Class: BE210
Group: W6
Members:

Date: May, 2002

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Abstract:
Spectronic Genesys 5 spectrophotometer was used to determine the influence of brewing tea in different environments such as different pH, temperatures, deionized and tap water. 3 main types of tea, black, green and oolong were used. Also varying grades of tea were compared. Brewing tea in different pHs and in tap water causes a change in the peak absorbance of the wave spectra. At pH of 6 and 8, the peak absorbance was lower than when brewed in deionized water. In tap water, the shape of the curve as well as the peak absorbance is changed. Hence, brewing the tea in tap water or solutions of different pH affect the taste of tea.  By comparing the wave spectra patterns of high-grade and low-grade teas brewed at 500C, it was found that high-grade tea had a lower peak at absorbance than low-grade tea. This could be because in the processing of high-grade tealeaf, compounds that are deemed low grade are removed, resulting in a low peak absorbance. Both caffeinated and decaffeinated black and green teas were tested and the molar extinction coefficients of the extracted caffeine were determined to be 0.89 + 0.086 mol/L.cm and 0.84 + 0.067 mol/L.cm, respectively.  The 2 molar coefficients of caffeine extracted from tea, ?1 and ?2, were found to be statistically similar to that of the molar coefficient of pure caffeine solution, ?3 (0.93 + 0.023 mol/L.cm), at 95% confidence.  Also, Caffeine concentration in black tea is 33.3% higher in black tea, with a caffeine concentration of 0.0064 + 0.0000149 g/L compared to 0.0048 + 0.0000111 g/L in green tea.