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vol.17 issue3Surface Morphology of Sour Cassava and Native Potato Thermoplastic Starches by Optical and Atomic Force MicroscopySimulation of Free Radical Polymerization in the Entire Conversion Range author indexsubject indexarticles search
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Información tecnológica

On-line version ISSN 0718-0764

Abstract

ACOSTA, Harold A; VILLADA, Héctor S  and  PRIETO, Pedro A. Ageing of Sour Cassava and Native Potato Thermoplastic Starches by Atomic Force Microscopy. Inf. tecnol. [online]. 2006, vol.17, n.3, pp.71-78. ISSN 0718-0764.  http://dx.doi.org/10.4067/S0718-07642006000300011.

This study reports on the topography of thermoplastic starches (TPS) from sour cassava and native potato using atomic force microscopy (AFM), over a 120 day-storage period. Mixtures of sour cassava (fermented) and native potato starches plus glycerine, were processed using a single-screw extruder. Sour cassava thermoplastic starch (SCTPS) and native potato thermoplastic starch (NPTPS) films were observed and measured by AFM (in contact mode). Their surfaces showed increased rugosity, and smooth parts only at high plasticizer content. However, SCTPS always had lower rugosity than NPTPS, due to the natural fermentation of sour cassava starch. These changes were related to starch granule size and shape, and particularly to plasticizer content. NPTPS with higher rugosity presented phase separation at 120 days, due to retrogradation of starch molecules which tended to form crystallites. These findings indicated that sour cassava starch can lower TPS retrogradation which is important in the development of biodegradable packaging.

Keywords : thermoplastic starches; atomic microscopy; rugosity; topography.

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