Side-chain liquid-crystalline model for starch

A chiral side-chain liquid-crystalline polymeric model for the structure and physical properties of starch was reviewed and extended [1-6]. The lamellae in starch are considered in terms of three components: backbone, side-chains and double helices. It is the degree of mobility of these three components, coupled with the helix-coil transition, which gives starch its distinctive properties. The model is used to help explain phenomena involved during hydration, gelatinisation, plasticisation, freezing, and morphogenesis. The new technique of scanning microfocus X-ray diffraction is used to study double helix orientation and the tilt of the lamellae. Using integration of the double helix orientation along closed contours in single potato granules it is shown that they conain a "+1" hedgehog disclination. The effect of the chirality of the double helices on the phase behaviour is highlighted.