MODELING OF DESORPTION ISOTHERM OF BLACK TEA

In this paper the relationship between the moisture content of black tea and the relative humidity at different temperature conditions is interrogated. The equivalent moisture contents was measured using the static gravimetric method under the relative humidity range of 10% to 90% and under the temperature range of 25°C to 80°C. The obtained data was analysed using statistical data processing techniques and the results fitted to the different sorption isotherm equations like GAB, Oswin, Henderson, and Halsey at various temperatures. The G.A.B. and Oswin equations show good agreements with the obtained results. The results indicate that the desorption isotherms of black tea are sensitive to the temperature. At constant water activity, an increase in temperature decreases the equivalent moisture content of black tea.