Physicochemical properties of extrusion-modified konjac glucomannan |
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| Authors: | Orawan TatiratSanguansri Charoenrein William L Kerr |
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| Institution: | a Department of Food Science and Technology, Faculty of Agro-Industry, Kasetsart University, Bangkok, Thailand
b Department of Food Science and Technology, College of Agricultural and Environmental Science, University of Georgia, Athens, GA 30602 USA |
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| Abstract: | Konjac glucomannan was extruded and subsequently ground under four conditions denoted: KGM1 (33% solids, 90 °C), KGM2 (24% solids, 90 °C), KGM3 (24% solids, 90 °C, die restriction), and KGM4 (24% solids, 110 °C). SEM and particle size analysis showed that extruded KGM had slightly larger and rougher particles. The water absorption index was decreased to 47.92-128.80, as compared to 153.64 for the control (KGMC). The crystallinity index increased to 2.97 and 3.42 for KGM3 and KGM4 samples, as compared to 1.72 for the control. Zero-shear viscosity of 0.5% solutions decreased to 0.36-3.01 Pa s. All samples were shear-thinning and data were best fitted by the Cross model. Based on capillary viscometry, molecular weights were decreased to 2.7 × 105-9.9 × 105, as compared to 1.2 × 106 for the control. In most cases, properties were most altered by higher temperature and shear, and to a lesser extent by lower solids in the feed. |
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| Keywords: | Extrusion Konjac Glucomannan Water absorption Flow behavior |
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