Molecular characterisation and functional properties of gum arabic

Randall, RC

Abstract

Semi-PreParative gel permeation chromatography (gpc) was used to isolate several molecular mass components of gum arabic. The u. v. (218 nm) gpc elution profile showed the presence of several prominent peaks; however, only one major peak (FAw 3.8 x 10-9 g moll) and a minor peak (FAw 1.45 x 106 g mol-1) were observed in the
differential refractive index (R. I. ) gpc elution profile. The Rl. molecular mass distribution profile was also shown to be
representative of the true mass distribution of the gum.
Gram quantities of three apparently "pure" components of gum arabic were prepared using hydrophobic interaction chromatography. These components corresponded to the three major peaks observed in the u. v. gpc elution profile. Extensive physico-chemical analysis revealed that gum arabic consists of:-
a: a major protein deficient arabinogalactan representing
900/6o f the total gum mass:
b: a high molecular mass, protein rich (100A protein)
component, designated as an arabinogalactan-protein
complex which accounts for 9% of the total gum:
c: one or more protein enriched (50% protein) glycoprotein
components accounting for only 1% of the total gum.
Furthermore. the result of enzyme treatment indicates a
possible structural correlation between the arabinogalactan and the arabinogalactan-protein complex. This evidence also substantiates the so called 'Wattle Blossom" model which Is representative of the macrostructure of the high molecular mass arabinogalactan-protein complex.
The Newtonian rheological behaviour of aqueous gum Arabic solutions (up to 400/6 w/w) complements other experimental evidence, which strongly suggests that the gum's macromolecular structure is very compact for a polysaccharide. The unique emulsification properties of the gum were monitored by the development of standardised turbidimetric techniques. It was subsequently shown that enzyme and heat treatment of the gum had a similar effect of substantially reducing the emulsifying efficiency of
the gum. Both gum treatments effectively "denature" the
proteinaceous components of the gum and by consideration of other experimental evidence (adsorption characteristics of the components at the o/w interface) it was demonstrated that the high molecular mass arabinogalactan-protein complex is solely responsible for the gum' s emulsifying property.

Citation

Randall, R. Molecular characterisation and functional properties of gum arabic. (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Jul 13, 2017
• Publisher URL: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315411
• Related Public URLs: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315411
• Award Date: Apr 1, 1992