Internal structure of normal maize starch granules revealed by chemical surface gelatinization.
Normal maize starch was fractionated into two sizes: large granules with diameters more than 5 microns and small granules with diameters less than 5 microns. The large granules were surface gelatinized by treating them with an aqueous LiCl solution (13 M) at 22-23 degrees C. Surface-gelatinized remaining granules were obtained by mechanical blending, and gelatinized surface starch was obtained by grinding with a mortar and a pestle. Starches of different granular sizes and radial locations, obtained after different degrees of surface gelatinization, were subjected to scanning electron microscopy, iodine potentiometric titration, gel-permeation chromatography, and amylopectin branch chain length analysis. Results showed that the remaining granules had a rough surface with a lamella structure. Amylose was more concentrated at the periphery than at the core of the granule. Amylopectin had longer long B-chains at the core than at the periphery of the granule. Greater proportions of the long B-chains were present at the core than at the periphery of the granule.
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Department of Food Science and Human Nutrition, Iowa State University, Ames, Iowa 50011, USA.
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D000687:Amylopectin / Q000737:chemistry; D000688:Amylose / Q000737:chemistry; D002122:Calcium Chloride; D005782:Gels; D018021:Lithium Chloride; D008855:Microscopy, Electron, Scanning; D008970:Molecular Weight; D010316:Particle Size; D013213:Starch / Q000737:chemistry*; D013499:Surface Properties; D003313:Zea mays / Q000737:chemistry*
D005782:Gels; D013213:Starch; D000688:Amylose; D000687:Amylopectin; D018021:Lithium Chloride; D002122:Calcium Chloride