淀粉糊老化行为的粒子示踪微流变表征方法初探

Preliminary investigation of a novel method for revealing retrogradation behavior of starch paste by particle tracking microrheology

为在不接触和破坏样品的情况下对淀粉糊流变行为进行表征,实现同一样品在不同老化时间的连续测定,该研究利用被动粒子示踪微流变(passive particle tracking microrheology,pptMR)连续表征淀粉糊在冷却及冷藏老化过程的流变及内部结构变化情况。研究发现,pptMR所给的弹性因子(elasticity index,EI)、流度因子(fluidity index,FI)和固液平衡值(solid-liquid balance,SLB)能很好地表征直链淀粉短期老化,相比之下,SLB区分度最好。宏观黏度因子(macroscopic viscosity index,MVI)能同时表征直链淀粉短期老化与支链淀粉长期老化。pptMR能通过弹性模量(G′)、损耗模量(G″)和损耗角正切(tanδ)反映淀粉糊冷却过程黏弹特性连续变化及凝胶转变点,也可对其长期老化进行表征。pptMR是一种潜在的淀粉老化行为连续表征方法,具有机械流变学无法比拟的优势,但需深入研究。

In order to characterize the rheological nature of a starch paste in a non-contacting and non-destructive way along with its aging, passive particle tracking microrheology (pptMR) was used to evaluate rheological properties and inner structure of starch past during cooling and refrigeration. The results showed that pptMR derived elasticity index (EI), fluidity index (FI) and solid-liquid balance (SLB) could well characterize short-term retrogradation of amylose. In particular, SLB presented a higher resolution. On the other hand, macroscopic viscosity index (MVI) was effective to reflect short-term retrogradation of amylose and also long-term retrogradation of amylopectin. Moreover, pptMR derived elastic modulus ( G ′), loss modulus ( G ″) and loss tangent (tanδ) were good indicators of continuous changes in viscoelastic nature and sol-gel transition of starch paste upon cooling, which could also characterize long-term retrogradation of starch paste. In summary, pptMR is a potential method for continuously exploring cooling-induced aging events of starch paste, which has undoubtable advantages comparing against traditional mechanical rheology with further methodological investigation should be addressed in the future.