Starch Destructurisation in the Absence of Synthetic Polymers

In the patent literature, the terminology destructurised starch [46-65] refers to a form of TPS described as molecularly dispersed [57]. The destructurisation of starch is defined as melting and disordering of the molecular structure of the starch granules as a molecular dispersion [55, 56]. It means that, simultaneously, the native crystallinity of starch and its granular structure disappear. 

This is achieved by heating the starch above the Tg and the T of its components, until they undergo endothermic transitions under shear, temperature and pressure for a time sufficient to also destroy the granular structure. As already stated, the water volume fraction required has to be below 0.45 and preferably below 0.28 [27]. 

Following destructurisation, starch does not subsequently show its native crystallinity and loses its structure characterised by left-handed double helices, as reported above. 

Nevertheless, other forms of crystallinity, different from the native ones, induced by the interaction of the amylose component with specific molecules, can be observed. These types of crystallites are characterised by single helical structures and are known as V complexes [67]. 

The disappearance of the crystalline structure of the starch granule may be determined using conventional light microscopy techniques [67]. 

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