Effect Of Counter-Rotating Twin Screw Extruder On The Physicochemical And Functional Properties Of Sago (Metroxylon Sagu) Starch

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dc.contributor.authorAisah Bujang
dc.date.accessioned2022-11-01T01:31:38Z
dc.date.available2022-11-01T01:31:38Z
dc.date.issued2007-03
dc.description.abstractThis 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 (3􁪽, 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. The destruction of starch granular structure was evident by the increase of water solubility capability up to 72.26% and decrease in water absorption capacity (4.37 gIg). The destruction was also observed in the changes of pasting behaviour. Partial loss of crystallinity observed from x-ray diffractograms showed shifting of native sago starch x-ray pattern form C-type to Btype for extruded sago starch. Formation of amylose-lipid complex was induced by availability of amylose released due to melting of granular crystallinity which is facilitates by extrusion at high shearing rate. Reduction in the intensity stretching of glycosidic C-C starch bond linkages, increase intensity of OH groups stretching and formations of a and 13 anomers as showed by FTIR spectra have qualitatively suggested that higher level of destructions have occurred. Maximum degree hydrolysis of 86.77% obtained showed improvement on the in-vitro digestibility of extruded sago starch compared to the native sago starch (63.25%) after 12 hours of incubation at gODe with thermostable a-amylase. Reduction in intrinsic viscosity from 127.62% for native sago starch to 40.35% for sago extrudate (100rpm screw speed. 30% w/w db moisture content) suggested that reduction of starch molecular weight with more linear starch chains was released.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/16502
dc.language.isoenen_US
dc.publisherUniversiti Sains Malaysiaen_US
dc.subjectTechnologyen_US
dc.titleEffect Of Counter-Rotating Twin Screw Extruder On The Physicochemical And Functional Properties Of Sago (Metroxylon Sagu) Starchen_US
dc.typeThesisen_US
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