Enzymatic Hydrolysis Of Native Granular And Modified Starch Below Gelatinization Temperature

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Date
2010-04
Authors
Yussof, Nor Shariffa
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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.
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Starch
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