Utilization of gum exudates from some acacia species

Gum Exudates are used widely in various industries, some of which are the food, cosmetics, pharmaceuticals, adhesives, wood and paper industries. In Ghana, most industries import these gum exudates, even though there are a lot of tree species in Ghana that exudes gums. The studies on the physical, rheological and chemical properties of local gum from Acacia polyacantha Acacia Sieberiana and Acacia dudgeoni in comparison with a commercial gum from Acacia senegal, indicates that, the local gums had acceptable levels of moisture content, (which is not more than 15%), less than 1.0% insoluble matter, less than 0.5% total ash value, and acid insoluble ash. They dissolved in water and Sodium Hydroxide, but not in most organic solvent. They showed Iaevarotatory optical rotation in water, and maintained a relative stable pH with time. The local gums like the commercial gum did not contain any starch or tannins. It was confirmed from the sugar reactions that, their sugar composition are Rhamnose, Arabinose, Galactose, and Glucuronc acid. Like the commercial gum, their viscosities increased with concentration and decreased with time. The viscosities of these gum mucilage rises with pH till a pH of about 5 and then falls as the pH increases from 6 to 14. All the gums exhibited Non-Newtonian flow. There was no significant change in flow curves obtained from the plot of shear rate against shear stress with varying time, concentration, and pH of the gum mucilage. It can then be concluded that the local gums could be used as suitable substitute for the commercially imported ones. It was recommended therefore that the plants produced gums be cultivated in commercial quantities to facilitate their use as substitutes for the imported ones, and that large plantations of the species should be encouraged to sustain the supply. List of Tables Table 4.1 The macroscopic features of the various gums. 4.2 The solubility characteristics of the various gums. 4.3 The refractive index and optical rotation. 4.4 The percentage moisture content. 4.5 The percentage insoluble matter. 4.6 The total ash value. 4.7 Acid insoluble ash. 4.8 Standard equations. 4.9 Identity test and reaction. 4.10 Sugar reactions. 4.11 Aldose sugar content in the unhydrolysed gum. 4.12 Aldose sugar content in the hydrolysed gum. 4.13 Uronic acid content in the unhydrolysed gum. List of Figures Figure 4.1 Graph of pH of gum mucilage against time in days. 4.2 Graph of time (sec) of 100 revolutions against viscosity (centipoise). 4.3 Graph of viscosity against time for the four gums. 4.4 Rheologram of the varying time for Acacia senegal gum. 4.5 Rheologram of varying time for Acacia polyacantha gum. 4.6 Rheologram of varying time for Acacia sieberiana gum. 4.7 Rheologram of varying time for Acacia dugeoni gum. 4.8 Graph of viscosity against concentration for the four gums. 4.9 Rheologram of varying concentration for Acacia senegal gum. 4.10 Rheologram of varying concentration for Acacia polyacantha gum. 4.11 Rheologram of varying concentration for Acacia sieberiana gum. 4.12 Rheologram of varying concentration for Acaciá dudgeoni gum. 4.13 Graph of viscosity against pH for Acacia senegal gum. 4.14 Graph of viscosity against pH for Acacia polyacantha gum. 4.15 Graph of viscosity against pH for Acacia sieberiana gum. 4.16 Graph of viscosity against pH for Acacia dudgeoni gum. 4.17 Rheologram of varying pH for Acacia senegal gum. 4.18 Rheologram of varying pH for Acacia polyacantha gum. 4.19 Rheologram of varying pH for Acacia sieberiana gum. 4.20 Rheologram of varying pH for Acacia dudgeoni gum.

Source: KNUST