عنوان

Molecular characterisation and functional properties of gum arabic

Number

TLets315411

Title Proper

Molecular characterisation and functional properties of gum arabic

General Material Designation

[Thesis]

First Statement of Responsibility

Randall, Richard Christopher

Name of Publisher, Distributor, etc.

University of Salford

Date of Publication, Distribution, etc.

1992

Dissertation or thesis details and type of degree

Thesis (Ph.D.)

Text preceding or following the note

1992

Text of Note

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.

Food technology & food microbiology

Randall, Richard Christopher

University of Salford

Electronic name

p

[Thesis]

276903

a

Y