The solid state and nanostructure of starch: Effects on starch functionality

In order to determine suitable end use applications for different starches, this review characterizes and differentiates the physical components, solid state, crystalline structures, and their effects on gelatinization, retrogradation, texture and functionality. There exist four crystalline packings of starch. A-, B- and C-type packings are attributed to amylopectin, and V-type which is attributed to amylose. B- and C- type crystallinity rely on water to help coordinate their crystal structures due to the congregation of water in the large intrahelical cavity of the B-type packings. The ratio of amylose to amylopectin content largely affects the textural and functional properties of starch. Amylose largely influences retrogradation, and thus can largely impact the crystallinity, strength, cohesion and brittleness of starch gel systems. Amylose has been found to crystallize prior to amylopectin, suggesting that amylose acts as a nucleation site for further radial crystallization of amylopectin. Processing treatments such as size reduction and drying, which are typically applied to all commercial starches, also impact the physiochemical and functional characteristics of the starch. These processes can cause damage to the starch granule while reducing crystallinity in the native starch, but also increasing retrogradation in gelatinized systems.