Search

Understanding the intricate relationships between the fine structure of xanthan on the assembly of konjac glucomannan (KGM) and xanthan is crucial for developing KGM/xanthan synergistic interaction gels. A combination of micro-differential scanning calorimetry, rheometry and atomic force microscopy were employed to explore the assembly process of KGM and xanthan with varying fine structures. Xanthan possessing standard acetyl (4.57%) and high pyruvate group contents (6.49%)(SA/HP) exhibited type-A and type-B bindings when interacting with KGM through cooling process. Decreasing these group contents effectively reduced type-B binding. Additionally, removal of pyruvate groups to 5.53% amplified type-A binding and gel strength from 258 Pa to 653 Pa, thanks to the improved helical structure forming ability of xanthan. Decreasing acetyl groups also intensified type-A interaction and gel strength from 258 Pa to 872 Pa. This stemmed from the formation of more stable assembly structure of xanthan and KGM, compared to the helical structure of deacetylated xanthan. These findings hold promise for the rational design of KGM/xanthan systems for versatile applications. [Display omitted] • Decreasing acetyl and pyruvate group contents enhanced type-A binding. • Decreasing acetyl and pyruvate group contents eliminated type-B binding. • Self-aggregation of xanthan occurred in KGM-SA/VLP and KGM-LA/LP. • The extensive binding of xanthan and KGM improved the gel hardness. [ABSTRACT FROM AUTHOR]

Combined with rheology and micro-DSC methods, atomic force microscopy was applied to explore the synergistic binding ways of KGM and xanthan with high pyruvate group content at a total polymer concentration of 0.5% when mixed in ratios of 9:1 (K9X1) to 1:9 (K1X9). Upon cooling, Type A and B, corresponding to the peak Ⅰ (40-25 °C) and Ⅱ (55-40 °C) on G ′ curves respectively, were evidenced for KGM/xanthan composites. Type A binding was associated with the interactions of KGM and helical structures of xanthan and was mainly responsible for the building up of three-dimensional network for K5X5, K4X6, K3X7, K2X8 and K1X9 (with no remarkable flow after inversion). The maximum Type A binding occurred at K4X6, K3X7, and K2X8 samples with the relatively higher proportions of thick bundles (1.5–2.5 nm), enthalpy value, G ′ values and gel hardness. Type B binding was related to the interactions involving KGM and disordered xanthan molecules, and was positively related to the pyruvate group content and negatively correlated with the cation concentration and xanthan content. This work is helpful in comprehensively understanding the binding ways of KGM and xanthan with high pyruvate group content and are valuable for the exploration of binding ways between food hydrocolloids. [Display omitted] • AFM was used to explore the synergistic binding of KGM and xanthan. • Type A and B binding were evidenced for KGM/xanthan solution upon cooling. • Type A was associated with the interaction of KGM and helix of xanthan. • The maximum Type A binding occurred at K4X6, K3X7, and K2X8. • Type B was related to the interaction of KGM and disordered xanthan molecules. [ABSTRACT FROM AUTHOR]

From a microstructural point of view, this work concerns how deacetylation improves the practical characteristics of deacetylated-konjac glucomannan/agar (DK/A) composite films. As disclosed by infrared spectroscopy and X-ray diffraction, the deacetylation of konjac glucomannan (KGM) enhanced the chain interactions in DK/A composites and suppressed the realignment of agar molecules into crystallites. The enhanced associations between acetyl-free regions of KGM and agar reduced the exposure of OH groups and thus increased the hydrophobicity of the composites. Besides, the partial removal of acetyl groups allowed shortened distances between chains; consequently, denser composite matrices emerged with lower water vapor permeability and higher tensile strength. Also, the KGM deacetylation increased the matrix flexibility and elongation at break for DK/A composites, associated with the hindered rearrangement of agar chains. Thus, altering the deacetylation degree of KGM may be an effective way to design KGM-based composites with improved hydrophobicity and mechanical performance. [ABSTRACT FROM AUTHOR]

Microstructure and Mechanical/Hydrophilic Features of Agar-Based Films Incorporated with Konjac Glucomannan. The authors wish to make the following correction to this paper [[1]]: in the original version of the published article, there is a mistake in Equation (1) on Page 3. Reference 1 Qiao D., Tu W., Zhong L., Wang Z., Zhang B., Jiang F. Microstructure and mechanical/hydrophilic features of agar-based films incorporated with konjac glucomannan. [Extracted from the article]

Here, we tailored the multi-level structural and practical (mechanical/hydrophilic) features of gelatin films by varying the konjac glucomannan (KGM) content and the film-forming temperatures (25 and 40 °C). The addition of KGM apparently improved the mechanical properties and properly increased the hydrophilicity. With the lower temperature (25 °C), the increase in KGM reduced the gelatin crystallites of films, with detectable KGM–gelatin interactions, nanostructures, and micron-scale cracks. These structural features, with increased KGM and negligibly-occurred derivatizations, caused initially an insignificant decrease and then an increase in the strength, with a generally-increased elongation. The higher temperature (40 °C) could reduce the strength and slightly increase the elongation, related to the reduced crystallites of especially gelatin. With this higher temperature, the increase in KGM concurrently increased the strength and the elongation, mainly associated with the increased KGM and crystallites. Additionally, the increase in KGM made the film more hydrophilic; the multi-scale structural changes of films did not dominantly affect the changing trend of hydrophilicity. [ABSTRACT FROM AUTHOR]

Different characterization methods spanning length scales from molecular to micron scale were applied to inspect the microstructures and mechanical/hydrophilic features of agar/konjac glucomannan (KGM) films prepared under different drying temperatures (40 and 60 °C). Note that the lower preparation temperature (40 °C) could increase the strength and elongation of agar/KGM films at high KGM levels (18:82 wt/wt KGM-agar, or higher). This was related to the variations in the film multi-scale structures with the increment of KGM content: the reduced crystallinity, the increased perfection of nanoscale orders at some KGM amounts, and the negligibly-changed morphology and molecular chemical structure under 40 °C preparation temperature. These structural changes initially decreased the film tensile strength, and subsequently increased the film strength and elongation with increasing KGM content. Moreover, under the higher drying temperature (60 °C), the increased KGM content could concurrently reduce the strength and elongation for the films, associated with probable phase separations on nano and smaller scales. In addition, the increased KGM amount tended to make the film more hydrophilic, whereas the changes in the film structures did not dominantly affect the changing trend of hydrophilicity. [ABSTRACT FROM AUTHOR]