Clarification of Jerusalem Artichoke Extract Using Ultra-filtration: Effect of Membrane Pore Size and Operation Conditions

Jerusalem artichoke is an important plant for industrial inulin production. Jerusalem artichoke extract was clarified by ultra-filtration. Tests were performed to investigate effects of membrane pore size and operation conditions (trans-membrane pressure and rotation speed) on filtration kinetics and membrane-fouling mechanism. Membrane fouling was proved the main filtration resistance for a 20-kDa membrane, while concentration polarization-induced resistance was dominant for 30-, 50-, and 100-kDa membranes. Despite their similar filtration behavior, the 50-kDa membrane, compared to the 100-kDa membrane, led to less protein content (impurity) in the filtrate. Studies with the rotation speed varied from 0 to 1600 rpm and trans-membrane pressure from 0.2 to 0.4 MPa demonstrated that stirring was essential for elimination of membrane fouling. Competition of driving force and fouling was justified when trans-membrane pressure increased from 0.3 to 0.4 MPa. Filtrate analysis including protein removal, turbidity, and inulin purity revealed that ultra-filtration using the 50-kDa membrane with a trans-membrane pressure of 0.3 MPa and a rotation speed of 800 rpm was able to clarify the Jerusalem artichoke extract, removing 99% protein, and obtain a filtrate with inulin purity of 98%.