties discussed. Furthermore, the chemical composition of cocoa beans is described with an emphasis on theobromine and caffeine. There is also mention of the cocoa beans the cocoa bean processing technology for cocoa liquor and cocoa powder, which are then used in food industry. Additionally there is a shorta short description of the legal requirements relating to cocoa. In this part are also two chapters are devoted to the description of instrumentation of high performance liquid chromatography (HPLC) and inductively coupled plasma optical emission spectrometry (ICP-OES). The experimental part deals with analyzes of cocoa powder, cocoa beans, cocoa liquor and waste cocoa beans sold as a "tea mixture". A total of 10 legislation-recommended parameters have been identified in the listed raw materials, such as caffeine, theobromine and sucrose, heavy metal and potassium, fat content etc. The highest content of theobromine was determined in cocoa powder 178.363 mgl-1, caffeine in cocoa beans 16.096 mgl-1. All samples analyzed contained a little amount of sucrose as expected, the highest concentration was found in the tea mixture samples in both the water: ethanol sample of 84.069 mgl-1, and the sample solution in water of 65.897 mgl-1.
|
|
|
Influence of selected coffee bean roasting technology on its chemical composition
Šajdlerová, Kristýna ; Mikulíková, Renata (referee) ; Diviš, Pavel (advisor)
The subject of this diploma thesis is the monitoring of chemical changes taking place in the coffee bean during roasting using various devices. For these purposes an industrial coffee roaster and a home roaster were used in the practical part. The theoretical part deals mainly with the characterization of coffee beans in terms of the content of various compounds and a description of the changes that occur during roasting. Different types of roasting machines are also presented. In the experimental part the roasting of coffee beans and the determination of the concentration of selected substances in the samples taken during roasting were performed. The monitored parameters included the concentration of sucrose, organic acids (citric, acetic, lactic, malic, formic and chlorogenic), caffeine and aromatic substances. One of the biggest differences found between the both roasters is the reduction in the concentration of chlorogenic acid, which decreased by 33 % for domestic equipment, while the decrease was almost doubled for industrial roasters. Another significant difference was also observed in the change in sucrose content. Sucrose degradation occurred in 94 % of coffee bean samples roasted on an industrial roaster, while only 75 % of the second type of roaster.
|
|
|
Encapsulation of caffeine
Patočková, Klára ; Pekař, Miloslav (referee) ; Márová, Ivana (advisor)
This bachelor thesis is focused on possibilities of encapsulation caffeine in micro- and nanoparticles. In the theoretical part was devoted to information about caffeine, liposomes and polysaccharides and also on the techniques of encapsulation. In the experimental part 5 different methods were used for preparation of micro- and nanoparticles with encapsulated caffeine. Caffeine was packaged into liposomes and polysaccharide particles (chitosan/alginate). Encapsulation’s effectiveness was determined by HPLC/UV-VIS. Prepared particles were monitored for size and stability by dynamic light scattering. The particles were exposed to the arteficial stomach and intestinal juices and bile acids. Particle stability and amount of released caffeine was monitored. Analytical centrifugation was used to measurement of sedimentation velocity and stability of the prepared particles. Caffeine containing particles were added in several soft drinks to determine particles amount when turbidity occurred.
|
guest ::
