Liquid crystal formation and rheological study in aqueous blends of xanthan/acacia gum. (April 2015)

• Record Type: Journal Article
• Authors: Rwei, Syang-Peng; Nguyen, Tuan-Anh; Chien-Jung Lee, Jenny; Chiang, Whe-Yi
• Is Part Of: Food hydrocolloids. Volume 46(2015:Apr.)
• Page Start: 52
• Page End: 58
• Publication Date: 2015-04
• Subjects: Xanthan gum (XG) -- Acacia gum (AG) -- AX-W system -- A-XW system -- Liquid crystal (LC) -- Strand-like LC -- Dispersed LC; Hydrocolloids -- Periodicals; Food additives -- Periodicals; Colloïdes -- Périodiques; Aliments -- Additifs -- Périodiques; Colloids; Food additives; Periodicals; Electronic journals; 664.06
• DOI: 10.1016/j.foodhyd.2014.12.013
• Languages: English
• ISSNs: 0268-005X

Abstract

Abstract: In this work, the liquid crystalline (LC) phase in an aqueous acacia/xanthan gum (AG/XG) system was determined by optical and rheological analyses. The experimental results indicate that with moderate blending ratios, theAX -W tertiary system, in which AG and XG were simultaneously dissolved together in H2 O, formed a dispersed LC structure while the A-XW tertiary system, in which AG was mixed with ready aqueous XG, formed a strand-like LC structure. This morphological difference is attributed to the possibility of AG/H2 O coupling to form a continuous non-LC domain; this coupling was not observed in AG/XG blends with extremely low (10/10), or high (55/10) ratios. A schematic model that explains the morphological results is proposed. Measurements of viscosity verify the morphological observations. AG/H2 O coupling forms a lubricant with near-Newtonian behavior. The power law indices increased with the AG content to 45 wt% for bothAX -W and A-XW systems. In contrast, increasing the XG content promoted the non-Newtonian behavior of the blends. Finally, aqueous XG with 10 wt% solid content acted as a strong gel, which was insensitive to variation in temperature. However, the addition of AG to such blends reduced the viscosity and increased their sensitivity to temperature. Graphical abstract: Highlights: Phase diagram of xanthan/Acacia/H2 O sys. depends on the way gums are introduced. AG, XG were simultaneously dissolved in H2 O to form a dispersed LC phase (AX -W). AG was mixed with ready aqueous XG to form a strand-like LC phase (A-XW ). A Newtonian fluid is got forAX -W with low XG% due to AG/H2 O being a lubricant. Orientation under shearing within the XG phase resulted in shear thinning of A-XW .