微波处理对果胶构象的影响

本文主要通过测定特性粘度,结合尺寸排阻色谱-多角度激光散射联用法(SEC-MALLS)、动静态光散射法表征果胶构象,研究微波处理前后果胶的构象变化。结果显示,微波处理5、15、20、30 min,果胶的特性粘度从4.25 dL/g分别降低至3.35、3.10、2.97、2.85 dL/g。SEC-MALLS结果显示,微波处理30 min后,M_W由原果胶的31.38×10⁴ Da降低至4.76×10⁴ Da,表明微波处理会导致果胶的降解;通过对果胶溶液的R_g和M_W的双对数图α值进行分析,可以得出原果胶及微波处理5、15、20 min后果胶分子链构象为无规则线圈,而处理时间延长至30 min后,果胶分子的链构象变为刚性棒状。此结果与动静态光散射法表征得到的果胶构象变化一致。本论文为解释微波处理造成果胶理化性质变化提供一定的理论基础。

Effects of Microwave Treatment on Conformation of Pectin

In this study,the conformation changes of pectin induced by microwave treatment were determined by intrinsic viscosity,size exclusion chromatography combined with multi-angle laser scattering(SEC-MALLS),as well as dynamic/static light scattering. Results showed that,the intrinsic viscosity of pectin decreased from 4.25 dL/g to 3.35,3.10,2.97 and 2.85 dL/g after microwave treated for 5,15,20,30 min,respectively. The results of SEC-MALLS showed that M_W decreased from 31.38×104 Da to 4.76×104 Da after microwave treated for 30 min,indicating that microwave treatment could lead to degradation of pectin. By analyzing the α values of logarithmic diagram of R_g and M_W of pectin solution,it could be concluded that both origin pectin and microwave treated pectin for 5,15,20 min,the chain conformation of pectin was irregular coil. When the treatment time was extended to 30 min,the chain conformation of pectin molecules became rigid rods. This result was consistent with the conformation change of pectin characterized by dynamic and static light scattering method. This paper provided a theoretical basis for explaining the changes of physicochemical properties of pectin caused by microwave treatment.