Factors Affecting Browning of Sago (Metroxylon Sagu Rottb.) Pith and Their Effects on Sago Starch
The effect of four parameters on the browning of sago pith was evaluated i.e. maturity of the sago palm, and holding time, pH and temperature of the sago pith slurry. The effect of sago palm maturity on the browning of sago pith was determined using sago pith slurries from three maturity stages i...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2002
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/8479/1/FSMB_2002_16_IR.pdf http://psasir.upm.edu.my/id/eprint/8479/ |
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| Summary: | The effect of four parameters on the browning of sago pith was evaluated i.e.
maturity of the sago palm, and holding time, pH and temperature of the sago pith
slurry. The effect of sago palm maturity on the browning of sago pith was determined
using sago pith slurries from three maturity stages i.e. young, premature and mature.
The sago palms were sectioned into top and bottom to examine the effect of trunk
growth on the concentrations of soluble phenolic compounds. Two soluble phenolic
compounds were found to be present in the sago pith i.e. (+)-catechin and
(-)-epicatechin. Concentrations of (+)-catechin and (-)-epicatechin were higher in
mature sago palms while distribution of these compounds with trunk gowth did not
show a clear correlation. Soluble polyphenol oxidase (SPPO) activity increased while
latent polyphenol oxidase (LPPO) activity decreased with increase in maturity of the
sago palms. Colour development in the slurry monitored in terms of lightness (L) and
redness (a) using the HunterLab Ultrascan Spectrocolorimeter was more intense
(darker and redder) in mature sago palms.The effect of holding time, pH and temperature of the sago pith slurry was
studied using a mature sago palm. Browning was evaluated based on concentrations
of (+)-catechin and (-)-epicatechin and colour development in the sago pith slurry. The
effect of holding time (duration for which sago pith slurries were held) on the browni ng
of sago pith slurry was studied for 1, 6, 12 and 24 hours. An increase in holding time
resulted in significant (P<0.05) decreases of (+)-catechin and (-)-epicatechin. Colour
development in the slurry was significantly (P<0.05) more intense with increased
holding time but was not significant (P<0.05) after six hours. The effect of pH on the
browning of sago pith was studied using sago pith slurries with pH from 3.5 to 7.0 with
a holding time of 24 hours. Concentrations of (+)-catechin and (-)-epicatechin
decreased significantly (P<0.05) with an increase in pH particularly between pH 5.0
and 6.5 which resulted in significant (P<0.05) colour development. The effect of
temperature on the browning of sago pith was investigated using sago pith slurries with
temperatures from 10°C to 50°C with a holding time of 24 hours . The amount of
(+)-catechin and (-)-epicatechin decreased significantly (P<0.05) with the increase in
temperature while colour development increased significantly (P<0.05) with
temperatures particularly above 40°C.
The quality of sago starch extracted from slurries with different pH and
temperatures and held for 24 hours was determined. Starch quality was determined in
terms of colour development, granule morphology and pasting profile. Significant
(P<0.05) colour development was noted in starches extracted from slurries of different
pH and temperatures though they were washed twice during extraction. Granule
morphology of the starches was observed using the Scanning Electron Microscope.
Starches from slurries of strong acidic (pH 3.5 to 4.5) conditions exhibited fissures on
the surface of granules while those from weaker acidic (pH 5.0 to 7.0) conditions had minor protrusions. Starches from slurries at different temperatures had only minor
modifications on the surface of the granules. The pasting profile of the starches was
examined using the Brabender Viskograph. Starches from strong acidic conditions
showed lower viscosities while starches from high temperatures (30°C to 50°C) were not greatly affected. |
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