Impact of ethanol addition on the behaviour of xanthan gum in aqueous media. (November 2021)

• Record Type: Journal Article
• Authors: Brunchi, Cristina-Eliza; Morariu, Simona; Bercea, Maria
• Is Part Of: Food hydrocolloids. Volume 120(2021)
• Publication Date: 2021-11
• Subjects: Xanthan gum -- Ethanol addition -- Turbidity -- Preferential adsorption -- Viscosity -- Aggregation; Hydrocolloids -- Periodicals; Food additives -- Periodicals; Colloïdes -- Périodiques; Aliments -- Additifs -- Périodiques; Colloids; Food additives; Periodicals; Electronic journals; 664.06
• DOI: 10.1016/j.foodhyd.2021.106928
• Languages: English
• ISSNs: 0268-005X

Abstract

Abstract: The effect of ethanol (EtOH) addition on the behaviour of xanthan gum (XG) chains in water (W) was investigated at 25 °C by using turbidimetry, zeta potential, refractometry and viscometry. The presence of EtOH (nonsolvent) in aqueous solution of XG reduces the thermodynamic quality of solvent and increases the polymer-polymer contacts ( i.e., electrostatic, H-bonding or hydrophobic interactions). Thus, the transition from an expanded chain conformation to a more compact one was evidenced by viscometry, zeta potential masurements and refractometry while the aggregation of macromolecules or phase separation were observed by turbidimetry. A phase diagram for XG in solvent/nonsolvent mixtures was provided. For volumetric fractions of ethanol ( ϕ EtOH ) higher than 0.3, zeta potential increases above −30 mV and the aggregation of xanthan chains takes place. Measurements of refractive indices were used to determine the preferential adsorption coefficient ( λ 1 ) for different volumetric fractions of ethanol. The parameter λ 1 quantifies the polymer chain affinity for one component of the solvent/nonsolvent mixtures. The polyelectrolyte effect of XG chains in solution and the variable polarity as a function of W/EtOH composition influence the overall thermodynamic behaviour of XG assessed through the viscometric parameters determined by using the Wolf approach. Graphical abstract: Image 1 Highlights: XG chains undergo aggregation and phase separation in presence of high EtOH content. Phase transitions of XG/Water/EtOH systems are reflected in the variation of turbidity. Zeta potential increases by EtOH addition suggesting the emergence of heterogeneity. Helix-coil transition occurs when water is preferentially adsorbed by XG chains.