Rheological properties of extracted malva nut gum (Scaphium scaphigerum) in different conditions of solvent

Mucilage of malva nut fruit has been used as traditional medicine in Thailand. Health benefits of this mucilage are linked to its gelling property. This research was aimed to evaluate oscillatory rheological properties of malva nut gum (MNG) in different conditions of solvent (pH, ionic strength, and co-solutes addition). A small strain oscillation (0.1% strain) was used to investigate gelling properties of MNGs extracted with alkaline solutions compared to original MNG. Alkaline extracted MNGs showed higher storage modulus than did the original MNG. FT-IR of alkaline extracted MNGs showed carboxylic bonds with the reduction of galacturonic acids to increase the storage modulus compared to that of original MNG. Sodium chloride and calcium chloride strongly influenced the swelling of MNG, while the effect was smaller with K+ and Mg2+ ions. Addition of 5% sucrose into MNG solution increased gel strength of the polymer more than that of MNG solution containing 10% sucrose. Addition of guar gum into MNG solution increased storage modulus in either salts or acid containing system.