The effect of pH on hydrolysis, cross-linking and barrier properties of starch barriers containing citric acid
2013 (English)In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 98, no 2, 1505-1513 p.Article in journal (Refereed) Published
Green cross-linking of thermoplastic starch for food packaging applications has been intensely studied during the last decade as a method of producing water-insensitive renewable barriers. This work has shown how the barrier properties of paper coated with a barrier dispersion containing starch and citric acid were affected by the solution pH and the drying temperature. The barrier properties of the coated paper were linked to molecular properties showing both hydrolysis and cross-linking reaction of starch in the presence of citric acid at different solution pH and different reaction temperatures (curing) on cast films. Hydrolysis was shown to be almost completely hindered at solution pH ≥4 at curing temperatures ≤ 105 °C and at pH ≥ 5 at curing temperatures ≤150 °C, whereas cross-linking still occurred to some extent at pH ≤ 6.5 and drying temperatures as low as 70 °C. The water vapor transmission rate was significantly affected by the competition between these two reactions. Coated paper showed a minimum in water vapor transmission rate at pH was kept around 4 in the starch coating solution, corresponding to the point where hydrolysis was effectively hindered but where a significant degree of cross-linking still occurred.
Place, publisher, year, edition, pages
2013. Vol. 98, no 2, 1505-1513 p.
starch; cross-linking; hydrolysis; molecular structure; barrier properties; citric acid
IdentifiersURN: urn:nbn:se:kau:diva-27081DOI: 10.1016/j.carbpol.2013.07.040ISI: 000326313600034PubMedID: 24053833OAI: oai:DiVA.org:kau-27081DiVA: diva2:618316
ProjectsRenewable Functional Barriers