Abstract

Fatty acid esterification of starches is a well-known method for overcoming the water sensitivity of starch. This is desired for instance in starch-based materials for packaging etc, where the hydrophilic character of native starch limits the extent of use of such materials. An alternative way of producing water-resistent starch-based materials from modified starch is to perform the starch modification after the production of a starch- based material. In this study high-amylose potato starch films were prepared by casting from aqueous solution. High-amylose starch was chosen since amylose is known to be an excellent film forming component. The starch films were surface esterified with octanoyl chloride and pyridine using varying octanoyl chloride concentrations, temperatures and time. Measurements on the degree of substitution (DS) at the film surface, morphology, contact angle, esterification depth, water vapour transmission and water absorption were performed on the different modified films. The esterification reaction at the surface was initially very fast. A DS of approximately 2 was reached after only 15 minutes at 80 C, as shown by electron spectroscopy for chemcial analysis. The concentration of octanoyl chloride was found to be the most important parameter for a successful surface esterificiation. Temperature and time, however, seemed to be of little or no importance. Attenuated total reflectance FT/IR measurements of the films revealed that the depth at which the esterification took place was at least 1.1 μm. FT/IR transmission analysis through a tablet of the film showed that esterification was not taking place to a high degree in the bulk and was thus concentrated to the surface region. A significantly rougher film surface topography for the modified films compared to the unmmodfied films was revealed by electron scanning microscopy. Moreover, the surface energy was significantly lower for the modified than for the unmodified films and concomitantly water permeability through the films decreased almost linearly with the degree of surface octanoylation

Published in

Conference

XI International Starch Convention

SLU Authors

• Koch, Kristine

  • Department of Molecular Sciences, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Food Science
Environmental Sciences related to Agriculture and Land-use


Permanent link to this page (URI)

https://res.slu.se/id/publ/2222