湿热处理淀粉的糊化特性及糊化机制

Study on the gelatinization behaviors of heat-moisture treated starch and its mechanism

以湿热处理淀粉为研究对象,采用动态流变仪(RHE)和差示扫描量热仪(DSC)在过量水分条件下[m淀粉∶m水=1∶10(g/g)]进行恒速和梯度升温糊化并研究其多阶段糊化特性和糊化机制。结果显示,湿热处理淀粉即使在过量水分条件下糊化也会呈现出双吸热峰(G和M1)和双黏度特征峰(PV1和PV2)。通过对热特性和黏度特性关联分析可将湿热处理淀粉糊化过程分为3个阶段:无定形区吸热(G)发生不可逆溶胀;晶体结构吸热(M1)解体快速吸水;结晶结构完全解体后体系自吸水溶胀(非吸热)。同时,湿热处理淀粉在糊化过程中具有时间和温度依赖特性,且淀粉在不同糊化阶段存在温度阈值,淀粉糊化的时间和温度依赖特性大小与温度阈值密切相关。

In this study,the gelatinization of heat-moisture treated(HMT)corn starch was investigated by rheometer(RHE)and differential scanning calorimeter(DSC)under the same condition of excessive water(starch∶water=1∶10)with heating-rate dependent gelatinization and time-temperature gradient gelatinization tests.DSC and RHE results showed that multiple endothermic transitions(G and M1)and two viscosity peaks(PV1 and PV2)were observed in viscosity curves and DSC traces even in excess water for HMT starches.The gelatinization process of HMT starch could be divided into three stages by correlation analysis of thermal and viscosity characteristics as follows.The first stage of swelling corresponded to the G endotherm,and the second stage of swelling corresponded to the M1 endotherm,followed by swelling non-corresponding to any endotherm.The temperature-dependent behaviors of corn starch gelatinization were evidenced by RHE results and starch gelatinization has different temperature thresholds at different stages.The degree of time-and temperature-dependence was closely related to these temperature thresholds.