ABSTRACT The effect of alteration in hydrodynamic conditions and external electric field on the permeate flux during ultrafiltration of synthetic and mosambi juice in a cross flow channel has been studied. The hydrodynamic conditions inside the cross flow channel were altered by imposing laminar flow, laminar flow with turbulent promoters, flow in the transition (in case of synthetic juice) and turbulent (in case of actual juice) regime. The steady state permeate flux was in the range of 17.5 to 18.5 L/m2h (at Re = 657, laminar flow) for operating pressures (276 to 552 kPa). This range was in between 18 and 22.5 L/m2h using turbulent promoters at the same Reynolds number and in between 35 and 43 L/m2h in the transition flow regime at the same operating pressure. In the third case, the effects of external electric field (a body force) on the flux enhancement were explored. The steady state flux of the synthetic juice increased by about 20% when the external electric field was applied gradually up to 1,600 v/m. For actual depectinized mosambi juice, about 50% enhancement of steady state flux was achieved with an external electric field of strength 500 v/m. PRACTICAL APPLICATIONS The application of membrane technology to fruit juice processing is one of the emerging areas in food industry. Ultrafiltration (UF) and microfiltration (MF) processes are valid approaches for the clarification of fruit juices. The traditional method of fruit juice clarification involves a number of steps involving centrifugation to remove suspended solid, enzymatic treatment for depectinization, fining agents such as bentonite, gelatin to remove haze and finally filtration by the diatomaceous earth to remove the fining agents. The major problem during juice clarification is the pectin present in juice even after the enzyme treatment, leading to a drastic flux decline during UF and MF. In this study, two methods, namely, alteration of hydrodynamic conditions in the flow channel and application of external electric field for improving the permeate flux during UF of synthetic as well as depectinized mosambi juice, are investigated.
Department of Agricultural EngineeringBirsa Agricultural UniversityKanke, Ranchi, India 2:
Department of Agriculture and Food EngineeringIndian Institute of Technology, KharagpurKharagpur- 721 302, India 3:
Department of Chemical EngineeringIndian Institute of Technology, KharagpurKharagpur- 721 302, India