Cross-flow filtration of pectic substances during the enzymatic treatment of mandarin segment membranes

This study is concerned with the cross-flow filtration of pectic substances, produced by the enzymatic treatment of membranes of mandarin segments, using several filtration membranes with pore sizes of between 0.45 μm and 30 kDa. Pectic substances solubilised in the digestion medium were polymers with an average molecular weight of 90–100 kDa. Pectin was retained by the membrane with a 100-kDa pore size. As a result of the addition of enzymes, pectin was degraded to a mixture of galacturonic acid and galacturonic acid oligomers, which appeared to be distributed between the retentate and the permeate. The final filtration rate of galacturonic acid oligomers was close to 100% when enzymes were present at the filtration membranes. In the absence of enzymes, the filtration rate ranged from 5% to 15%, and the permeation flux tended to decrease. The enzymatic treatment had an important effect on the resistances of the filtration membranes, and also caused a decrease in viscosity. These two factors were responsible for the increase in the permeate flux after the addition of enzymes, where this flux was almost as high as when filtration commenced.