STUDY OF 3-DIMENSIONAL STRUCTURE OF WHEAT-STARCH GRANULES STAINED WITH REMAZOLBRILLIANT BLUE-DYE AND EXTRACTED WITH AQUEOUS SODIUM DODECYL-SULFATE AND MERCAPTOETHANOL SOLUTION

Wheat starch granules were obtained from soft wheat flour by acetic ac id fractionation (pH 3.5), and the starch was stained by reaction with Remazolbrilliant blue (RBB) dye. RBB-stained starch was extracted wit h 1% sodium dodecyl sulfate (SDS) and 1% 2-mercaptoethanol (ME) for 14 .5 hr at room temperature. This extraction step was repeated five time s (extracts 1-5). SDS-ME extracts were subjected to size-exclusion col umn chromatography, and comparisons of their profiles for specific abs orbance at 650 nm (A(650)) and carbohydrates were made. After high mol ecular weight (HMW) carbohydrates on the starch granule surface were e xtracted, HMW carbohydrates inside the granule appeared to be extracte d. Finally, low molecular weight (LMW) carbohydrates near the granule surface were extracted. Phase-contrast tight microscopy of the treated starch granules showed that all granules became transparent. Two diff erent interior structures were observed. Scanning electron microscopy indicated that the granule was split into two parts at the equatorial groove. The interior of the granule showed two different areas: a cent ral hole area and the surrounding stratified area. Extraction beyond f ive times with the same solvent dissolved the weak part of the granule structure and left two types of skeletal structures. The appearance o f the skeletal structure of the granule surface was different from the appearance of interior structures.