基于快速黏度仪及流变仪的大米米糊流变特性的研究

Study on the rheological properties of rice paste with RVA and rheometer

本文应用快速黏度仪-旋转流变仪对3种大米(粳米、籼米及糯米)及不同糯米米糊的流变特性进行了研究,分别从稳态流动实验、频率扫描及粘弹性温度扫描进行考察。结果表明:大米米糊表现出明显的剪切稀化现象,粳米与籼米相比糯米而言越易出现剪切稀化;对于零剪切黏度,表现出粳米>籼米>糯米,对于黏度,粳米与籼米虽高于糯米,但差异已明显减小,而粳米与籼米之间相近;不同糯米之间在零剪切黏度及黏度上存在差异性。频率扫描表明米糊的弹性行为大于黏性行为,动态黏度随频率增加出现明显下降;粳米与籼米的弹性模量明显大于糯米,损耗正切值明显低于糯米,不同糯米之间在弹性模及损耗正切上亦存在差异性。储存过程中,大米米糊零剪切黏度、黏度及弹性模量均出现下降。黏弹性温度扫描中,通过每天的弹性模量值与初始弹性模量值之间进行相对偏差值的计算,可评价淀粉是否发生明显老化。随着温度的升高,弹性模量、黏性模量及动态黏度出现持续下降,而损耗正切即黏弹性比值却逐步增加。

In this paper,the rheological properties of rice paste concerning 3 kinds of rice( japonica rice,indica rice and glutinous rice) and different glutinous rice were studied using RVA and rheometer from the experiments including steady flow,frequency sweep and viscoelastic temperature sweep. The results show that for rice paste there exists obvious shear thinning phenomenon and compared to glutinous rice,japonica and indica rice are more prone to shear thinning. As for zero-shearing viscosity it shows japonica > indica > glutinous. While for viscosity,japonica and indica rice which are close are higher than glutinous rice,but the difference is significantly reduced. Among different glutinous rice,there exist differences on zero-shearing viscosity and viscosity. In the frequency sweep,it shows for the rice paste the elastic behavior is greater than the viscous behavior,and the dynamic viscosity decreases obviously with the increase of frequency. For the japonica and indica rice,G'is significantly greater than that of glutinous rice while the value of loss tangent is obviously lower. There also exist differences on the G'and tan( delta) between different glutinous rice. In the storage process,zero-shearing viscosity,viscosity and G'of the rice paste decrease. In the viscoelastic temperature sweep,the relative deviation between G'on everyday and initial G'is calculated,as can be used to evaluate whether the obvious resuscitation of starch occurs. As the rise of temperature,G',G″ and η * continues to decline while the tan( delta)namely viscoelastic ratio gradually increases.