甘薯淀粉糊的流变特性

通过考察甘薯淀粉糊在不同甘薯淀粉浓度和不同温度下的流变特性,结果表明甘薯淀粉糊是典型的非牛顿型、剪切变稀的和触变性流体,温度越高,浓度越低,甘薯淀粉糊的滞后性越小;同时用幂律方程和Cross方程来描述糊的流变特性,发现Cross方程比幂律方程拟合精度更高。而浓度很低的情况下(如2%),甘薯淀粉糊的触变特性与其他浓度不同,表现为下行线在上行线之上,更适合用Herschel-Bulkley方程来描述它的流变行为。甘薯淀粉糊的动态流变行为则表现为在将开始糊化时,储能模量G’、损耗模量G"和tanδ都急剧上升,在到达糊化顶峰时急剧下降,而在降温过程中G’和G"都呈上升趋势,tanδ则是在100～50℃时下降,50～20℃时上升。

Rheological Properties of Sweet Potato Starch Paste

The rheological behaviours of sweet potato starch paste at various concentrations (2%, 5%, 8%, 10% and 20%) and at various temperatures (20℃, 40℃, 60℃ and 80℃) were assayed respectively. The results showed that sweet potato starch paste is a typic non-Newtonian, shear-thinning and thixotropic fluid, whereas the higher the temperature or the lower the concentration, the smaller the hysteresis loopis. The rheological behaviours of sweet potato starch paste are explained better by Cross equation than Power Law equation. Variations of viscosity of Sweet potato starch paste temperature ramp from 20℃ to 90℃ at shear rate of 10s-1 and 100s-1 were also investigated respectively. The results showed that sweet potato starch paste is tempersture-sensitive and suitable for Arrhenius equation. Sweet potato starch paste with low concentration (e.g. 2%), however, exhibits an unique behaviour that the Downlink was above the Uplink, described using Herschel-Bulkley equation. The results exhibits an unique behaviour that the Downlink is above the Uplink, using Herschel-Bulkley equation. The results by dynamic rheological measurement showed that the storage modulus (G’), loss modulus (G") and loss factor(tanδ) of sweet potato starch paste increase sharply from initial gelatinization temperature(ToG’) to maximal gelatinization temperature(TG’max) and decrease sharply over TG’max, that the storage modulus (G’) and loss modulus (G") of sweet potato starch paste increase during cooling, while loss factor(tanδ) decreases during 100～50℃ and increased during 50～20℃.