| dc.contributor.advisor |
Kráčmar, Stanislav
|
|
| dc.contributor.author |
Phan, Thi Thanh Dieu
|
|
| dc.date.accessioned |
2013-10-09T10:05:08Z |
|
| dc.date.available |
2013-10-09T10:05:08Z |
|
| dc.date.issued |
2009-02-11 |
|
| dc.identifier |
Elektronický archiv Knihovny UTB |
cs |
| dc.identifier.uri |
http://hdl.handle.net/10563/23060
|
|
| dc.description.abstract |
Kofein (1,3,7-trimethylxanthin) je znám jako stimulant centrální nervové soustavy (CNS). Zrnková káva obsahuje mezi 0,8 až 2,8% kofeinu v závislosti na druhu a původu. Kofein přispívá z 10-30% k hořké chuti kávy. Obsah kofeinu v C. canephora (Robusta) je přibližně dvakrát větší než C. arabica (Arabica). Obsah kofeinu v kávových zrnech se významně nemění v průběhu pražení. Avšak, množství kofeinu v kávě se významně mění v závislosti na typu produktu (Arabica, Robusta, nebo poměru Arabica a Robusta ve směsi), jemnosti mletí, způsobu přípravy (Espreso, turecká nebo filtrovaná káva) a na objemu šálku kávy. Komerčně prodávaná pražená mletá káva může být dostupná na trhu v různém stupni pražení, různé hrubosti mletí, poměru druhů kávových zrn ve směsi, které určují kvalitu produktu. Například, káva Robusta je mnohem méně kvalitní a aromatická než Arabica, ale Robusta je lacinější; takže Robusta je častěji hlavní součástí výsledných komerčních směsí. Obiloviny a sója jsou dokonce často používány jako ingredience vzhledem k jejich láci. Epidemiologické a experimentální studie ukazují pozitivní efekt konzumace kávy na různé zdravotní problémy, jako jsou psycho-aktivní odezvy (pozornost, náladovost), neurologické podmínky (dětská hyperaktivita, Parkinsonova nemoc), metabolické poruchy (diabetes, žlučové kameny) a funkce jater. Avšak vysoké dávky, mohou u některých vysoce sensitivních individuí vyvolávat negativní projevy, včetně stavů úzkosti, tachykardie a nespavosti. Proto je velice významné znát koncentrace kofeinu v kávě. Přestože kofein zaznamenal zvýšenou pozornost vědecké komunity, je jeho působení velmi komplexní, a jak bylo zdůrazněno výše závisí na mnoha faktorech. Proto je velmi zajímavé stanovit obsah kofeinu v komerčně dostupných vzorcích mleté pražené kávy. Úkolem této studie bylo získání více informací o stanovení obsahu kofeinu ve vzorcích mleté pražené kávy z Vietnamu a České republiky. Navíc byla u obou druhů kávy rovněž porovnána vedle obsahu a účinnost extrakce kofeinu. |
cs |
| dc.format |
81 |
|
| dc.format.extent |
2360419 bytes |
cs |
| dc.format.mimetype |
application/pdf |
cs |
| dc.language.iso |
en |
|
| dc.publisher |
Univerzita Tomáše Bati ve Zlíně |
cs |
| dc.rights |
Bez omezení |
cs |
| dc.subject |
mletá pražená káva
|
cs |
| dc.subject |
vietnamská káva
|
cs |
| dc.subject |
česká káva
|
cs |
| dc.subject |
extrakce v systému kapalina/kapalina
|
cs |
| dc.subject |
derivační spektrofotometrie
|
cs |
| dc.subject |
UV/VIS
|
cs |
| dc.subject |
ground roasted coffee
|
en |
| dc.subject |
Vietnamese coffee
|
en |
| dc.subject |
Czech coffee
|
en |
| dc.subject |
caffeine
|
en |
| dc.subject |
liquid-liquid extraction
|
en |
| dc.subject |
derivative spectrophotometry
|
en |
| dc.subject |
UV/VIS
|
en |
| dc.title |
Vliv procesu pražení a přípravy kávy na fyziologii člověka |
cs |
| dc.title.alternative |
The Influence of the Coffee Roasting Process and Coffee Preparation on Human Physiology |
en |
| dc.type |
disertační práce |
cs |
| dc.date.accepted |
2012-06-20 |
|
| dc.description.abstract-translated |
Caffeine (1, 3, 7-trimethylxanthine) is known as a Central Nervous System (CNS) stimulant. Coffee beans contain between 0.8 and 2.8% caffeine - depending on species and origin. It contributes to 10 - 30% of the bitter taste of coffee brews. The caffeine content in C. canephora (Robusta) is about two times that of C. arabica (Arabica). The caffeine content of a coffee bean is not significantly changed during coffee roasting. However, the amount of caffeine in coffee brewing substantially varies according to the type of product (Arabica, Robusta, or ratio of Arabica to Robusta in blending), the grinding degree, brewing methods (Espresso, Turkish or Filter coffee) and the serving size (i.e. cup volume). Commercial ground roasted coffees may be available on the market in different roasting degrees, grinding degrees, ratio of coffee species in blending, on all of which depends the quality of the product. The purpose of this study was to gain more information on the quantitative determination of caffeine content in Vietnamese and Czech ground roasted coffees. The contents and the transfer efficiency of caffeine in the Vietnamese and Czech coffee samples were also compared. In this study, a rapid, simple and cheap UV/VIS Spectrophotometric Method for the quantification of the caffeine content in commercial coffees was developed and validated. The method involved the Direct Method, Standard Addition Method, Extraction in Chloroform, and the 1st Order Derivative Method. In the Direct Method, the coffee sample was measured directly by conventional UV/VIS Spectrophotometry. The concentration of caffeine was calculated from the Regression Equation: (y = 0.0511, r2 = 1), in which y is the absorbance of the sample at 273.2 nm, and x is the concentration of caffeine in the samples. The results showed that the caffeine contents of the coffee samples were found to be out of documented range. In the Standard Addition Method, the coffee sample was measured 4 times with a series of increasing volumes of caffeine standard solution, at 273.2 nm. After measuring the response for a series of standard additions, the concentration of caffeine in the sample was: x = -b/a (míg/mL), when y = ax + b = 0. The results showed that the caffeine contents of the coffee samples were found to be out of documented range. In the liquid-liquid Extraction by Chloroform process, the coffee sample was extracted in chloroform, over 10 minutes. The extraction was repeated 3 times. The combined extract measured was 276 nm. The concentrations of caffeine were calculated from the Regression Equation: (y = 0.0489x, r2 = 1), in which y is the absorbance of the sample at 276.2 nm, and x is the concentration of caffeine in the sample. The results showed that the caffeine contents of the coffee samples were found to be within the documented range. In the 1st Order Derivative Method, the concentrations of caffeine were calculated from the Regression Equation: (y = 0.0483x + 0.0107, r2 = 1), in which y is the peak-to-peak amplitudes of the First Order spectra at the extrema of each sample viz. (Figs. 27-34), and x (míg/mL) is the concentration of caffeine in the samples. The results showed that the caffeine contents of the coffee samples were found to be within the documented range. The caffeine contents in the coffee samples measured by the Extraction in Chloroform and 1st Order Derivative Method were found to be in agreement with those reported in the literature. The caffeine contents were found to be: In Vietnamese Coffee: (0.48 +- 0.01 - 2.10 +- 0.08%); in Czech Coffee: (2.09 +- 0.10 - 2.12 +- 0.06%). Both methods can be used for the determination of commercial ground roasted coffee. |
en |
| dc.description.department |
Ústav analýzy a chemie potravin |
cs |
| dc.description.result |
obhájeno |
cs |
| dc.thesis.degree-discipline |
Technologie potravin |
cs |
| dc.thesis.degree-discipline |
Food Technology |
en |
| dc.thesis.degree-grantor |
Univerzita Tomáše Bati ve Zlíně. Fakulta technologická |
cs |
| dc.thesis.degree-grantor |
Tomas Bata University in Zlín. Faculty of Technology |
en |
| dc.thesis.degree-name |
Ph.D. |
|
| dc.thesis.degree-program |
Chemie a technologie potravin |
cs |
| dc.thesis.degree-program |
Food Chemistry and Technology |
en |
| dc.identifier.stag |
28266
|
|
| dc.date.submitted |
2012-04-26 |
|
