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University of Khartoum (2003)

Characterization, Fractionation and Functional Studies on Some Acacia Gums

Ali, Naima Elnour Siddig

Titre : Characterization, Fractionation and Functional Studies on Some Acacia Gums.

Auteur : Ali, Naima Elnour Siddig

Université de soutenance : University of Khartoum

Grade : Doctor of Philosophy (PhD) 2003

Résumé
Some Acacia gums (A.senegal, A.seyal, A.polyacantha, A.laeta and A.mellifera) were subjected to investigation (characterization, fractionation and functional studies). In order to illustrate some of the information required for identification and differentiation between A.senegal gum and the four most important Acacia gums produced in the Sudan. Characterization of above mentioned gums (moisture contents, ash content, pH, viscosity, intrinsic viscosity, specific rotation, equivalent weight, uronic acid content, mineral composition and amino acid composition) was carried out and the data obtained reflect the compositional differences between these gums. Hydrophobic interaction chromatography (HIC) fractionation was also carried out for A.senegal, A.seyal, A.polyacantha, and A.laeta and the fractions obtained were characterized to asses some of the structural features of these gums. The results revealed some differences in the fraction recovery as well as, the nitrogen content, molecular weight , molecular weight distribution, amino acids and emulsifying properties of the fractions. The molecular weight and the molecular weight distribution of the five Acacia gums were also determined. The data obtained shows that A.seyal was found to have the highest molecular weight followed by A.mellifera, A.laeta, A.polyacantha and then A. senegal. The emulsifying properties of these Acacia gums were also studied at different concentrations (5, 10, 15 and 20%). The most amazing results obtained shows that : using 5% and 20% gum solutions gave almost the same emulsifying properties in all gums studied. And that the five Acacia gums differ in their emulsifying stability. The rheological properties of those gums (flow behaviour and the oscillation measurement) were determined at different concentration (10, 20, 30, 40, and 50%). And the results revealed that A.senegal exhibits a Newtonian behaviour at most of the concentrations studied, A.laeta and A.mellifera exhibited a slight shear thinning, whereas, A.polyacantha showed a clear shear thinning behaviour. And the oscillation measurements also showed the same differences between these gums. The effect of aging on the flow behaviour and the oscillation measurement of the three acacia gums were also studied. And the data obtained shows that A.senegal was the most stable gum followed by A.polyacantha, whereas, A.laeta showed inconsistency in the flow behaviour where the viscosity increased with age then decreased. A.senegal oscillation measurements showed a semi-concentrated solution behaviour for fresh and three days age then the solution become a dilute solution after six days and again a concentrated solution after nine days. A.polyacantha gum was a gel like solution when fresh at the concentration under investigation and kept as gel solution through out the period of the study. A.laeta was a semi-concentrated solution when fresh then become a gel solution after three days and slightly transformed to concentrated solution again after six and nine days

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