Yussof, Nor Shariffa
(2010)
Enzymatic Hydrolysis Of Native Granular And Modified Starch Below Gelatinization Temperature.
Masters thesis, 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. Both hydrolyzed annealed starches
had more porous granules and rougher surface as compared to native starch due to
enzymatic erosion.
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