An investigation of the molecular structure, composition and biophysical properties of gum Arabic

2.50
Hdl Handle:
http://hdl.handle.net/2436/608784
Title:
An investigation of the molecular structure, composition and biophysical properties of gum Arabic
Authors:
Gashua, Ibrahim Babale
Abstract:
Acacia senegal and Acacia seyal are important agroforestry cash crops indigenous to several countries of sub-Saharan Africa, including Nigeria. The gum exudate produced by these species is termed gum Arabic which is an approved food additive (E414), primarily used as an emulsifier. In the current study, the molecular structure, composition and biophysical properties of gum samples harvested from mature trees of Acacia senegal at two specific ecolocations in Nigeria (NG1 and NG2), have been investigated together with two previously characterised gum samples harvested from A. senegal and A. seyal originating from Sudan. The monosaccharide sugar composition analyses have shown that the A. seyal gum had a lower rhamnose and glucuronic acid content than the A. senegal gum, but had higher arabinose content. No significant difference was observed between the sugar composition of the A. senegal gums from Sudan and Nigeria. The total protein content of the Nigerian gum samples were significantly higher than recorded for the Sudanese samples. The principal amino acids present in all the gum samples are hydroxyproline, serine, aspartame, threonine and proline which is in agreement with literature values. The hydrodynamic size of the molecules present in the gums was studied using dynamic light scattering and it was found that molecular association occurred in solution over time which was inhibited in the presence of an electrolyte. The comparison of droplet size distribution for emulsions prepared with A. senegal (NG1) and A. seyal gum samples showed that A. senegal sample was a better emulsifier than the A. seyal. Multilayer adsorption of the samples onto polystyrene latex particles was observed, which resulted in an increase in thickness of the adsorbed layer as a consequence of the interaction between the protein and carbohydrate within the molecules adsorbed on the emulsion surface. Preliminary analyses of the gums using transmission electron microscopy showed the presence of varied macromolecules, ranging in size from ~12 - ~60 nm. Immuno-gold negative staining (using JIM8 monoclonal antibody) indicated clear labelling of arabinogalactan-proteins present in the gums harvested from A. senegal, the labelling of the A. seyal sample was inconclusive. In summary, the data presented represents the first detailed comparison of the structure, composition and physicochemical characteristics of Nigerian Acacia gum exudates versus Sudanese samples (main global supplier) which have shown that gum obtained from Nigerian sources is a viable alternative to ensure future supply of this valuable natural resource.
Issue Date:
Feb-2016
URI:
http://hdl.handle.net/2436/608784
Type:
Thesis
Language:
en
Description:
A thesis submitted in partial fulfilment of the requirements of the University of Wolverhampton for the degree of Doctor of Philosophy
Appears in Collections:
E-Theses

Full metadata record

DC FieldValue Language
dc.contributor.authorGashua, Ibrahim Babaleen
dc.date.accessioned2016-05-10T11:04:48Zen
dc.date.available2016-05-10T11:04:48Zen
dc.date.issued2016-02en
dc.identifier.urihttp://hdl.handle.net/2436/608784en
dc.descriptionA thesis submitted in partial fulfilment of the requirements of the University of Wolverhampton for the degree of Doctor of Philosophyen
dc.description.abstractAcacia senegal and Acacia seyal are important agroforestry cash crops indigenous to several countries of sub-Saharan Africa, including Nigeria. The gum exudate produced by these species is termed gum Arabic which is an approved food additive (E414), primarily used as an emulsifier. In the current study, the molecular structure, composition and biophysical properties of gum samples harvested from mature trees of Acacia senegal at two specific ecolocations in Nigeria (NG1 and NG2), have been investigated together with two previously characterised gum samples harvested from A. senegal and A. seyal originating from Sudan. The monosaccharide sugar composition analyses have shown that the A. seyal gum had a lower rhamnose and glucuronic acid content than the A. senegal gum, but had higher arabinose content. No significant difference was observed between the sugar composition of the A. senegal gums from Sudan and Nigeria. The total protein content of the Nigerian gum samples were significantly higher than recorded for the Sudanese samples. The principal amino acids present in all the gum samples are hydroxyproline, serine, aspartame, threonine and proline which is in agreement with literature values. The hydrodynamic size of the molecules present in the gums was studied using dynamic light scattering and it was found that molecular association occurred in solution over time which was inhibited in the presence of an electrolyte. The comparison of droplet size distribution for emulsions prepared with A. senegal (NG1) and A. seyal gum samples showed that A. senegal sample was a better emulsifier than the A. seyal. Multilayer adsorption of the samples onto polystyrene latex particles was observed, which resulted in an increase in thickness of the adsorbed layer as a consequence of the interaction between the protein and carbohydrate within the molecules adsorbed on the emulsion surface. Preliminary analyses of the gums using transmission electron microscopy showed the presence of varied macromolecules, ranging in size from ~12 - ~60 nm. Immuno-gold negative staining (using JIM8 monoclonal antibody) indicated clear labelling of arabinogalactan-proteins present in the gums harvested from A. senegal, the labelling of the A. seyal sample was inconclusive. In summary, the data presented represents the first detailed comparison of the structure, composition and physicochemical characteristics of Nigerian Acacia gum exudates versus Sudanese samples (main global supplier) which have shown that gum obtained from Nigerian sources is a viable alternative to ensure future supply of this valuable natural resource.en
dc.language.isoenen
dc.subjectGum Arabicen
dc.subjectAcacia senegai-NG 1en
dc.subjectGum exudateen
dc.subjectGujbaen
dc.subjectBiophysical Acacia seyalen
dc.subjectArabinogalactan-proteinen
dc.titleAn investigation of the molecular structure, composition and biophysical properties of gum Arabicen
dc.typeThesisen
All Items in WIRE are protected by copyright, with all rights reserved, unless otherwise indicated.