2001 AACC Annual Meeting Charlotte, North Carolina October 14-18, 2001 Charlotte Convention Center

The influence of both the degree of substitution and the distribution of substituents in starch on the gelatinization behavior was studied for the particular case of acetylated waxy corn starch. The location of amylopectin substituents in starches with acetylating degrees ranging from 0 to 6.5% was monitored by chromatographic analysis of the dextrins remaining after both beta-amylolysis and degradation with alfa-amylase and subsequently amyloglucosidase. The results clearly confirmed that the acetyl groups are predominantly situated near the amylopectin branching points. Solid state (^13)C CP/MAS NMR revealed only a small broadening of the C-1 signal as a result of acetylation, indicating only minor changes in the double helix content of the starches. Wide and small angle X-ray scattering on the other hand showed that crystalline as well as lamellar order within the granule was gradually lost on acetylating. Thermal analysis in limited water conditions showed the appearance of a gelatinization and melting endotherm with decreasing peak temperatures and enthalpies upon increasing degree of substitution. In addition, higher degrees of acetylation increased the relative importance of the melting endotherm. These observations will be discussed in view of the side-chain liquid-crystalline polymer behavior of amylopectin.