Influence of Pretreatment on Cold Water Solubility and Esterification Activity of Starch

The aim of this study is to improve the Cold Water Solubility (CWS) and esterification activity of Native corn Starch (NS) by pretreatment NS using NaOH/urea aqueous solution. The influence of pretreatment on granule shape and crystal structure of corn starch was investigated by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). It has been found that the average particle size of Pretreatment corn Starch (PS) decreased to nanometer level, smaller than those of NS (4-15 μm). XRD revealed that crystalline pattern of PS was VH-type, which was different from that of NS (A-type). The maximum CWS of PS was 96.77%, while the NS was only 0.3%. NS and PS were esterified with oleic acid catalyzed by lipase under the same conditions respectively. The effects of the pretreatment on esterification activity of the corn starches were investigated by analyzing the Degrees of Substitutions (DS) of the esterification products. The maximum DS of pretreatment starch oleate was 0.229, while the DS of native starch oleate was very low and even could not be detected.