Potato Starch

Potato starch is mainly stored as granular form inside the amyloplasts. Simply speaking, amylose of potato starch granules mainly exists as a regular amorphous structure, while amylopectin has a semi-crystalline structure. Potato starch granules could be classified into six levels of hierarchical structure. Level 1 structure is an individual chain that is constituted of ADP-glucose by α-(1→4)-glycosidic linkages. Chains with different lengths are connected through α-(1→6)-glycosidic linkages based on the branch number to form amylose and amylopectin molecules as a level 2 structure. Level 3 structure, cluster, was combined with the amylopectin molecule and intertwined with each other forming double helices. The branched cluster constructs the crystalline lamella, while helical cluster constructs the amorphous lamella with about a 9 nm interval. The thickness of crystalline lamella and amorphous lamella stands for the length of an amylopectin cluster. The amylose that existed in amorphous lamella was termed as level 4 structure. Level 5 structures are growth rings and concentric circles formed by the stacking of semi-crystalline shell and amorphous shell layer by layer, respectively. Three major populations of pore size distribution were found in potato starch, which are around 2.23–2.63 nm, 3.22–4.14 nm and 4.46–14.5 nm. Potato starch granules present sharper and more intense growing ring structures than cereal starches do, which may indicate that potato starch was less susceptible to mechanical damage.

Fig. 1 The multiple hierarchical structure (six level) of potato starch granule. (Tong C, et al. 2023)