Molecular Characterizing of Starch and Starch Based Materials in Food Packaging

Starch is a promising polymer as a renewable alternative to petroleum and nature gases. However, native starch possesses limitations such as low shear stress resistance, thermal decomposition, high re-crystallisation/retrogradation, and syneresis. Acid hydrolysis followed by acetylation is a reaction used to improve the film-formation of native starch. Acetylation foremost improves the hydrophobicity of starches. In addition, acetylated starches have shown to form films more easily compared to unacetylated starches. Controlling different modifications of starches can help tailoring mechanical and barrier properties of materials, therefore improving the effectiveness of food packaging. The object of this investigation was to examine how the structure of certain starches was affected by chemical modifications as acid hydrolysis and acetylating as well as by film-forming. The ratio of amylose and amylopectin was examined by using size exclusion chromatography (SEC), followed by phenol-sulfuric acid reagent and iodine-staining. Secondly, High Performance Anion Exchange Chromatography with Pulsed Amperometric Detection (HPAEC-PAD) was used to determine the amylopectin chain length distribution. In acid hydrolyzed starches, the amylopectin and amylose content was replaced to a great extent by degradation products yield by the depolymerizing reaction of acid hydrolysis. Acetylation was found to have a smaller degrading effect as well. However, film forming performed by solution casting did not seem to contribute to any further degradation of the polymers. Starches with a great extent of degradation possessed an increased amount of chains with degree of polymerization (DP) values between 35-65 due to degradation of the highly branched amylopectin molecule.