Primary Clarification of Stevia Extract: A Comparison Between Centrifugation and Microfiltration

Abstract

Two clarification processes, namely, centrifugation and microfiltration were used for primary clarification of crude stevia extract. The optimized condition (speed and time) of centrifugation was obtained using response surface methodology. Microfiltration was carried out using a 0.2 µm pore size membrane at different operating pressures (138, 207, 276 kPa) and stirring speeds (500, 1500 and 2500 rpm). Clarified stevia extract was analyzed in terms of color, clarity, total solid and stevioside content. Performance of both of these methods was compared based on the quality of clarified extract. 89.5% stevioside was recovered at 5334 g centrifugation speed with 25.6 minutes of centrifugation. During microfiltration, severe flux decline was observed. At 138 kPa and 500 rpm, the flux decline was 87% within 5 minutes of filtration. This was more severe at higher transmembrane pressure drop and it was 89% at 276 kPa under same stirring. Stirring speed increased the flux significantly. After 25 minutes, at 138 kPa, 2.4 times flux enhancement occurred when stirring speed increased from 500 to 2500 rpm. Recovery of stevioside was more at lower operating pressure and about 89% recovery was attained at 138 kPa.