National Repository of Grey Literature 5 records found  Search took 0.01 seconds. 
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.
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.
Stanovení kofeinu a jeho metabolitů pomocí HPLC/MS
TESAŘÍKOVÁ, Kateřina
Caffeine is probably the most frequently ingested drug in the world. A lot of people consume caffeine every day in beverages like coffee, tea and soft drinks. In human body caffeine is enzymatically transformed to a lot of metabolites and the first metabolic reactions lead to theophylline, theobromine and 1,7-dimethylxanthine. Consequently, caffeine and its metabolites can be found in human urine or plasma. This thesis deals with the development, optimization and validation of an analytical method for the determination of caffeine ant its metabolites by HPLC/MS. The composition of the mobile phase and settings of mass spectrometry detector were optimized. These steps led to the separation of analytes and to the achievement of stable and intense signal of the detector. An appropriate concentration range for each analyte according to the FDA rules was found. The method was used for the quantification of urinary content of caffeine, and its three metabolites.
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.
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.

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