Effect of degree of deacetylation on physicochemical and gelation properties of konjac glucomannan

Abstract

Gelation behaviors of konjac glucomannan (KGM) samples with different degree of deacetylation (DD) obtained using a heterogeneous deacetylation method were studied by dynamic viscoelastic measurements in order to probe the role of acetyl groups in the gelation process of KGM and types of molecular forces responsible for gel formation. Molecular parameters and structure of KGM samples were determined by GPC–MALLS and FT-IR spectroscopy. It was found that water solubility of KGM decreased with increasing DD, providing evidence further that the presence of acetyl groups confers water solubility on KGM. Rheological measurements suggested that hydrogen bonding and hydrophobic interaction are both presented in KGM gels, hydrophobic interaction was strengthened whilst hydrogen bonding was weakened with increasing DD. A faster gelation rate and a more elastic modulus were facilitated by raising temperature or increasing KGM sample concentration. The conditions under which gelation can occur became easier with increasing DD.