Purification and characterization of pectinase produced from Apple pomace and evaluation of its efficacy in fruit juice extraction and clarification

Pectinase (Pectin methyl esterase) produced by Aspergillus niger in solid state fermentation of apple pomace using the optimized conditions was partially purified by (NH4)2SO4 fractionation (20-80% concentration). The purified enzyme was found to be stable up to 60 days. It remained heat stable up to 50oC but completely inactivated at 90oC. The partially purified enzyme showed highest activity at pH 3.5. It was also evaluated for juice extraction and clarification of plum, peach, pear and apricot juices. The juice recovery of enzymatically treated pulps increased significantly from 52 to 78% in plum, 38 to 63% in peach, 60 to 72% in pear and 50 to 80% in apricot. Addition of pectinase significantly increased the colour, total soluble solids (TSS), titratable acidity and total sugars in the enzymatically extracted juices. The pH, Brix acid ratio and relative viscosity of extracted juices were decreased. The ascorbic acid content remained unaffected with the increase in enzyme concentration. The overall sensory evaluation of extracted juices using hedonic test showed a significant improvement in their colour and clarity scores. The flavour of the extracted juice remained unaffected by the addition of enzyme at all concentrations. For extraction of juice, 2.5% enzyme concentration was found to be the best. However, for clarification of apple and pear juice 1.0 and 0.5% concentration, respectively gave optimum results. It is concluded that the pectin estrase enzyme produced from apple pomace had desirable activity and improved the quality of evaluated fruit juices.