Studies On Integrated Membrane Separations For Orange Juice Processing

Clarification and concentration of orange juice by ultrafiltration (UF) and osmotic distillation (OD) was studied in this paper. The experiments mainly investigated effects of operative conditions on the permeate flux, the influence of different membrane process on physico-chemical characteristics of orange juice. Main results indicated as follows:1. Clarification of orange juice by ultrafiltration (PCI corporation, Eng ) was studied by using tubular ES100, 000 and ES25, 000 daltons molecular weight cut-off (MWCO) membrane. The results established that the ES25,000 ( MWCO ) was suitable for clarification.2. Under the condition of full-circumfluence, the flux change rule of orange juice in ultrafiltration process was studied. The results showed that permeate flux increases with pressure up to a limiting value 1.05MPa. A mass transfer equation of orange juice is established as J=14.811n(26.52/C_b)3. The optimum condition's for the clarification of orange juice using ES25,000 were feed flow rate 1.3m³/h and transmembrane pressure 1.0MPa at 25±1℃. The results showed that flux decreased with operating times, the initial flux is higher 20L/m²Â·h, due to gel formation, the permeate flux decreased about 57% of initial. Vc and flavor has part losing, other main nutrition elements such as sugar and organic acid have no evident difference between UF juice and original juice. UF removed some protein and pectin, so the clarified juice was very clear with the transmittance of 98%. After cleaning the membrane module using sodium hydroxide solution of 0.5% (W/W) , the water flux of the fouled membrane was recovered.4. During the OD concentration process, CaCl₂ (55%W/W ) was chosen as stripping solution. Glucose solution was chosen as simulating orange juice. The OD flux decay as the feed concentration and viscosity increasing. The OD flux increase as the feed velocity and brine velocity increasing, During the time, the OD flux decrease from 0.35kg/m²Â·h to 0.087 kg/m²Â·h.5. Based on above research, orange juice was clarifiled using UF and then concentrated by OD process. The results showed that Integrated membrane separation can produce high concentrated orange juice (63°Brix) , preserve better the quality of the raw material, except for losing some Vc about 22%.6. Sensory quality tests and gas chromatographic date show that UF and OD can preserve flavor superior to vacuum concentrated.