Bujang, Aisah
(2007)
Effect Of Counter-Rotating Twin Screw Extruder
On The Physicochemical And Functional Properties
Of Sago (Metroxylon Sagu) Starch.
PhD thesis, Perpustakaan Hamzah Sendut.
Abstract
This research project was conducted to study the extent of destruction of sago starch
(Metroxylon sagu) by using counter-rotating twin-screw extruder. The effect of primary
extrusion parameters, screw speed (100, 125, 150, 175 and 200 rpm) and moisture
content (30, 40, 50 and 60% w/w dry basis) was evaluated with barrel temperature
kept constant. The changes in both physicochemical and functional properties
induced by extrusion processing were studied. High shear forces of the counterrotating
twin screw have been suggested in this study to caused not only granular destruction but also destructions at the molecular level. Initial granular structural
destruction was observed on the physical structures of the extrudates obtained.
Maximum expansion ratio of 7.83 was obtained at 125 rpm screw speed and 30% w/w
db moisture content, with lowest bulk density of 0.128 g/cm3 and minimum breaking
strength of 0.548 Nm2• Cross section of the extrudate by SEM micrographs also showed highly porous structures with polyhedral gas cells formed. Swelling capability,
shape of the gas cells and smoothness of the inner gas cells surface points out that
starch granules breakdown have occurred.
Actions (login required)
 |
View Item |
