Author
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Shogren, Randal |
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 7/22/2004 Publication Date: 10/28/2004 Citation: Shogren, R.L. 2004. Preparation, properties and non-food uses for starch esters of moderate degree of substitution [abstract]. Nordic Starch Network. p.9:33. Interpretive Summary: Technical Abstract: Although starch esters of moderate degree of substitution (DS) have been prepared previously and there are potential applications for these, they have not as yet become a commercial success. Part of the reason for this is that most syntheses have required expensive solvents or produced a large amount of byproduct. Here we report recent work on rapid, efficient modification of starch in acetic acid with little or no byproduct as well as characterization of some physical properties. Heated to more than 180 degrees C, native corn starch will melt in acetic acid accompanied by reduction in molecular weight and formation of amylose V-type complexes. These complexes are very stable, even to vacuum drying, but will dissolve to varying extents in water releasing acetic acid. Such complexes could have some uses as flavor or fragrance encapsulants. Starch gelatinized in acetic acid is very reactive to acetic, succinic and alkenylsuccinic anhydrides, with reaction efficiencies of 80-100% after heating at 150-170 degrees C for 3-8 min. Heating by microwave radiation seems to give somewhat more rapid acetylation than conventional conductive heating. Acetylation rates also increase with amylopectin content. Substitution occurs primarily (less than 70%) at the C6 position. The only byproduct of the reaction, acetic acid, can be rapidly removed by depressurization, leaving a white solid. Starch acetates are greater than 95% cold water soluble at DS values of 0.4-0.9 and reaction temperatures of greater than 160 degrees C. High amylose starch acetates form flexible films on drying and thus may be useful for applications such as textile sizes. Other applications contemplated include plasma expanders, pharmaceutical excipients, thickners and emulsifiers. Acetylation at lower (120 degrees C) temperatures gives starches of DS 0.2-0.5 which are water insoluble but highly swellable. These starches retain their native crystallinity, implying that the acetate substitution is a block pattern. Such water absorbing starches may have a variety of uses. Other types of starch esters as well as novel catalysts for esterification may also be described. |
