Study of internal structure of waxy wheat starch granules by KI/I2 solution

Wheat starch granules were separated from waxy wheat flour by the acetic acid (pH 3.5) fractionation technique. Waxy wheat starch samples were stained red-brown using KI/I-2 solution. Subsequently, the concentration of the KI/I-2 solution was increased to >2.5% KI and 1.0% I-2. Then the appearance of the waxy wheat starch granules quickly became ghost-like. The internal structure of the ghost could be observed. This structure consisted of two parts with different colors: a red-brown central part and a slightly pinkish surrounding part. Sonication of the ghost at 20 kHz for 20 sec separated the central part from the surrounding part. Each of the separated parts were subjected to gel-filtration chromatography, and their chromatography profiles indicated only amylopectin and no amylose. The central and surrounding parts had molecular weights of 54.3 x 10(5) and 23.8 x 10(6) from Berry plots, respectively.