Effects of broken rice and taro root as sources of starch on the physical properties and microstructure of extruded fish feed
Currently, Malaysia has great dependency on imported starch in production of floating fish pellets. The discovery of alternative sources of starch that are locally grown would promote a sustainable aquaculture feed industry in Malaysia. This study has examined the effects of native and modified s...
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| Format: | Thesis |
| Language: | English |
| Published: |
2014
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/70294/1/FP%202014%2058%20-%20IR.pdf http://psasir.upm.edu.my/id/eprint/70294/ |
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| Summary: | Currently, Malaysia has great dependency on imported starch in production of
floating fish pellets. The discovery of alternative sources of starch that are locally
grown would promote a sustainable aquaculture feed industry in Malaysia. This
study has examined the effects of native and modified starches (broken rice and taro)
and varying extrusion processing variables on the physical properties of the pelleted
fish feed. In the first part of the study, the factors studied were the effects of broken
rice and taro inclusion (15%, 20%, and 25%), moisture level (30%, 35%, and 40%),
and die head temperature (140, 150, 160 and 170°C) on the physical properties of
the extruded pellets. The three barrel zones (70, 90,100°C) and screw speed (150
rpm) of the extruder were set constant throughout the extrusion process. All diets
were processed using a single screw extruder. The findings showed that increasing
broken rice and taro inclusion level, moisture level and die head temperature resulted
in significant improvements on the physical properties of the extruded pellets. At
25% taro and broken rice starch level, 40% moisture level and 170°C die head
temperature, the extruded pellets were able to float for more than 20 minutes.
Likewise, as the die temperature was elevated the taro and broken rice starch have
undergone a high degree of gelatinization evidenced by pellets with increased
expansion ratio and better water stability as noted in water absorption and solubility
indices values. In the second part of the study, two factorial experimental design
were applied to investigate the effects of modified broken rice and taro inclusion
level (15, 20, and 25 %) and extrusion die head temperature (125, 140, 155 and
170°C) on the physical properties of the extruded pellets. All the blends were
preconditioned to 40% moisture content and then extruded using a single screw
extruder. The three zones of the barrel temperature profile (70, 90 and 100°C) and
screw speed (150 rpm) of the extruder were set constant throughout the extrusion
cooking process. The findings elucidated that changes of modified broken rice and
taro inclusion level and die head temperature had significant effects on water
stability and floatability of the pellets. Changing level of modified broken rice and
taro inclusion level from 15% to 25% increasd expansion ratio, floatability, and
reduces bulk density values. Similarly, as the die temperature was elevated, the
extruded pellets had higher expansion ratio, lower bulk density, higher floatability
values and better water stability. The pellets extruded using modified broken rice and
taro were very durable with fines produced at less than 1% for all treatments. Moreover, extruded pellets produced from 15% modified broken rice and taro
inclusion level and 170°C die head temperature had high floatability values which
were 100.00% and 93.33%, respectively. In conclusion, low inclusion of modified
broken rice and taro starch could be used to manufacture high quality floating pellets
with a very minimum optimization. |
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