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Study of Internal Structure of Waxy Wheat Starch Granules by KI/I₂ Solution

¹Faculty Home Economics, Laboratory of Food Technology, Kobe Women's University, Suma-Ku, Kobe City, Japan 614. ²National Agriculture Research Center (NARC), MAFF, Tsukuba-Shi Ibaraki, Japan 305. ³Kobe Women's Junior College, Kobe City, Japan 650. ⁴Toyama Prefectural Food Research Institute, Toyama, Japan 939.

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/I₂ solution. Subsequently, the concentration of the KI/I₂ solution was increased to >2.5% KI and 1.0% I₂. Then the appearance of the waxy wheat starch granules quickly became ghostlike. 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 × 10⁵ and 23.8 × 10⁶ from Berry plots, respectively.