Structure conformational and rheological characterisation of alfalfa seed (Medicago sativa L.) galactomannan. (15th March 2021)

• Record Type: Journal Article
• Authors: Hellebois, Thierry; Soukoulis, Christos; Xu, Xuan; Hausman, Jean-Francois; Shaplov, Alexander; Taoukis, Petros S.; Gaiani, Claire
• Is Part Of: Carbohydrate polymers. Volume 256(2021)
• Publication Date: 2021-03-15
• Subjects: Lucerne -- Galactomannan -- Viscoelasticity -- Flow behaviour -- Intrinsic viscosity -- Molecular weight -- Oscillatory thermo-rheology; Polysaccharides -- Periodicals; Polysaccharides -- Periodicals; Polysaccharides -- Périodiques; Electronic journals; 547.78
• DOI: 10.1016/j.carbpol.2020.117394
• Languages: English
• ISSNs: 0144-8617

Abstract

Highlights: A galactomannan was isolated from alfalfa ( Medicago sativa L.) seeds endosperm. A M/G ratio of 1.18, molar mass of 2 × 10 6 Da and intrinsic viscosity of 9.33 dL/g. The transition from the dilute to semi-dilute state was achieved at 0.306 % wt. The alfalfa gum exhibited weak gel properties at concentrations ≥3 % wt. Alfalfa gum exhibits similar rheological and molecular properties to fenugreek gum. Abstract: In the present work a galactomannan extract of low protein residue (< 1.3 % wt dry basis) was isolated from alfalfa ( Medicago sativa L.) seed endosperm meal. The alfalfa gum (AAG) comprised primarily mannose and galactose at a ratio of 1.18:1, had a molecular weight of 2 × 10 6 Da and a radius of gyration of 48.7 nm. The average intrinsic viscosity of the dilute AAG dispersions calculated using the modified Mark-Houwink, Huggins and Kraemer equations was 9.33 dLg −1 at 25 °C. The critical overlap concentration was estimated at 0.306 % whereas the concentration dependence of specific viscosity for the dilute and semi-dilute regimes was ∝ C 2.3 and C 4.2, respectively. The compliance to the Cox-Merz rule was satisfied at 1% of AAG, whereas a departure from superimposition was observed at higher concentrations. Viscoelasticity measurements demonstrated that AAG dispersions exhibit a predominant viscous character at 1 % wt, whereas a weak gel-like behaviour was reached at AAG concentrations ≥3 %.