Solution properites of dialdehyde starch

Abstract

AbstractLow levels of periodate oxidation increased the dispersibility of cornstarch in water at 98°C. Above the 10% level of oxidation, cornstarch became more resistant, and longer heating times were generally required to form stable solutions. Light‐scattering, sedimentation, and viscosity measurements showed that the average particle weight in solutions of periodate‐oxidized starches generally decreased with increased level of oxidation and time of heating. Introduction of dialdehyde groups into the anhydroglucose residues of the starch molecules thus made the structure labile toward degradation on heating in water. The experimental results showed, however, that an aggregation reaction also occurred in solutions of oxidized starches. This reaction was most evident at 10% oxidation level, but it was found to occur simultaneously with degradation over a range of oxidation levels. Aggregation probably results from the reaction of aldehyde groups of one molecule with hydroxyl groups of neighboring molecules. The observation that aggregation could be prevented by additon of glucose was explained by competition of hydroxyl groups of glucose with hydroxyl groups of starch in their reaction with aldehyde groups. The angular dependence of the light‐scattering measurements indicated that formation of dumbbell‐shaped particles by crosslinking of near‐spherical particles was probably quite important to the aggregation reaction. Preliminary investigation of periodate‐oxidized waxy maize starch showed that this starch had a much lower average molecular weight in solution than ordinary cornstarch at a comparable level of oxidation. This value may result from the contribution of amylose to the aggregation of ordinary oxystarch.