玉米淀粉的活化预处理及对其化学反应活性的影响

Activation of Corn Starch and Effect of the Activation on Its Reaction Activity

以氢氧化钠/尿素混合水溶液对玉米淀粉进行预处理使其活化,并采用SEM和XRD方法考察了活化对玉米淀粉颗粒形貌和结晶结构的影响。表征结果显示,活化后玉米淀粉颗粒变小,粒径为500nm左右;结晶度降低,晶型发生转变,由A型转变成VH型。以月桂酸和月桂酸甲酯为酯化试剂将原玉米淀粉及活化玉米淀粉在相同条件下进行酯化,通过考察酯化反应取代度的变化来研究活化对玉米淀粉化学反应活性的影响。实验结果表明,活化玉米淀粉与月桂酸甲酯反应的取代度显著提高,由0增加到0.3543,说明活化能有效提高玉米淀粉的化学反应活性。

Native corn starch（NS） was activated by pretreatment with NaOH/urea/H2O solution to improve its chemical reaction activity. Effects of the activation on granule shape and crystal structure of the corn starch were investigated by means of SEM and XRD. It was found that granule sizes of activated corn starch （AS） were about 500 nm, smaller than those of NS. XRD revealed that crystalline pattern of AS was VH type, different from that of NS. NS and AS were esterified separately with methyl laurate or lauric acid under the same conditions. Effects of the activation on reaction activities of the corn starches were investigated by annalyzing the influences of the activation on degrees of substitutions of the esterifications. The results indicated that when esterification reagent was methyl laurate, degree of substitution of AS was higher than that of NS, from 0 to 0. 354 3, which indicated that NaOH/urea activation enhanced chemical reaction activity of corn starch.