Immobilization of pectinases into calcium alginate microspheres for fruit juice application

In this study, polygalacturonase (PG) was immobilized in calcium alginate microspheres prepared using endogenous emulsification method and its application in apple juice clarification was evaluated. Preparation conditions of calcium alginate microspheres prepared by endogenous emulsification were optimized, additionally, the formed microspheres were characterized. Under optimal conditions, microspheres with the particle size of 38.0 ± 0.2 μm showed good sphericity, storage stability and a narrow particle size distribution. Meanwhile, single factor experiment and response surface experiment were combined to get the optimum conditions of immobilizing PG. The immobilized enzyme presented the optimum temperature at 60.0 °C, which was almost 10.0 °C higher than the free PG and the activity was less dependent upon pH within the interval of 3.0–4.5 than free enzyme, supporting the immobilized enzyme more stable in apple juice clarification (pH = 4.3 ± 0.1). The immobilized enzyme also exhibited good operational stability and 63.0% of its initial activity retained after three batch reactions. In the present of the immobilized PG, the turbidity of apple juice decreased, as well as apple juice had good thermal and freezing ability.