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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]

• Adding NaCl or CaCl 2 eliminated the type-B binding. • The presence of NaCl enhanced the type-A synergistic binding. • Type-A binding was improved by low concentration of CaCl 2. • Addition of excessive CaCl 2 reduced the type-A binding. Synergistic interaction gels could be formed by synergistic type-A and type-B bindings between konjac glucomannan (KGM) and xanthan during cooling. Adding salt ions significantly altered those bindings and thus the gel-related properties. The results showed that adding NaCl or CaCl 2 eliminated type-B binding due to an electrostatic shielding effect. Adding NaCl or CaCl 2 (3 and 6 mM) enhanced type-A binding by neutralizing the negative charge of COOH and reducing the electrostatic repulsion among xanthan chains, as evidenced by an increase in the onset temperature of exotherm peak, the formation of more parallel multiple filaments, and an increase in aggregation structures (>1.0 nm) and gel hardness. When CaCl 2 concentration was higher, Ca2+ bridged side-chain clusters into more complex structures, which would hardly participate in the formation of helical structures and weaken type-A binding. The results obtained are beneficial for the rational design and preparation of KGM/xanthan gels with synergistic interaction. [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]

The properties (e.g., viscosity, sol-gel transition, and mechanical characteristics) of polysaccharides are crucial for their food applications. This work discloses how xanthan gum (XG) incorporation tailors the performance of an agar/konjac glucomannan (KGM) system. As reflected by rheological and thermal analyses, an increasing content of XG added could strengthen the chain entanglement in the resulting ternary solution with strong KGM-XG binding (an exothermic event). For example, a ternary system with a 16% XG content (AKX-16%) showed simultaneous increases in the zero-shear viscosity (about 5.5 times that of the binary counterpart AK), sol-gel transition point (about 48 °C; 10 °C higher than that of AK), and gel hardness (about 2300 g; 450 g higher than AK). Moreover, the AKX-16% composite showed lower crystallinity and enhanced hydrogen bonding and tensile strength (74 MPa) resulting from gel dehydration. Additionally, increasing the XG content showed a negligible effect on the morphology of the composite matrix, suggesting the excellent compatibility between these different polysaccharides. [Display omitted] • Xanthan inclusion (16% for instance) strengthened chain entanglements of agar/KGM system. • Xanthan inclusion increased the zero-shear viscosity of agar/KGM-based system. • Xanthan inclusion increased the sol-gel transition point of agar/KGM-based system. • Xanthan inclusion increased the gel hardness of agar/KGM-based system. • Xanthan inclusion enhanced the tensile strength of agar/KGM-based composite. [ABSTRACT FROM AUTHOR]

The practical features (e.g., sol-gel, mechanical and hydrophobic) of biopolymer systems are crucial for their materials applications. This work reveals how polyvinyl alcohol (PVA) inclusion affects the practical features of agar/konjac glucomannan (KGM) system. From rheological analysis, incorporating PVA (especially 6%) enhanced the chain entanglements of resulted ternary solution (A 70 K 24 P 6) with stabilized sol-gel transition point. Such effect not only increased the zero-shear viscosity (ca. 1.5 times that of agar/KGM counterpart) and structural recovery degree of A 70 K 24 P 6 solution, but also caused reduced crystallites and simultaneously increased tensile strength, elongation at break and hydrophobicity for A 70 K 24 P 6 film from solution dehydration. This ternary film exhibited a tensile strength of ca. 105 MPa, an elongation at break of ca. 20%, and a water contact angle of ca. 97.6°. Additionally, incorporating PVA almost unaffected the morphology of film fracture surface. These results are valuable for the design of agar/KGM systems with improved practical features. [ABSTRACT FROM AUTHOR]

With abundant renewable resources and good biodegradability, bio-based aerogels are considered as promising insulating materials for replacing the conventional petroleum-based foam. In this study, konjac glucomannan (KGM)-based aerogels were prepared as thermal insulation materials via a convenient sol–gel and freeze-drying progress with different content of plant polysaccharides, proteins, and wheat straw. The morphology, thermal conductivity, and flame retardancy of KGM-based aerogels were determined. The KGM-based aerogels showed a uniform three-dimensional porous microstructure. The addition of wheat straw could significantly reduce the pore size of aerogels due to its special multi-cavity structure. KGM-based aerogels showed low densities (0.0234–0.0559 g/cm−3), low thermal conductivities (0.04573–0.05127 W/mK), low peak heat release rate (PHRR, 46.7–165.5 W/g), and low total heat release (THR, 5.7–16.2 kJ/g). Compared to the conventional expanded polystyrene (EPS) and polyurethane (PU) foam, the maximum limiting oxygen index (LOI) of KGM-based aerogels increased by 24.09% and 47.59%, the lowest PHRR decreased by 79.37% and 94.26%, and the lowest THR decreased by 76.54% and 89.25%, respectively. The results demonstrated that the KGM-based aerogels had better performance on flame retardancy than PU and EPS, indicating high potential applications as heat insulation in the green advanced engineering field. [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]

Although gelatin-based composite gels have been widely used in the food and pharmaceutical industries, further research is needed to improve gel strength. This work reported the microstructure and gel properties of gelatin-based composite gels containing different contents of κ-carrageenan (CGN) or konjac glucomannan (KGM). The rheological and textural results revealed that the gelling temperature, melting temperature, strength (from 1.68 to 4.13 times), toughness, and chewiness of the composite gel were positively correlated with the addition of CGN. The microscopy and infrared spectroscopy showed that gelatin and CGN molecules could be clustered in helices by electrostatic interactions and hydrogen bonding to form excellent gel networks with outstanding gelation properties. However, gelatin and KGM could either be compatible with or separated from each other. At a low KGM content, the gelatin-based composite gel was porous and had a dense gel structure. When the KGM content was 0.3%, the composite gel showed greater ordering degree. Thus, the addition of the proper amount of CGN to gelatin led to composite gels with better strength, toughness, and chewiness, whereas the addition of KGM generated gels being easy to chew and swallow. [Display omitted] • Addition of κ-carrageenan enhanced strength, toughness, and chewiness of gelatin-based gel. • Addition of κ-carrageenan promoted gel formation and suppressed gel disruption. • Phase separation occurred for gelatin-based gel with >0.3% konjac glucomannan. [ABSTRACT FROM AUTHOR]

The synergistic interaction gels (SIGs) can be created by blending konjac glucomannan (KGM) and κ-carrageenan, and have been applied to modify and improve the rheological and texture properties of food system. However, the assembly behaviors between them are still unclear. This work revealed that the presence of KGM promoted phase transition of nearby κ-carrageenan molecules probably by contributing to entropy increment. Subsequently, the rest of κ-carrageenan transformed into helical structure, assembled into a series of laterally arranged trigonal units and formed a three-dimensional network. In KGM/κ-carrageenan SIGs, the size of high density domains (Ξ) in aggregates and the distance of these high density domains (ξ) were narrowed firstly and then enlarged as increasing of KGM content. These nano-scale structure features were responsible for the relative higher gel strength for KGM/κ-carrageenan SIGs with proportion ratios of 1:9 (K1C9) and 3:7 (K3C7). This study serves to facilitate the design and production of SIGs with the requisite performance characteristics. [ABSTRACT FROM AUTHOR]

Synergistic interaction gels (SIGs) formed by mixing konjac glucomannan (KGM) and xanthan at an appropriate ratio have gained increased interest due to its inherent versatility. However, their mechanical properties were not high enough to meet the needs of practical applications. This work demonstrated that freeze-thaw treatment (FT) significantly improved their mechanical properties, and the underlying mechanisms were proposed. Relative lower frozen temperature (−40 °C or −80 °C) and more freeze-thaw cycles reduced the pore size, decreased the average size of orderings (crystalline structure) and increased the ordering content (at −40 °C or under third cycle at −80 °C, except for KGM/xanthan SIGs with a ratio of KGM to xanthan at 2:8) for KGM/xanthan SIGs. Those undoubtedly increased the crosslinking density and improved the gel structure, which was responsible for the increment of G ' (at 25–30 °C) and gel hardness, and reduction of water holding capacity. Freeze-thaw treatment with −15 °C did not increase the ordering contents and gel hardness, but enhanced the G ' (at 25–30 °C). It is possible that freezing at −15 °C enhanced gel structure rigidity by increasing the molecular entanglement via squeezing of ice crystals and rearrangement of molecular chains. Those results are helpful to rational design and production of KGM/xanthan SIGs with physical methods. [Display omitted] • Freeze-thaw treatment improved mechanical properties of KGM/xanthan gels. • Pore structure was altered significantly after freeze-thaw treatment. • Frozen at −40 or −80 °C decreased average size of ordering structure. • Treatment of two/three freeze-thaw cycles decreased average size of ordering structure. • Frozen at −40 or −80 °C (three cycles) increased contents of nano-scale ordering structure. [ABSTRACT FROM AUTHOR]

Core-shell structural capsules can encapsulate various food ingredients (e.g., nutrients), thus being highly potential for the design of many food products. This work reports how the gum (xanthan, locust bean or gellan) inclusion tailors the practical features of agar/konjac glucomannan (KGM) system for fabricating the core-shell structural capsules. The rheological and textural analyses revealed that xanthan gum inclusion could simultaneously increase the sol-gel transition point and gel strength (ca. 1.6 times higher) of agar/KGM system. The composite gels were dehydrated to generate shell materials. The materials including xanthan or locust bean gum showed stronger chain interactions than did that including gellan gum, accompanied by weakened crystalline features for the different shell materials. Again, compared to the agar/KGM counterpart, the shell materials including xanthan gum could display a similar tensile strength (close to 50 MPa) but an evidently increased elongation at break (ca. 2.5 times higher). Then, these agar/KGM based systems were used to prepare core-shell structural capsules. The capsules based on agar/KGM/xanthan gum materials exhibited the highest roundness and breaking stress. Regarding this, the increased sol-gel point reduced the time required for droplet hardening (to generate core-shell gel balls); such fact, together with the higher gel strength, weakened the deformation of gel balls and thus increased the roundness and breaking stress of capsules (resulting from drying of gel balls). [Display omitted] • Adding xanthan gum increased sol-gel point of agar/konjac glucomannan (KGM) system. • Adding xanthan gum increased gel strength of agar/KGM based system. • Adding xanthan gum increased elongation at break of agar/KGM based shell materials. • Adding xanthan gum increased roundness of agar/KGM based core-shell capsules. • Adding xanthan gum increased breaking stress of agar/KGM based core-shell capsules. [ABSTRACT FROM AUTHOR]