Characterization of galactomannans isolated from legume endosperms of Caesalpinioideae and Faboideae subfamilies by multidetection aqueous SEC

Properties of galactomannans and their textile-related applications-A concise review

Galactomannans are reserve carbohydrates in legume plants and are primarily extracted from their seeds. They contain galactose side chains throughout the mannose backbone and have unique features such as emulsifying, thickening, and gelling together with biodegradability, biocompatibility, and non-toxicity, which make them an appealing material. Guar gum and locust bean gum mainly are used in all galactomannan needed applications. Nonetheless, tara gum and fenugreek gum have also attracted considerable attention in recent decades. Despite the increased usage of galactomannans in the textile-related fields in recent years, there is no review article published yet. To fill this gap and to demonstrate the striking and increasing importance of galactomannans, a concise summary of the properties of common galactomannans and their comparisons is given first, followed by an account of recent developments and applications of galactomannans in the textile-related fields. The associated potential opportunities are also provided at the end of this review.

Effects of the Hofmeister anion series salts on the rheological properties of Sesbania cannabina galactomannan

Sesbania cannabina galactomannan (2%) solutions added with strongly hydrated ions (Na₂CO₃, NaH₂PO₄, NaCl) and weakly hydrated ions (NaNO₃) at different ionic strengths were rheologically characterized. The four selected salts dramatically decreased the intrinsic viscosity of galactomannan solution in the following order of effectiveness: Na₂CO₃ < NaH₂PO₄ < NaCl < NaNO₃. This conforms effectively to the Hofmeister anion series. Moreover, salt addition increased the viscosity of galactomannan solution when the ionic strength was 1 mmol/kg, which related to an increased occurrence of intermolecular interactions. As increasing ionic strength, galactomannan chains may tend to contract or expand due to the presence of strongly or weakly hydrated ions, thereby decreasing the viscosity. These phenomena were demonstrated by zeta potential measurement and again observed in dynamic viscoelasticity measurement. Overall, this property can be used to manipulate the rheological properties of galactomannan in food gums to obtain gums of high quality for enhancing consumer goods.

Isolation, physical, structural characterization and in vitro prebiotic activity of a galactomannan extracted from endosperm splits of Chinese Sesbania cannabina seeds

The purpose of this study was to identify and determine the physical and structural characterization of the water-soluble galactomannan extracted from endosperm splits of Chinese S. cannabina seeds. The Sesbania galactomannan (SP) was extracted and purified using a novel method with a high yield (40.3 ± 7.2%). The molecular structure of SP was determined by monosaccharide composition, FTIR and NMR spectroscopy. The structural data showed that SP was galactomannan which composed by a β-(1/4)-linked mannose backbone with galactopyranosyl residues attached through α-(1/6) linkages. The constant mannose/galactose (M/G) ratio and average molecular weight (M_w) of SP was 1.6:1 and 2.16 × 10⁵ g/mol, respectively. The physical results revealed that SP had many branches on the backbone and existed as a random coil state in aqueous solution. SP was a good biopolymer which had smooth and clearer surface with homogeneous composition, and had some degree of crystallinity and prebiotic activity. As a consequence, SP could be a potential prebiotic and was expected to be suitable for applications in food, pharmaceutical, biomedical or cosmetic industries as a promising new biomaterial.

Semi-dilute galactomannan solutions: observations on viscosity scaling behavior of guar gum

Based on experimental work involving evaluation of viscosity enhancement of aqueous solutions by high molecular weight guar gum, we have observed that the shear viscosity scaling exponent b for semi-dilute solutions, ηsp ~ (c[η])(b), is sensitive to molecular weight, being approximately 4.7 for native samples and decreasing progressively as Mw is lowered. The critical overlap parameter demarcating the dilute and semi-dilute regimes also depends on the molecular weight as (c[η])* ~Mw(-0.82). Consequently, viscosity-concentration plots fail to achieve overlap using only specific viscosity and overlap concentration as reducing variables, a commonly accepted empiricism for random-coil polysaccharides. To bridge the gap, we propose to account for water solubility, its temperature dependence and the resulting chain flexibility as additional factors to fully describe the solution behavior of these highly-important raw materials.

Characterization and rheological study of the galactomannan extracted from seeds of Cassia grandis

Galactomannan extracted from seeds of Cassia grandis with 0.1M NaCl, followed by ethanol precipitation, presented a yield of 36 ± 8%. The polysaccharide has a constant mannose/galactose ratio (2.44:1). Methylation analysis, one and two dimensional NMR spectroscopy confirmed that the polysaccharide has a central core composed of 4-linked β-mannose units, with branches of galactose, linked to the carbohydrate core through α(1-6) linkage. The amorphous nature of the galactomannan was confirmed by X-ray diffraction. Rheological characterization exhibited Newtonian plateaus followed by shear-thinning zones characteristic of polymer solutions up to 1.5% (w/v) and above this value the system exhibited yield stress associated with a weak gel. Adjusting stress-strain curves confirmed a 1.6% (w/v) as the galactomannan concentration value for the sol-gel transition. These results indicate that the galactomannan extracted from C. grandis seeds presents rheological characteristics suitable for applications in pharmaceutical, biomedical, cosmetic and food industries.

Viscosimetric detection in size-exclusion chromatography (SEC/GPC): The Goldwasser method and beyond

Size-exclusion chromatography (SEC or GPC) is the most widely used separation method to characterize polymers. The high level of complexity of most polymeric materials necessitates the use of not only concentration-sensitive detection but also structure-sensitive detection. Viscometry is usually used in conjunction with a concentration-sensitive detector and universal calibration to determine molecular weights of polymers. Goldwasser proposed to use a viscometer as a single detector to determine number-average molecular weights, M(n) (ACS Symposium Series, 521, 143). The method is particularly of interest when concentration-sensitive detection is not available, because the sample is isorefractive or not UV-absorbing, or because composition is not constant (copolymers). It has known very little applications so far. It actually does not only allow determining M(n), but also the number hydrodynamic volume distribution. This opens a wider range of applications for the Goldwasser method. Size-exclusion chromatography only yields inaccurate molecular weight distributions for some complex branched polymers. Hydrodynamic volume distributions have then a strong potential for comparative studies owing to their far higher accuracy. Our experimental tests highlight the fact that the method is highly sensitive to noise and careful optimization of the injection concentration is needed, but number distribution can be obtained as well as M(n).