Granules, starch disruption

The crystallinity of starch granules is disrupted during derivatization (Saroja et al., 2000), and this leads to a greater degree of separation between the outer branches of adjacent amylopectin... 

In its natural form, starch is not meltable and therefore caimot be processed as a thermoplastic. However, starch granules can be thermoplasticized through a gelatinization process. In this process, the granules are disrupted and the ordered crystalline structure is lost under the influence of plasticizers (e.g., water and glycerol), heat, and shear. The resultant melt-processable starch is often termed thermoplastic starch (TPS). Since the advent of TPS,... 

There are five prime factors that determine the properties of starches 1. starch is a polymer of glucose (dextrose) 2. the starch polymer is of two types linear and branched 3 the linear polymeric molecules can associate with each other giving insolubility in water 4. the polymeric molecules are organized and packed into granules which are insoluble in water and 5 disruption of the granule structure is required to render the starch polymer dispersible in water. The modification of starch takes into account these factors. 

In the 1940s, researchers identified that when starch is heated in water there were three distinct stages in the granule disruption process. During the first phase, water is slowly and reversibly absorbed by granules. 

Putaux, J. -L., Molina-Boisseau, S., Momaur, T., Dufresne, A. (2003). Platelet nanocrystals resulting from the disruption of waxy maize starch granules by acid hydrolysis. Biomacromol, 4,1198-1202. 

When starch is heated in excess water, the crystalline structure is disrupted (due to breakage of hydrogen bonds) and water molecules become linked by hydrogen bonding to the exposed hydroxyl groups of amylose and amylopectin. This causes an increase in granule swelling... 

Starch gelatinization is the disruption of molecular orderliness within the starch granule. It results in granular swelling, crystallite melting, loss of birefringence, viscosity development, and solubilization. 

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