Optical and Thermal Properties of Coffee and Caffeine
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Date
2005-06
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Addis Ababa University
Abstract
In this project, the thermal and optical propeliies of coffee and caffeine are investigated.
Characteristics involved are solvatochromic effect, fluorescence, chemical structures (bonds) and
thermal propeliies of both coffee and caffeine. The UVNis absorption band of caffeine in
different solvents shows very small solvatochromic effect, indicating only local transitions of
electrons. This founding is similar to that found for QM-calculations. Fluorescence
measurements revealed no fluorescence emission by caffeine, but deactivation of fluorescien
fluorescence intensity. However, simple cOlTelation between the deactivation produced by
caffeine and coffee on the fluorescence of fluorescein could not be drawn with out the detailed
know ledge of other components. From FT -IR results, the fluorescence deactivation mechanism
is found to incorporate carbonyl groups of both caffeine and coffee. The observed thelTl1al
(TGA) results showed coffee is thermally unstable and decomposes steadly.This shows the
inherent discrepancy of the temperature dependent measurement, which makes exact
measurement of caffeine at various temperature intervals unrealistic. The DSC result shows
crystallization, heat absorption melting and heat release of coffee at various temperature regions
Key Words: Coffee, Caffeine, Fluorescence, Solventochromism, Thermal, UVNis
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Keywords
Coffee, Caffeine, Fluorescence, Solventochromism, Thermal, UVNis