Study On Homogeneously Debranching Of Starch And Its Application As An Inclusion Carrier Of Functional Substances

Amylose is a linear polymer which is made up of α-D-glucose by α-1,4glycosidiclinkages. Under appropriate conditions, amylose undergoes a conformation change resultingin a single, left-handed helix that can complex ligand. As a carrier of a variety of ligands,amylose has been widely applied in several industries. In this study, the effect ofhomogeneously debranching of native starch on the inclusion complexation ablity of starchwas investigated and the species of debranched starch (amylose) which possessed the highestinclusion complexation capability was applied as an inclusion carrier of soybean lecithin andzinc ions. The effect of reaction parameters on the inclusion complexation effeciency ofsoybean lecithin and zinc ions was investigated. The structure and properties of theamylose/soybean lecithin and amylose/zinc inclusion complexes were studied. The mainresults were as follows:The effect of debranching time on the blue value of maize starch, cassava starch, potatostarch and waxy maize starch was investigated. The results showed that the inclusioncomplexation capability of starch was significantly improved after being debranched and thecomplexation capability increased with hydrolysis rate. The species of starch which possessedthe highest complexation capability after being completely debranched was potato starch, ofwhich the blue value was1.12. Therefore, debranched potato starch was selected as the carrierof functional substances.The effect of reaction parameters such as reaction temperature, reaction time andaddition amount of soybean lecithin solution on the soybean lecithin content and conversionrate was investigated. The results showed that the optimal conditions for preparingamylose/soybean lecithin complexes were: reaction temperature60℃, reaction time2h,addition amount of20wt.%soybean lecithin solution2g per gram of starch (dry basis). Thesoybean lecithin content and inclusion rate prepared under the optimal conditions were106mg/g and84.81%, respectively.The formation of amylose/soybean lecithin inclusion complexes was confirmed by theresults of XRD, FT-IR and DSC. The results of13C CP/MAS NMR suggested that theamylose/soybean lecithin inclusion complexes was formed by the hydrophobic interactionsbetween alkyl chain of soybean lecithin and helical cavity of amylose, with rest groups ofsoybean lecithin lie outside the helix cavity. The results of SAXS indicated that asemi-crystalline structure existed in the complexes, the complexes had a mass fractal structureand the molecules were arranged less tightly than that of the uncomplexed amylose. SEM results showed that the complexes displayed a rough appearance with thin crystals embeddedin the matrix. The results of degradability experiments showed that soybean lecithin wasmainly released in the small intestine. The results of stability experiments showed that thestability of soybean lecithin was improved after inclusion complexation with amylose.The effect of reaction parameters such as pH value, reaction temperature, reaction timeand addition amount of zinc chloride solution on the zinc content and conversion rate wasinvestigated. The results showed that the optimal conditions for preparing amylose/zinccomplexes were: pH value8.0, reaction temperature60℃, reaction time2h, addition amountof2mol/L zinc chloride solution1mL per gram of starch (dry basis). The zinc content andconversion rate prepared under the optimal conditions were128mg/g and82.05%,respectively.The formation of amylose/zinc inclusion complexes was confirmed by the results ofXRD, Raman and13C CP/MAS NMR. The results of XPS suggested that besides theinteractions between zinc ions and helical cavity of amylose, part of zinc ions were alsocoordinated to the O6, O2, O3, O4atoms of amylose by covalent bond. The results of SAXSindicated that a semi-crystalline structure existed in the complexes, the complexes had a massfractal structure and the molecules were arranged less tightly than that of the uncomplexedamylose. SEM results showed that the complexes displayed a bumpy appearance. The resultsof conductivity measurements showed that the electrical conductivity of the amylose/zinccomplexes was significantly lower than that of the physical mixtures, zinc element no longerexisted in the free form.