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KMID : 0380620090410040369
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Korean Journal of Food Science and Technology
2009 Volume.41 No. 4 p.369 ~ p.373
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Starch Liquefaction and Residence Time Distribution inTwin-Screw Extrusion of α-Starch
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Kim Sung-Uk
Lee Seong-Ju
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Abstract
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α-Waxy corn starch was used as a feed for twin-screw extrusion in order to enhance starch liquefaction withadded thermostable α-amylase (derived from Bacillus licheniformis). The residence time distribution and starch liquefactionwere investigated. The starch liquefaction was analyzed in terms of reducing sugar contents, molecular size from gelpermeation chromatography (GPC), and microstructure from scanning electron microscopy (SEM). The use of α-starchcontributed to the production of more reducing sugar than the use of raw starch use alone. From GPC, the effect of α-starch on the molecular size reduction was shown to be small. From SEM, irregular and damaged surface were observedon the extrudate from α-starch, as compared to those from raw starch. The spread of residence time distribution curveswas greater with feed of α-starch than raw starch, indicating that α-starch was hard to flow forward during extrusion. Thiscould be improved by increasing the feed moisture content and barrel temperature of extruder.
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KEYWORD
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twin-screw extrusion, starch liquefaction, α-starch, residence time distribution
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