Enzymatic Hydrolysis Of Native Granular And Modified Starch Below Gelatinization Temperature
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Date
2010-04
Authors
Yussof, Nor Shariffa
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
The effects of mild heat treatment, cross-linking and annealing towards the
susceptibility of granular starch to enzymatic hydrolysis at sub-gelatinization
temperature (35ºC) were investigated. Mild heat-treatment was carried out at 60ºC
for 30 minutes. Cross-linking was performed by re-acting the starches with 1%
epichlorohydrin (ECH), while for annealing the starches were annealed at 50ºC for
72 hours. Tapioca and sweet potato starches were subjected to enzymatic hydrolysis
with a mixture of fungal α-amylase and glucoamylase at 35°C for 24 hours. The
dextrose equivalent (DE) value of heat-treated starch increased significantly
compared to native starch i.e. 36% to 50% and 27% to 34% for tapioca and sweet
potato starch, respectively. The DE of cross-linked tapioca starch decreased
significantly from 36% to 28%. Both annealed tapioca and sweet potato starches
were hydrolyzed to a greater degree compared to native starch. Scanning Electron
Microscopy (SEM) examination on hydrolyzed starches showed that enzymatic
erosion occurred mainly at the surface of starch granules. Hydrolyzed heat-treated
starch exhibited rougher surface and porous granules compared to native starch.
SEM micrograph revealed that hydrolyzed cross-linked starches had less porous
granules as compared to their native counterparts.
Description
Keywords
Starch