Insights into network rearrangement of konjac glucomannan gel induced by post-gelation soaking

Abstract

Post-gelation soaking is a critical step in gel-based foods processing, which plays an important role in the physicochemical properties of konjac glucomannan (KGM) gels, and the related structural changes are yet less explored. Here we compared the gel network, KGM aggregates and molecular chemistry of pre-soaking (PS), hot water soaking (HWS), hot acid soaking (HAS) and cold acid soaking (CAS) gels. Our findings indicated that post-gelation soaking promoted the network rearrangement, resulting in greater elasticity and higher cross-linking density. The average pore size of the network of soaking gels was twice that of PS gel, and the fibril diameter of HWS, HAS and CAS gels increased to 46.86 ± 9.18 nm, 46.12 ± 11.76 nm and 38.99 ± 6.12 nm, respectively, contributing to the higher degree of anisotropy in gel network. Post-gelation soaking also favored molecular aggregation by increasing df and decreasing Rg of KGM aggregates. Molecular chemistry analysis suggested that the molecular structure of KGM remained unchanged, and the strengthened hydrogen bonds and hydrophobic interactions improved the compactness of aggregate structures. Moreover, heating accelerated the rearrangement of gel network, and the presence of acid enhanced its heterogeneity. These findings shed light on the structural changes that occur during post-gelation soaking, which can help to optimize the processing conditions of gel-based foods.