Clarification of juices

In the fruit juice industry, ultrafiltration membranes find their application mainly in juice clarification processes and associated purifications. Membrane-based techniques are more attractive for food industry because of lower demand in manpower, higher efficiency, shorter processing time, and therefore superior cost-effectiveness, energy consumption, and lower Temperatures compared to traditional filtration techniques (conventional filtration, vacuum evaporation).

Ultrafiltration of juices is normally performed at cross-flow configuration, where the feed flow is directed tangentially to the surface of the membrane. The main advantages of this modality are its scalability and nondenaturing behavior towards delicate materials. Moreover, this pattern of feed flow allows better control over the membrane productivity, as it “sweeps” the deposits of particles formed on the membrane surface due to their rejection.

Juices of different fruits (apple, orange, lemon, kiwifruit etc) may be clarified using membranes. However, due to different composition of feed solution, the operating conditions (feed flow rate, membrane sieving properties, membrane module design, cleaning frequency etc) should be accurately optimized to insure the most efficient process. For example, often the membrane with cut-off below 25 kDa should be selected, otherwise tannins can pass into the clarified juice, leading to a brownish color and sharp flavor.