Rheological and functional properties of asafoetida gum.

ABSTRACT

The asafoetida gum was extracted and purified from oleo-gum-resin of Ferula assa foetida root and characterized by high pressure anions exchange chromatography after acidic hydrolysis. It was composed of GalAraRhaGlcA with the ratio 11.55.02.11.0. This monosaccharide composition was found similar to that of a commercial Arabic gum which exhibited a GalAraRhaGlcA ratio of 11.75.43.21.0. As the Arabic gum is currently used for its emulsifying properties, the two gums were evaluated for their functional and rheological behaviors. Surface and interfacial tensions values were lower for asafoetida gum compared to Arabic gum. Critical micelle concentration was achieved at concentrations of 0.5% w/w and 1% w/w for asafoetida and Arabic gums, respectively. Values of emulsion capacity, emulsion stability and foaming properties were considerably higher for asafoetida gum in contrast to emulsion activity index that was lower than that of Arabic gum. As those of Arabic gum, solutions of asafoetida gum (2-30% w/w) exhibited Newtonian flow behavior at shear rates between 1 and 500 s-1. Apparent viscosities of Arabic and asafoetida gums were close and logically decreased by increasing temperature (10-80 °C). Higher viscosities were achieved at higher pH and CaCl2 concentrations.