Characterisation of starch: development of analytical methods

Abstract: Starch, comprised of amylose and amylopectin, is a very complex biopolymer. Different methods are therefore needed for the investigation of the molecular structures of amylose and amylopectin. In this thesis analytical methods have been developed and various techniques were combined for the characterisation of starch. Microdialysis was used for sampling and sample clean-up coupled on-line with anion-exchange chromatography for the determination of starch hydrolysis products. Both enzyme-based hydrolysis of native and modified starch and enzyme-based detection systems were studied. The enzymes were used either in solution or immobilised in enzyme reactors or in a biosensor format. Molecular parameters for native starch, amylose and amylopectin were determined such as the degree of branching, blue-value, chain length distribution, and b-limit value. The substitution patterns of modified starch derivatised under homogenous or heterogeneous conditions were determined. Key-criteria in the development of analytical methods are selectivity, sensitivity, repeatability, accuracy, limit of detection, simplicity, total analysis time, and automatisation. The last three criteria were addressed by using on-line and flow injection techniques. Selectivity was obtained by applying enzyme-based methods. The variations in the results obtained with various methods were discussed in the summary of the eight papers included in this thesis.