  2001 AACC Annual Meeting Charlotte, North Carolina October 14-18, 2001 Charlotte Convention Center  |
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Method to study modification reactions of corn starch granules using reflectance confocal microscopy. J. A. GRAY and J. N. BeMiller. Purdue University, Whistler Center for Carbohydrate Research.
Methods to study granular reaction patterns of modified starch are desired. Recently, our lab developed a backscattered electron microscopy (EM) method to study anionic reactions in starch granules after conversion to thallium(I) salts (Huber and BeMiller, 2001). It would be useful to have a simpler method of locating reaction sites, i.e., one which avoids the lengthy sample preparation required for EM. The goal of this project was to develop such a method. Corn starch granules were modified with phosphoryl chloride at low levels. Anionic modified corn starch granules were exchanged with silver nitrate (0.1 M) and washed with 85% aqueous ethanol (65°C). Ethanol washing to remove excess silver nitrate was optimized by use of ICP-AES. Granules were viewed with confocal laser scanning microscopy (CLSM) in the reflectance mode after reduction with ascorbic acid (2% w/v). An advantage of reflectance CLSM over fluorescence CLSM is that photobleaching of sample is not a concern. To eliminate inherent reflectance of laser off granular edges or surfaces, granules were viewed in 20% sucrose solution. This method is being applied to study the effects of modification reaction conditions on the location of reaction sites within starch granules.
Copyright 2001
The American Association of Cereal Chemists