Production of concentrated kiwifruit juice by integrated, membrane process

The concentration of fruit juices is industrially performed in order to reduce storage, packaging, handling and shipping costs. This paper describes the research efforts to develop and optimise an integrated membrane process, on laboratory scale, for the production of concentrated kiwifruit juice as alternative to the traditional vacuum evaporation. Fresh depectinated kiwifruit juice was previously clarified by ultrafiltration (UF) process. 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. Clarified kiwifruit juice was produced in experimental tests carried out according to the batch concentration mode working in optimal operating and fluid dynamic conditions. The osmotic distillation (OD) process was used to concentrate the clarified juice up to a total soluble solids (TSS) content higher than 60 degreesBrix at 25 degreesC. The effect of various operating parameters on vapour flux was studied. An average evaporation flux of almost 1 kg/m(2) h was obtained using a calcium chloride dihydrate at 60 w/w% as brine solution. The effects of UF and OD processes on the total antioxidant activity (TAA) and other analytical parameters of the kiwifruit juice were also studied. A little reduction of the TAA was measured during the membrane treatment; vitamin C content was well preserved in the concentrated juice. On the basis of the results obtained on laboratory scale an integrated membrane process scheme for the clarification and the concentration of kiwifruit juice is proposed.