Composition, structure and physicochemical properties of three coloured potato starches

Composition, structure and physicochemical properties of starch from red- and purple-fleshed potatoes were investigated and compared to those of typical yellow-fleshed potatoes. The starch from yellow has highest amylose (25.23%) content, following by purple (23.30%) and red (20.26%). The growth ring of the three starches differed, but granule morphology was largely similar. Each potato starch exhibited B-type crystalline patterns, with crystallinity ranging from 20.33% to 22.25%. The molecular weights and z-average radius of gyration exhibited significant difference among the three starch samples. The branch chain length distribution showed that purple potato starch had highest population of A chains and lowest population of B1 chains. Moreover, the pasting properties of the three samples differed remarkably. The purple (90.92%) and red (86.41%) potato starches presented extremely good light transmittance compared with the yellow potato starch (34.03%). Dynamic rheological analysis showed that all samples possessed a weak elastic gel-like structure.