Abstract:
Four Authentic representative gum exudate samples from Acacia species namely
Acacia senegal var. senegal (ASG), Acacia mellifera (AMF), Acacia seyal var.
seyal (ASY), and Acacia tortilis var. raddiana (ATR), were characterized. The
moisture, ash, nitrogen, protein content, pH, specific optical rotation, and number
average molecular weight were found to be 9.76, 3.40, 0.327, 2.158, 4.94, -31.75,
and 0.24x106 for ASG, 9.56, 2.5, 0.630, 4.158, 4.53, -48.25, and 2.10x106 for
AMF, 8.35%, 3.13, 0.243%, 1.610%, 4.84, +56.00, and 2.95x106 for ASY and
8.49%, 2.05, 1.549%, 10.378%, 4.45, +86.75, and 2.06x106 for ATR respectively.
The 13C and 1H NMR spectra of gum samples showed similarity in individual
sugars components, but characteristic patterns of each gum, were observed. The
same functional groups were observed from the FTIR spectra of the gums. DSC
and TGA thermograms were characteristic for each gum. ASG, AMF, ASY, and
ATR gum emulsions were prepared, without the addition of weighting agents,
using different concentrations of Isopropyl Myristate (IPM). ASG and AMF gums
from the Vulgares series and ASY and ATR gums from the Gummiferae series
were blended in different proportions. Blends emulsions were prepared with 20%
IPM oil concentration. The morphology of gums and blends emulsions; over seven
days of incubation at 45C, exhibited spherical and dense droplets. Particles size
measurements, over a period of four weeks of incubation at 45C, showed that ATR
v
gum formed smaller and more stable droplets compared to the other gums. Phase
separation was observed at low oil concentration for all gum emulsions. Emulsions
of blends showed remarkable stability. The dye test confirmed that all gums and
blends emulsions are oil in water (O/W) system. The rheological flow profiles of
gums solutions at varying concentrations reflect a Newtonian flow for 50% and
40% concentrations and shear-thinning flow behavior for 30% and 20%
concentrations. All gums and blends, O/W, emulsions showed oil’s concentration
dependence; their profiles exhibited a shear-thinning flow behavior and a
Newtonian flow beyond 100 s-1 shear rate suggesting the alignment, of gums
molecules, with shear direction. The dynamic rheological study showed moduli
frequency dependence pattern for gum dispersions, gum emulsions, and blend
emulsions suggesting network formation of the gum molecules around the oil
droplets of the emulsions.
