Induction of softening in apple flesh by cell wall degrading enzymes produced by Aspergillus niger
Wilawan Kumpoun and Yoshie Motomura
Proceedings of the APEC symposium on postharvest handling systems Bangkok, Thailand September 1-3, 2003. p. 327
2003
บทคัดย่อ
Induction of softening in apple flesh by cell wall degrading enzymes produced by Aspergillus niger
Factors affecting on the activities of cell wall degrading enzymes produced by A. niger and their effects on the softening of apple flesh were investigated. Activities of polygalacturonase (PG), pectineesterase (PE), galactosidase (GALase) and arabinosidase (ARAase) were detected in crude pectinase preparation. In Na acetate buffer, softening of apple flesh discs induced by crude pectinase preparation was accelerated in low pH and high temperature. Cell wall degrading enzymes in the crude enzyme preparation were separated and effect of each enzyme on the softening was tested. At least 4, 3, 4 and 2 isozymes of PG, PE GALase and ARAase were detected, respectively. Among these enzymes, PG showed comparatively high specific activity. Among PG isozymes, only PG was the main enzyme to induce softening of apple flesh disc, with a few amount of activity. GALase and ARAase had no effect on the induction of softening of apple flesh. However, they could accelerate softening when combining with PG. ARAase was much more effective to accelerate softening of apple flesh than GALase. These results suggested that for the softening of fruit flesh by infection of A. niger, degradation of uronate polymers of fruit cell wall polysaccharide by PG was accelerated by ARAase and GALase due to removing of neutral sugars from the pectic polymers. It has been reported that each enzyme could induce softening of fruit flesh, but the combination effects of these enzymes should be investigated.