Preparation and characterization of konjac glucomannan and gum arabic composite gel

Abstract

Compounding is a safe method to avoid limitations of a singular gel. Here, composite gels were prepared with konjac glucomannan (KGM) and gum arabic (GA) and evaluated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), water solubility index (WSI), water absorption index (WAI), texture profile analysis (TPA) and rheological analysis. The gel stratified when GA concentration ≥ 2.5%. FTIR indicated that the interactions of KGM and GA were mainly related to hydrogen bonds and acetyl groups, and the solution separated from gels only included GA and water molecules. The microstructures became denser and contained smaller holes at high GA concentrations as seen by SEM. WSI and WAI both increased with GA increasing. Hardness and springiness dropped when GA concentration increased from 0 to 2.0%, but they increased when GA increased from 2.0% to 4.0%. Rheological analysis showed the gels were non-Newtonian pseudoplastic fluids, with anti-thixotropy (GA ≤ 3.5%) and thixotropy (GA ≥ 4.0%). Furthermore, the gels could be classified as non-covalent gels, with higher gel strength at high GA concentrations. The non-covalent linkages included hydrogen bonding and hydrophobic interaction, and hydrogen bonding held the dominated status. Therefore, KGM and GA have antagonistic and synergistic effects.

Keywords: Gum arabic; Hydrocolloids; Konjac glucomannan.