Rheological and physio-chemical properties of two acacia gums and stability of their emulsions

Abstract EN

Acacia plants are leguminous tree species that are well adapted to Sudan and Sahelian agro-ecology of Africa.

In Sudan, gum Arabic plays a significant role in rural life and economic activities.

The study aims to characterize two Acacia gums, including their emulsions and blends.

Acacia Senegal var.

Senegal (ASG) and Acacia mellifera (AMF) gum emulsions were prepared without the addition of weighting agents or preservatives using different concentrations of Isopropyl Myristate (IPM).

The viscosity of ASG and AMF gum emulsions showed oil concentration dependence and displayed Newtonian flow behaviour at a shear rate beyond 50s-1.

Shear-thinning flow was also observed at a low shear rate for both gums’ emulsions which is more pronounced for ASG, suggesting the alignment of gum molecules with the shear direction.

The dynamic rheological study showed a moduli frequency dependence pattern suggesting network formation of the gum molecules about the emulsion’s oil droplets.

The morphology of gum emulsions exhibited spherical and dense droplets.

Over four weeks of incubation at 45°C, particle size measurements showed that AMF gum formed smaller and more stable droplets than ASG.

Phase separation was observed at low oil concentration for both gum emulsions.

The dye test confirmed that ASG and AMF gum constitute an oil in water (O/W) emulsion systems.

Emulsion of blended Vulgares gums (ASG & AMF, 1:1 ratio) was prepared with the optimum oil concentration, which was 20%, showing enhancement of stability and rheological properties.