Rheological Study of Agar Hydrogels for Soft Capsule Shells.

The rheological properties of agar hydrogels were investigated. The agar gels were prepared by mixing an aqueous solution of agar-agar with glycerin, sorbitol, citric acid, sodium citrate, and sodium chloride at various concentrations. Sodium citrate, citric acid, and also their mixture had the most significant effect on the viscosity of the agar gels. Adding citric acid to the agar-gel composition reduced the viscosity whereas addition of sodium citrate increased it. Hysteresis loops were constructed for various compositions. [ABSTRACT FROM AUTHOR]