R. Ndjouenkeu et al., WEAK GEL PROPERTIES OF KHAN FLOUR FROM BELSCHMIEDIA SP - A TRADITIONAL FOOD THICKENER FROM TROPICAL WEST-AFRICA, Food hydrocolloids, 9(3), 1995, pp. 165-172
Khan flour front Belschmiedia sp. has a long history of use in tropica
l West Africa as a food thickener. The polysaccharide fraction, which
is the principal constituent of the flour, shows typical polyelectroly
te behaviour in solution, giving an intrinsic viscosity of[eta] = 6.4
dl/g in 0.1 mol/dm(3) NaCl. The solutions comply with the general form
of shear thinning observed for disordered polysaccharide coils, with
close Cox-Merz superposition of eta(omega) and eta(gamma). The concen
tration dependence of 'zero shear' specific viscosity, however, shows
departure from dilute solution behaviour at c[eta] approximate to 2.5,
in comparison with the typical value of similar to 4.0 for most disor
dered polysaccharides, and the slope of log eta(sp) versus log c at hi
gher concentrations is unusually steep (similar to 2.5, in comparison
with the usual value of similar to 3.3). Similar behaviour has been re
ported previously for plant galactomannans, and attributed to chain-ch
ain associations augmenting physical entanglement. Khan flour hydrates
readily in water, and at concentrations within the approximate range
3-6% w/v gives 'weak gel' properties similar to those of ordered xanth
an (G' > G ''; little frequency clepeizdence in either modulus; eta(o
mega) > eta(gamma)). The gel-like character decreases with decreasing
concentration, and is attributed to weak interactions between swollen
particles within a surrounding matrix of dissolved polysaccharide.