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amylose occurs in trace amounts, i.e. from ca. 0% to ca. 4%.Under natural conditions, starch chains appear as left-handedspirals (helices) with six glucose residues per turn. Theprimary hydroxyl groups of glycoside residues are directedoutwards the helix, whereas the secondary ones and hydrogenbonds are pointed inwards. The outer side of the helixis hydrophilic and its inner tunnel – hydrophobic in character.Owing to this, different water-insoluble substances,including lipid compounds or iodine, may penetrate into thestarch helix, especially into amylose. The amylose-iodinecomplex is navy blue.The amylose chains and arranged in parallel amylopectinbranches (with a polymerisation degree of 10–30)form double helices with neighbouring chains which arestrengthened with hydrogen bonds. Six neighbouring left--handed double helices make up crystalline forms, of ca. 10nm in length [Eliasson & Gudmundsson, 1996]. At the siteswhere bunches (clusters) of double helices with an appropriate(over 10 glucoside residues) length appear, crystallineregions of starch are formed. In the areas wherebranches of amylopectin chains, its short chains or singlehelices of free amylose or amylose bound with lipid substancesoccur, either semi-crystalline or amorphous layersare likely to form. The crystalline layers formed fromrepeating subsequent amylopectin clusters together withamorphous substance present between crystals and crystallinelayers form spherical structures (“blocklets”),20–500 nm in size. The hard (crystalline) layers are composedof large “blocklets” (50–500 nm), whereas the soft(semi-crystalline) layers – of smaller ones (20–50 nm).Regions are arranged concentrically, the “hard” ones alternatelywith the “soft” ones [Kossman & Lloyd, 2000]. Starchcrystallinity, positively correlated with the content of amylopectinsand the number of double helices, ranges from15% to 45% depending on plant species [Eliasson &Gudmundsson, 1996].
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