Preparation and properties of an immobilized pectinlyase for the treatment of fruit juices

Pectinlyase, present in different commercial pectinases used in juice technology, was immobilized on alginate beads. The optimal conditions were: 0.17 g alginate ml−1, 1.2% (w/v or v/v) enzyme concentration and acetic–HCl/glycine–HCl buffer at pH 3.6 or tris–HCl/imidazole buffer at pH 6.4. Maximum percentage of immobilization (10.6%) was obtained with Rapidase C80. Kinetic parameters of free and immobilized pectinlyase were also determined. The pH and temperature at which activity of soluble and immobilized enzyme was maximum were 7.2 and 55 °C. Thermal stability was not significantly altered by immobilization, especially at 40 °C, showing two periods of different stability. Free and immobilized preparation reduced the viscosity of highly esterified pectin from 1.09 to 0.70 and 0.72 mm2 s−1, respectively, after 30 min at 40 °C. Furthermore, the immobilized enzyme could be re-used through 4 cycles and the efficiency loss in viscosity reduction was found to be only 9.2%.