Peculiarities of Cross-Linking Degree Determination for the Starches of Different Botanical Origin

摘要

Starches of different botanical origin, namely potato, wheat, and corn are cross-linked with epichlorohydrin (EPI) at cross-linking agent to starch molar ratios of 0.0005:1, 0.0017:1, 0.0055:1, and 0.01:1. The degree of cross-linking is evaluated by determining the solubility in aqueous 1 m KOH solution and assessing pasting properties of aqueous starch suspensions. It is found that the size of starch microgranules affects the degree of cross-linking and the smaller the granules are, the more cross-linking agent is required to achieve the same solubility or viscosity characteristics. The assessment of two methods reveals that solubility in alkali solution method can be used when determining the degree of cross-linking of starch in a wide range, meanwhile, a viscoamylography approach is only suitable when the amount of EPI in the modification reaction is increased to 0.01 mol per mole of starch. The peculiarities of both methods are discussed and may be useful when determining the degree of cross-linking of different starches with potential application as thickeners or sorbents.