pH对莲子淀粉糊化特性影响的研究

为探讨pH对莲子淀粉糊化特性的影响,研究采用快速黏度分析仪、流变仪和差示扫描量热仪,测定不同pH条件下莲子淀粉的糊化特性、流变特性和热力学特性,并进行不等温动力学分析。结果表明:莲子淀粉糊黏度随着pH的升高呈现先增大后减小的趋势,强酸性条件热稳定性较差,碱性条件下热稳定性较强。不同pH体系条件下的淀粉糊均为非牛顿流体,具有假塑性流体特征,pH不会改变淀粉糊的流体类型。通过Power law方程对其流变特性曲线进行拟合,各样本均为剪切稀化现象,所形成凝胶为弱凝胶,体系以黏性为主。在pH5时,莲子淀粉糊具有较明显的触变性。莲子淀粉的热焓值、峰值温度、终止温度、糊化温度随着pH的升高呈现出先增大后减小的趋势,在强酸条件下,淀粉发生酸化,糊化进程及回生进程变缓;由不等温动力学得出:pH5时为莲子淀粉糊化最佳酸碱度。研究结果为莲子淀粉的综合开发利用提供了一定的理论依据。

Effect of p H on Gelatinization Properties of Lotus Seed Starch

In order to investigate the effect of different pH values on the gelatinization properties of lotus seed starch,rapid viscosity analyzer,rheometer and differential scanning calorimeter were used to determine and compare the gelatinization,rheological and thermo dynamic properties of lotus seed starch under different pH conditions.The results showed that the viscosity of lotus seed starch pastry firstly increased and then decreased with the increase of pH value.The thermal stability of lotus seed starch pastry was stronger under alkaline condition than that under acidic condition.The starch pastes with different pH values were non-Newtonian fluids with pseudoplastic fluid characteristics.The fluid type of starch paste could not be changed under different pH conditions.The rheological properties of the starch paste could be well fitted by Power law equation.All samples were shear thinning,and the gel formed was weak gel,as well as the system was mainly viscous.The lotus seed starch paste at pH5 had obvious thixotropy.The thermal enthalpy value,peak temperature,termination temperature and gelatinization temperature of lotus seed starch firstly increased and then decreased with the increase of pH value.In strong acid system,the gelatinization and retrogradation of lotus seed starch paste became slow because starch was acidified.According to non-isothermal kinetics,pH5 was the great condition of gelatinization.The results can provide a certain theoretical basis for the comprehensive development and utilization of lotus seed starch.