Protein-Hydrocolloids Interactions in "Keropok Lekor"
Basic formulation of 'keropok lekor' was developed through a sensory evaluation exercise. A fish to starch ratio of 3:2 and a ratio of sago to tapioca starch of 3:l were found to be the best formulation. The optimum levels of salt L and sugar in the formulation were 2.5% and 3.8%, base...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2004
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/6688/1/FSMB_2004_13.pdf |
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| Summary: | Basic formulation of 'keropok lekor' was developed through a sensory
evaluation exercise. A fish to starch ratio of 3:2 and a ratio of sago to tapioca
starch of 3:l were found to be the best formulation. The optimum levels of salt
L
and sugar in the formulation were 2.5% and 3.8%, based on total weight of
fish and starch, respectively. Effect of selected hydrocolloids i.e. xanthan,
carrageenan and locust bean gums at 0,1,2, and 3% of incorporation on
acceptability, structure stability and shelflife of 'keropok lekor' was also
studied. Incorporation of 2% locust bean gum significantly increased the
sensory acceptability and structure stability of final product. The shelf life of
the 'keropok lekor' gel was also enhanced by the incorporation of 2% locust
bean gum by 4 day.
Addition of all the hydrocolloids increased gelatinization temperatures of sago
starch by 4-6°C and decreased the enthalpy (AH) of the gelatinization by 0.5
to 2.3Jlg. The AH of gelatinization of sago starch with the addition of xanthan gum was significantly lower than that containing locust bean or carrageenan
gums. The starch gelatinization enthalpy (AH) of the dough containing locust
bean gums was the highest among the hydocolloids.
The effects of the hydrocolloids on hardness of gel and viscoelastic properties
of 'keropok lekor' dough were significantly (P<0.05) dependent on the water
binding ability of the gel. The maximum value of loss (G") and storage (G')
moduli of mixtures of locust bean-starch and carrageenan-starch increased
with the concentration of the gum. However, these moduli decreased in the
xanthan gum-starch mixture. The G' of the 'keropok lekor' dough containing
1% and 2% of locust bean and carrageenan gum were higher than that of
control and xanthan gum incorporated in the temperature range of fish protein
denaturation (from 30 to 76°C). In doughs with 3% incorporation of
hydrocolloids, the G' of the dough incorporated with xanthan gum was found
to be the highest. However the peak modulus (G') at gelatinization
temperature (862°C) of 3% xanthan gum was much lower than that of others.
Thus, the textural properties of the 'keropok lekor' incorporated with 3%
xantan gum were the lowest among the samples.
Examination of the microstructure by light (LM), scanning electron (SEM) and
transmission electron (TEM) microscopy indicated that there were interactions
between starch, fish protein, and hydrocolloids. The results from SEM studies
showed that the sizes and number of cavities were reduced in 'keropok lekor'
incorporated with locust bean and carrageenan gum. Thus, carrageenan and
locust bean gums increased the textural properties such as hardness, cohesiveness
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and springiness of 'keropok lekor'. In contrast, xanthan gum
disrupted the protein networking in the 'keropok lekor' gel, and caused the
formation of larger size cavities as observed in SEM, and reduced the size of
swollen starch granule in the gel matrix as observed in light micrograph. As a
result, xanthan gum significantly decreased the hardness, cohesiveness and
springiness of 'keropok lekor'. Among the 3 hydrocolloids evaluated in the
present study, locust bean gum was the most effective in increasing the
water-binding ability and viscoelastic properties, and it decreased the sizes
and numbers of the cavities in the gel that influenced the textural
characteristics of the final product. Xanthan gum interfered with the gelation - -
process and significantly decreased the viscoelastic properties of the product. |
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