Physicochemical studies on the biopolymer inulin: A critical evaluation of its self‐aggregation, aggregate‐morphology, interaction with water, and thermal stability

Abstract

Physicochemical properties viz., aggregation, molar mass, shape, and size of chicory inulin in solution were determined by fluorimetry, DLS, SLS, TEM, and viscometry methods. The thermal stability of the biopolymer was examined by TGA, DTA, and DSC measurements. The water vapor adsorption of desiccated inulin was also studied by the isopiestic method, and the data were analyzed in the light of the BET equation. On the basis of the obstruction to ion conductance by the inulin aggregates in solution and analysis of the data, the extent of hydration of inulin in solution was estimated. The result was coupled with the intrinsic viscosity, [eta], of inulin to ascertain the shape of the biopolymer aggregates in aqueous solution. The critical aggregation concentration (cac) of inulin in aqueous as well as in salt solution was assessed by fluorimetry. The weight average molar mass, Mw , of inulin monomer and its aggregate was found to be 4468 and 1.03 x 10(6) g/mol, respectively, in aqueous solution. This aggregated mass was 2.4 x 10(6) g/mol in 0.5M NH(4)SCN solution. The [eta] values of the soft supramolecular aggregates in solution (without and with salt) were small and comparable with globular proteins evidencing spherical geometry of the biopolymer aggregates as supported by the TEM results. In DMSO, rod-like aggregates of inulin was found by the TEM study. The [eta] of the biopolymer in the DMSO medium was therefore, higher than that in the aqueous medium. Unlike aqueous medium, the aggregation in DMSO was not associated with a cac.

One‐pot, One‐step Synthesis of 2,5‐Diformylfuran from Carbohydrates over Mo‐Containing Keggin Heteropolyacids

“…The lower activity for the conversion of inulin was possibly owing to the use of DMSO solvent, known to be unfavorable for depolymerizing the polysaccharides. [38] Heterogenization of the Keggin HPA Although the PMo 12 HPA showed higher catalytic activity towards the production of DFF from fructose, its homogeneous nature made practical applications difficult because it could not be separated from the resulting mixture for recycling. As a solution, we partially substituted H + in the PMo 12 HPA by Cs + , obtaining series of Cs x H 3Àx PMo 12 (x = 0.5, 1.5, and 2.5) polyoxometalates that were known to be insoluble in water or any polar solvents.…”

Interaction of cationic hydroxyethylcellulose (JR400) and cationic hydrophobically modified hydroxyethylcellulose (LM200) with the amino-acid based anionic amphiphile Sodium N-Dodecanoyl Sarcosinate (SDDS) in aqueous medium

“…In this region, the complexed polymer-aggregates of overall globular geometry resulted. It is known that free species of spherical or globular geometry produce low and almost constant viscosity (Dan et al, 2009a). Beyond the CMC e point, associated complex (coacervate) disintegrated into smaller entities with change in configuration (elongation) by interaction with excess SDDS and the free micelles.…”

“…Due to unfavorable contact between the hydrophobic groups and water, these polymers have a tendency for self-aggregation and association with surfactants. Water soluble cationic celluloses and other biopolymers have been used in such studies (Burke & Palepu, 2001;Burke, Palepu, Hait, & Moulik, 2003;Dan, Ghosh, & Moulik, 2009a;Guillemet & Piculell, 1995;Hait, Majhi, Blume, & Moulik, 2003;.…”

Physical Properties of Inulin and Technological Applications

“…These phase transitions determine some properties such as the melting of crystals (melting temperature) and the change from the glassy into the rubbery state (glass transition temperature) (Miquel and Hall 2002). Other authors have noted that the most important properties of inulin are its high thermal stability, resistance to sticking, agglomeration, and crystallization (André et al 1996;Dan et al 2009;Glibowski and Pikus 2011;Kawai et al 2011;Pitarresi et al 2012;Ronkart et al 2009;Zimeri and Kokini 2003). These properties are directly influenced by the structure of the polysaccharide, i.e., thermal stability is related to the structure of the molecule, and stickiness, agglomeration, and crystallization are related to the collapse of the structure, defined according to Slade and Levine (1988) as the phenomenon where several time-dependent phase transformations are included.…”