Effect of granular characteristics on the viscoelastic properties of composites of amylose and waxy starches
2008
Lu, T.J. | Duh, C.S. | Lin, J.H. | Chang, Y.H.
For elucidating the influence of granular properties on the viscoelastic characteristics of starch gel, in this study waxy corn and waxy rice starches pre-heated at different temperatures were mixed with amylose isolated from normal corn starch to form amylose-waxy starch composites. Rheological properties of the amylose, the waxy starches and the composites during aging at 25°C were determined and compared. Results showed that the storage modulus (G') of amylose solution (2%, w/w) during aging was lower than 48Pa, and the rheological properties during aging of waxy starches pre-heated at 60°C were too weak to be detected. The G' of waxy starches during aging decreased with increasing pre-heating temperature from 70 to 90°C, and the decrement on G' value was more obvious for waxy corn starch. The amylose-waxy starch composites had higher gel strength than that of amylose or waxy starch alone. The G' of amylose-waxy corn starch composite increased with increasing pre-heating temperature from 60 to 80°C and then decreased at 90°C, however, the G' of amylose-waxy rice starch composite increased with increasing pre-heating temperature from 60 to 90°C. Waxy corn starch had lower hot paste and final viscosities, but higher breakdown than waxy rice starch. Waxy corn starch also showed a rapid increase on the swelling power at temperature above 70°C, while waxy rice starch increased slowly. The rigidity and integrity of waxy corn starch granules was found lower than waxy rice starch at 90°C. Results indicate that granule properties and interaction occurred between amylose and starch granules play important roles during gelation of starch.
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