Time Dependence of Caffeine in Coffee using Optical Method
| dc.contributor.advisor | Asfaw Araya (PhD) | |
| dc.contributor.author | Wakgari Tesfaye | |
| dc.date.accessioned | 2018-07-05T12:32:44Z | |
| dc.date.accessioned | 2023-11-09T11:24:29Z | |
| dc.date.available | 2018-07-05T12:32:44Z | |
| dc.date.available | 2023-11-09T11:24:29Z | |
| dc.date.issued | 2006-06 | |
| dc.description.abstract | In this project optical properties of pure caffeine, i.e., time dependency of caffeine in coffee powder and solution kept under different conditions and temperatures were inyestigated. FOI' the pure caffeine molar decadic absorption coefficient and transitional dipole moment were computed and found to be (1095 ± 37) m2 mol-I and (I \.3 ± 0.2).\0-30 C m. Respectively in all the systems and temperatures caffeine in coffee was investigated , a decrease in caffeine concentration as a function of time was observed. For the solution both in closed and open storage conditions the pseudo zero order kinetics was observed. The rate constant of decomposition k" = 2.41667xI0-5 mol m-3 hr-I for closed system and kJ = 5.50417xI0-5 mol m-3hr-1 for open system were determined. The linear regression coefficient values were above R = 0.99 in both cases. The half-life time of caffeine were 1177 hI' and 517 hI' for closed and open systems, respectively. In the contrary, for open powder system the kinetics obeyed the expected first order rate expression. For open powder coffee the monoexponential fits resulted in rate constant of decay at room temperature (23°C) and in ambient atmosphere is computed to be k" = 2.4xI0-4 111.-1 and half-life time of caffeine is 289 hI', which implies again chemical reaction during half-life was fastest for powder form storage than other conditions. Reaction rate was faster, as expected, for storage at 23°C than 8°C Key words: Caffeine, Coffee, Spectrophotometer, Pseudo Zero-Order, Monoexponential fit | en_US |
| dc.identifier.uri | http://10.90.10.223:4000/handle/123456789/6720 | |
| dc.language.iso | en | en_US |
| dc.publisher | Addis Ababa University | en_US |
| dc.subject | Caffeine | en_US |
| dc.subject | Coffee | en_US |
| dc.subject | Spectrophotometer | en_US |
| dc.subject | Pseudo Zero-Order | en_US |
| dc.subject | Monoexponential fit | en_US |
| dc.title | Time Dependence of Caffeine in Coffee using Optical Method | en_US |
| dc.type | Thesis | en_US |