The Challenges of Analyzing the Molecular Properties of Starch
Sammanfattning: Both the nutritional and functional properties of starch are directly influenced by the molecular structure of its polymers: amylose and amylopectin. It is therefore important to have reproducible methods for quantifying the molecular size. In the first part of the thesis, the composition, crystallinity, degree of branching, morphological, thermal and pasting properties, and susceptibility of the granules to enzymatic hydrolysis of starches from Lepidium meyenii, Chenopodium quinoa, Chenopodium pallidicaule, Amaranthus caudatus and Canna indica, Xanthosoma sagittifolium and Manihot esculenta, grown in Bolivia, were investigated. The physicochemical properties of the starches varied depending on its botanical source. Some starches exhibited very unusual properties. The second part of this study deals with the development and evaluation of starch dissolution methods allowing reliable measurements of the size distributions of starch polymers using asymmetrical flow field-flow fractionation coupled to multi-angle light scattering and refractive index detection (AF4-MALS-dRI). Three of the most common methods for starch dissolution were investigated, i.e. dissolution in water at high temperatures (120°C – 200°C) using autoclaving or microwaving heating, and dissolution in DMSO at 100°C. The results showed that autoclaving aqueous solutions at 140°C and dissolution in DMSO at 100°C were suitable methods for dissolving amylopectin, whereas dissolution in DMSO was the optimum method for dissolving amylose.
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