制备过程中淀粉浓度对莲子回生淀粉理化特性的影响

本文从热稳定性、膨胀度及溶解度、黏度、流变特性等方面研究制备过程中淀粉浓度对莲子回生淀粉(Retrograded starch,RS)理化特性的影响。热重分析(Thermogravimetric analysis,TGA)结果表明,5%及40%淀粉浓度下的回生淀粉含有较多易挥发物质,20%淀粉浓度下的回生淀粉含有较多相对热稳定组分。随着淀粉浓度增加,莲子回生淀粉膨胀度减小,溶解度增大,黏度递减,且样品膨胀度及溶解度随温度升高而增加。由静态流变结果可知,所有样品均表现出剪切稀化特性,且5%、10%及20%淀粉浓度下的回生淀粉的黏度高于30%、40%及50%淀粉浓度下的回生淀粉的黏度;由动态流变结果可知,当角频率小于10 rad·s^-1时,所有样品的储存模量均不受角频率影响;当角频率大于10 rad·s^-1时,5%、10%及20%淀粉浓度下的回生淀粉的储存模量随角频率增加而减小,而30%、40%及50%淀粉浓度下的回生淀粉的储存模量随角频率增加而增大;所有样品的损失模量均随角频率升高呈上升趋势。综上,莲子淀粉回生行为受到回生过程中淀粉浓度的影响,并在理化性质上呈现差异。

Effect of Preparation Concentration on the Physicochemical Properties of Retrograded Starch from Lotus Seed

The effect of preparation concentration on the physicochemical properties of retrograded starch(RS)from lotus seed was investigated. The thermal stability,swelling power and solubility,viscosity,rheological properties of samples were determined,respectively. Thermogravimetric analysis(TGA)showed that RS5% and RS40% of contained more volatile substances,while RS20% contained more relatively stable heat-stable components among samples. As the starch concentration increases,the swelling powers of all samples reduced,and the solubility increased,as well as the viscosity decreased. Moreover,the swelling power and solubility increased with the increasing temperature. It could be seen from the static rheological results that all samples exhibited shear thinning characteristics,and the viscosities of RS5%,RS10%,and RS20% were higher than those of RS30%,RS40%,and RS50%. Furthermore,from the results of dynamic rheology,when the angular frequency was less than 10 rad·s-1,the storage modulus of all samples was not affected by the angular frequency. when the angular frequency was greater than 10 rad·s-1,the storage modulus of RS5%,RS10%,and RS20% decreased with the increasing angular frequency,whereas the storage modulus of RS30%,RS40%,and RS50% increased with the increasing angular frequency. The loss modulus of all samples increased with the increasing angular frequency. All in all,the preparation concentration of starch displayed a significant effect on the physicochemical properties of retrograded starch from lotus seed. The physicochemical properties of retrograded starch with low concentrations of starch(5%,10%,20%)had a significantly different compared to retrograded starch with high concentrations(30%,40%,50%).