Insoluble alfalfa protein concentrate (APC) was solubilised by two proteolytic enzymes (pepsin and Delvolase) in batch and in continuous flow membrane reactor. In a preliminary investigation, the suitable enzyme (Delvolase) was selected and the nitrogen solubility profile of APC was established. The kinetics of APC solubilization was investigated: no product inhibition was noticed and the enzyme was found to be adsorbed on the APC particles. The effect of operating variables such as enzyme and substrate concentrations, permeate flow, reactor volume and residence time were studied. (C) 2004 Published by Elsevier Inc.