Löfgren Caroline, Walkenström Pernilla, Hermansson Anne-Marie
SIK, The Swedish Institute for Food and Biotechnology, PO Box 5401, 402 29 Göteborg, Sweden.
Biomacromolecules. 2002 Nov-Dec;3(6):1144-53. doi: 10.1021/bm020044v.
The microstructure and the rheological properties of pure HM (high methoxyl) and LM (low methoxyl) pectin gels and of mixed HM/LM pectin gels have been investigated. Gel formation of either the HM or LM pectin, or both, was initiated in the mixed gels by varying the sucrose and Ca(2+) content. The microstructure was characterized by transmission electron microscopy, light microscopy, and confocal laser scanning microscopy. HM and LM pectin gels showed aggregated networks with large pores around 500 nm and network strands of similar character. Small differences could be found, such as a more inhomogeneous LM pectin network with shorter and more branched strands of flexible appearance. LM pectin also formed a weak gel in 60% sucrose in the absence of calcium. A highly inhomogeneous mixed gel structure was formed in the presence of 60% sucrose and Ca(2+) ions, which showed large synergistic effects in rheological properties. Its formation was explained by the behavior of the corresponding pure gels. In the presence of 60% sucrose alone, a homogeneous, fine-stranded mixed network was formed, which showed weak synergistic effects. It is suggested that LM pectin interacts with HM pectin during gel formation, thereby hindering secondary aggregation leading to the aggregated networks observed for the pure gels.
已对纯高甲氧基（HM）和低甲氧基（LM）果胶凝胶以及混合HM/LM果胶凝胶的微观结构和流变特性进行了研究。通过改变蔗糖和Ca(2+)含量，在混合凝胶中引发了HM或LM果胶或两者的凝胶形成。通过透射电子显微镜、光学显微镜和共聚焦激光扫描显微镜对微观结构进行了表征。HM和LM果胶凝胶显示出具有约500 nm大孔的聚集网络以及具有相似特征的网络链。可以发现一些细微差异，例如LM果胶网络更不均匀，链较短且分支更多，外观更灵活。在没有钙的情况下，LM果胶在60%蔗糖中也形成了弱凝胶。在60%蔗糖和Ca(2+)离子存在下形成了高度不均匀的混合凝胶结构，其在流变特性方面表现出很大的协同效应。通过相应纯凝胶的行为解释了其形成过程。仅在60%蔗糖存在下，形成了均匀的细链混合网络，其显示出较弱的协同效应。有人认为，LM果胶在凝胶形成过程中与HM果胶相互作用，从而阻碍了二级聚集，导致了纯凝胶中观察到的聚集网络。
