Abstract

The effect of citric acid (CA) on starch films has been examined. A new method to detect cross-linking of starch by CA in solution-cast films by molecular weight measurements is described. Furthermore, we managed to distinguished between free, mono- and di-esterified CA and quantify di-ester content within starch films by using a modification in the method of complexometric titration with copper(II)-sulfate. Cross-linking of starch by CA occurred at low temperature, 70 ◦ C, which we assumed is so far the lowest temperature reported where cross-linking reaction occurred. This is essential for starch coating applica- tions within paper industry since no high temperatures for curing will be required. However, curing at 150◦C and high CA concentrations, 30pph, increased cross-linking reaction. Furthermore, the physical properties like water solubility, gel content and glass transition temperature, were highly reflected by changes in the molecular structure i.e. cross-linking and hydrolysis, as well as CA content and curing temperature.

Keywords

Starch-based film, Citric acid, Cross-linking, Molecular weight, Hydrolysis, Amorphous starch, Plasticization

Published in

Carbohydrate Polymers
2013, Volume: 96, number: 1, pages: 270-276

SLU Authors

• Menzel, Carolin

  • Department of Molecular Sciences, Swedish University of Agricultural Sciences
    

• Andersson, Roger

  • Department of Molecular Sciences, Swedish University of Agricultural Sciences
    

• Kuktaite, Ramune

  • Department of Biosystems and Technology, Swedish University of Agricultural Sciences
    

• Koch, Kristine

  • Department of Molecular Sciences, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Materials Chemistry
Polymer Chemistry
Food Science


Publication identifier

DOI: https://doi.org/10.1016/j.carbpol.2013.03.044

Permanent link to this page (URI)

https://res.slu.se/id/publ/41794