Leaf protein concentration of alfalfa juice by membrane technology

Membrane technology (microfiltration (NW) and ultrafiltration (OF)) of alfalfa juice was studied as an alternative method to conventional leaf protein concentration. Three types of filtration modules (dead end filtration using laboratory Amicon cell (DA), dynamic cross filtration using rotating disk module (CRDM) and dead end filtration using rotating disk module (DRDM)) were used to investigate concentration efficiency of MF and OF with full recycling tests and concentration tests. Rotating speed and transmembrane pressure (TMP) improved flux behavior, but higher permeate flux caused by higher rotating speed reduced leaf protein rejection of MF. The strong rotating shear effect and open flow channel structure of CRDM could control concentration polarization and membrane fouling, therefore, it gave the best flux behavior, least flux decline, best clarification effect, smallest irreversible fouling and highest permeability recovery in membrane cleaning. However, the best leaf protein rejection was obtained by DRDM, because of high shear rate and secondary filtration of fouling layer created by closed flow channel structure. Besides, CRDM showed the highest productivity and best potential for industrial application. These results from laboratory-scale tests can be very useful for concentrating leaf protein from alfalfa juice and serve as a valuable guide for process design in industrial scale. (C) 2015 Elsevier B.V. All rights reserved.