Pectin extraction from pumpkin with the aid of microbial enzymes

An optimised procedure is reported for extraction of pectin from pumpkin pulp, using an enzyme preparation from Aspergillus awamori. In contrast to pumpkin pectin obtained previously by digestion with cell-free culture medium from Bacillus polymyxa, the material prepared in the present work forms gels with 60 wt% sucrose at pH 3, although the yield is somewhat lower (14% in comparison with 22%). The main action of the enzyme complex from A. awamori is to degrade cellulose and other insoluble constituents of the plant tissue, but it also has some pectinesterase activity, which could allow degree of esterification (DE) to be manipulated by varying digestion time. The time used in this investigation (3 h) gave a DE of 53%; reduction in DE at longer times should yield pectin with a higher content of unesterified galacturonate residues, capable of binding lead and other heavy-metal cations. Some possible medicinal and food uses are suggested.