Pulp—serum separation

Pulp-Serum Separation. As for freeze concentration, high viscosity contributes to limiting the degree of concentration which can be achieved by membrane concentration. Since the insoluble solids present in citrus juices contribute significantly to viscosity, one consideration for process development is to separate the pulp from the clear serum, prior to concentration. Because consumers recognize that citrus juices are cloudy and contain pulpy material, it becomes a requirement to blend the separated pulp back with the product concentrate (31). 

Because no general theories exist even for concentrated non-food suspensions of well defined spherical particles (Jeffrey and Acrivos, 1976 Metzner, 1985), approaches to studying the influence of the viscosity of the continuous medium (serum) and the pulp content of PF dispersions, just as for non-food suspensions, have been empirical. In PF dispersions, the two media can be separated by centrifugation and their characteristics studied separately (Mizrahi and Berk, 1970). One model that was proposed for relating the apparent viscosity of food suspensions is (Rao, 1987) ... 

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