An experimental investigation has been undertaken to observe the effect of external electric field on the enhancement of permeate flux during clarification of mosambi (Citrus sinensis (L.) Osbeck) juice by ultrafiltration. A detailed study has been carried out using a 50 kDa molecular weight cut-off flat sheet polyethersulfone membrane in cross-flow ultrafiltration under laminar flow conditions for a wide range of operating conditions. Use of d.c. electric field resulted in a 32% enhancement of permeate flux. A steady state gel polarization model has been applied to evaluate the gel layer concentration, effective diffusivity and effective viscosity of the juice within the concentration boundary layer, by optimizing the experimental flux data. (c) 2008 Elsevier Ltd. All rights reserved.