| Fenugreek seed galactomannan was extracted, purified and characterized with respect to chemical structure, molecular weight (Mw), intrinsic viscosity ([&eegr;]), surface activity and rheological properties. Methylation analysis confirmed fenugreek as a (1→4) linked mannan chain with galactosyl units linked at C-6. Surface activity displayed by the gum was reduced with protein removal. Fenugreek gum solutions exhibited typical random coil behaviour. HPSEC-RALLS and light scattering gave a Mw of 1.418 × 106 g/mol and 1.54 × 106 g/mol, respectively. The [&eegr;] of fenugreek gum was 9.61 dl/g. Compared to guar and locust bean gum, fenugreek gum had a more compact structure. Fenugreek gum was susceptible to β-mannanase hydrolysis, suggesting unbranched residues occur in groups. The majority of hydrolysis products were insoluble in 30% ethanol, had a Mw around 4.0 × 105 g/mol and completely substituted mannan chains. 13C-NMR revealed the 80% ethanol insoluble fraction of the hydrolysate contained single and consecutive unbranched mannose residues. |
