Preparation and Characterization of Hydroxypropylated Sago Starch
Sago starch was hydroxypropylated with propylene oxide at 40°C in an alkaline medium containing sodium sulphate. In this study, the level of propylene oxide (0-14%), sodium hydroxide (0-2%), sodium sulphate(0-30%), reaction time (8-24 hrs) and reaction temperature (20-50°C) were varied to produce...
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| Format: | Thesis |
| Language: | English English |
| Published: |
1998
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/8392/1/FSMB_1998_10_A.pdf |
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| Summary: | Sago starch was hydroxypropylated with propylene oxide at 40°C in an
alkaline medium containing sodium sulphate. In this study, the level of propylene
oxide (0-14%), sodium hydroxide (0-2%), sodium sulphate(0-30%), reaction time
(8-24 hrs) and reaction temperature (20-50°C) were varied to produce various
samples of hydroxypropylated sago starch. The molar substitution (MS), which is
the amount of substitution that has occured during hydroxypropylation and the
pasting properties were measured for each sample. Increase in the amount of
propylene oxide, sodium sulphate and sodium hydroxide, reaction temperature and
reaction time progressively increased the molar substitution of the modified peak viscosity and the hot paste viscosity. However, the gelatinization
temperature, the consistency of the hot paste viscosity after holding at 95°C and
the setback value was decreased. Highest molar substitution of 0.41 was observed
at 1.5% sodium hydroxide at which the highest peak viscosity and breakdown
with the lowest setback value was also observed. The peak viscosity, cold paste
viscosity and breakdown was highest at 25% sodium sulphate concentration. The
maximum level of hydroxypropylation was observed at 10% propylene oxide,
1.5% sodium hydroxide, 25 % sodium sulphate, at 24 hours reaction time and at
40°C.
In another study, hydroxypropylated sago and corn starch were prepared
by reaction with propylene oxide in an alkaline medium containing sodium
sulphate at 40°C and its physicochemical characteristics were studied and
compared with the native starches. Some of the physicochemical characteristics
evaluated were : pasting properties, molar substitution, swelling power and
solubility, water holding capacity, gel strength, sediment value, light
transmittance, acid and heat stability, starch damage and freeze-thaw stability. In
addition, the morphology of the starch granules were also observed.Hydroxypropylation increased the swelling power and solubility, water
holding capacity and freeze-thaw stability of both starches. The swelling power of
sago starch increased from 33.69 ± 3.92 % to 60.44 ± 2.72% when it was
hydroxypropylated. As for com starch the swelling power increased three times
higher from 8.67 ± 0.056 % for native com to 24.99 ± 1.039% for
hydroxypropylated com. The water holding capacity of native sago was 11.00 ± 0.12% and it further increased to 17.23 ± 0.25% when it was hydroxypropylated.
As described in the literature, it was found that hydroxypropylation increased the
freeze-thaw stability of the sago and com starches. The gel strength of the
starches decreased when it was hydroxypropylated and the values were 56.5 ± 2.12%, 11.5 ± 0.71%, 84.5 ± 2.12% and 46 ± 1.42% for native sago,
hydroxypropylated sago, native com and hydroxypropylated com respectively. The
percentage of starch damage was only 0.02% when sago starch was
hydroxypropylated but for com the starch damage was 2.64% when it was
hydroxypropylated. The sediment value of native sago (96.25 ± 1.0%), was the
highest followed by hydroxypropylated sago starch (94.54 ±0.57%),
hydroxypropylated com starch (67.17 ±0.57%) and native com starch (27.0 ±
2.6%) respectively. Both starches when hydroxypropylated showed no
improvements in their acid and heat stability. |
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