PURIFICATION OF GELATIN BY ULTRAFILTRATION WITH A FORCED SOLVENT STREAM ALONG THE MEMBRANE PERMEATE SIDE - AN EXPERIMENTAL APPROACH

Ultrafiltration of food grade gelatins was performed under various con ditions in a tubular ultrafiltration pilot plant. Firstly, the perform ances in terms of permeate flux as a function of gelatin concentration are presented. Retention performances are also given in terms of rete ntion coefficients. The fluxes were 55 1/h. m2 for low gel strength ge latin, and 25 l/h. m2 for high gel strength gelatin. The retention of gelatin by the membrane was 99% for low gel strength gelatin and 98-99 .5% for high gel strength gelatin. Secondly, the diafiltration techniq ue was applied to gelatin-sodium chloride solutions. When diafiltratio n with a permeate-forced solvent stream was used instead of classical diafiltration, the efficiency was improved. This improvement was found to be a function of the velocity of the solvent along the permeate si de. The maximum observed improvement in terms of diafiltration ratio w as a 43% reduction of this ratio compared to classical diafiltration. Finally, gelatin-sodium chloride solutions were concentrated with and without a permeate-forced solvent stream. When the permeate-forced sol vent stream was employed, the NaCl concentration decreased, while it r emained almost constant during concentration without a permeate-forced solvent stream.