Optimization of Process Parameters for Water Extraction of Stevioside using Response Surface Methodology

Hot water extraction process was used for the extraction of steviosides from dry stevia leaves. The independent variables were, leaf to water ratio (1:5 to 1:20), heating time (10 to 120 min), and temperature (30 to 90°C). The combined effects of these independent variables on the extracted stevioside concentration and color of the extract were studied. For optimizing the extraction process, central composite rotatable design in combination with response surface methodology was used. Significant regression models with coefficient of determination greater than 0.90 were established to study the effect of independent variables on the responses. The optimum conditions are: temperature of water: 78°C, time of heating: 56 min and leaf to water ratio: 1:14 (g:mL).