Effect of tannase on the color and appaerance of tea extracts prepared from tea fibers

The effects of tannase on the color and appearance of tea extract prepared from tea fibers were investigated in this thesis. Tea fiber extracts were obtained by brewing fibers with water for 15 minutes at 95°C at a tea fiber:water ratio of 1:50. The extracts were treated with commercial tannase at various concentrations (%0.005, %0.25 and %0.5) for different time periods (30, 75 and 120 minutes) at different pH values (pH 2, pH 5 and pH 8) and temperatures (10°C, 20°C, 35°C, 50°C and 60°C). The effects of enzyme concentration, incubation period, pH and temperature on the amounts of tea cream formation in the extracts, water soluble solid contents, turbidity, transmittance, total color and color (L*, a*, b*, chroma and hue) values of the extracts were determined. The amounts of tea cream formation in tannase-treated tea fiber extracts were found to be between 0.002 and 0.085% while the water soluble solid contents were determined to be in the range of 0.52-1.57 °brix. Turbidity, transmittance and total color values of tannase-treated extracts were found to be in the ranges of 3.11-4.61 NTU, 70.88-96.21% and 0.61-2.79%, respectively. Additionally L*, a*, b*, chroma and hue values of enzyme-treated extracts were determined to be in the ranges of 41.38-86.68, 17.14-28.43, 59.36-81.39, 69.91- 88.51 and 63.70-82.63, respectively. The results obtained in the experiments performed on the production of tea fiber extract by using tannase (5000 U/g) showed that the most proper enzyme treatment was the incubation of extract with tannase for 75 minutes at pH 5 and 35°C at an enzyme concentration of 0.5%.