Rheological characterization of RG-I chicory root pectin extracted by hot alkali and chelators

Abstract

This work aimed to extract gelatinous chicory root pectin (CRP) and evaluated the rheological behavior of the dispersions and gels. CRP was extracted by citric acid (CEP), alkaline (AEP), ammonium oxalate (OEP) and sodium citrate (SEP). The yield, molecular weight (Mw) and the degree of esterification (DE) of pectin samples varied from 8.8 to 14.8% (w/w), 204 to 336 k Da and 4.0 to 47.4%, respectively. AFM studies showed self-organize on mica of CEP, revealing a random coil conformation due to the interaction of multiple branching, whereas, AEP exhibited long linear filamentous structures. The flow behavior study verified the pseudoplastic character of CEP and SEP at 25 °C, while OEP and AEP belonged to dilatant fluid, besides, a closed hysteresis loop was observed when the CEP concentration increased to 1.5%. OEP gel was thermo insensitive and stiff, AEP gel presented most sensitive to calcium ion but more brittle, and SEP was observed a weak syneresis in spite of the poor gelation property. The texture analysis indicated OEP gel had a superior firmness and chewiness. These findings demonstrated that CRP may be attractive as a thickener or gelling agent to modulate textures of sugar-free and calcium content food.

Keywords: Chicory root pectin; Gel-mechanism; Nanostructure; Rheological characterization; Texture.