Integrated membrane process for the production of concentrated kiwifruit juice

Aim of this work was to develop and optimise an integrated membrane process for the production of concentrated kiwi fruit juice with high nutritional value. The ultrafiltration (UF) process was previously used to clarify the raw juice. In experimental tests performed according to the total recycle mode the effect of transmembrane pressure, axial flow-rate and temperature on permeate fluxes were studied. Experimental tests carried out according to the batch concentration mode, working in optimal operating and fluid dynamic conditions, were also performed. The clarified juice was concentrated up to about 65 °Brix by osmotic distillation (OD). On the basis of the results obtained on laboratory scale an integrated membrane process scheme for the clarification and the concentration of kiwi fruit juice was proposed. During the UF process the Total Antioxidant Activity (TAA) was maintained, with respect to the fresh juice, both for the permeate and for the retentate. The subsequent concentration treatment by OD did not induce other significative changes to TAA independently from the final concentration obtained.