Recent advances in the understanding of heat set gelling polysaccharides

Potential for curdlan recovery from aerobic granular sludge wastewater treatment systems - A review

The aerobic granular sludge (AGS) biotechnology has been explored for wastewater treatment for over two decades. AGS is gaining increased interest due to its enhanced treatment performance ability and the potential for resource recovery from AGS-based wastewater treatment systems. Resource recovery from AGS is a promising approach to sustainable wastewater treatment and attaining a circular economy in the wastewater management industry. Currently, research is at an advanced stage on recovering value-added resources such as phosphorus, polyhydroxyalkanoates, alginate-like exopolysaccharides, and tryptophan from waste aerobic granules. Recently, other value-added resources, including curdlan, have been identified in the aerobic granule matrix, and this may increase the sustainability of biotechnology in the wastewater industry. This paper provides an overview of AGS resource recovery potential. In particular, the potential for enhanced curdlan biosynthesis in the granule matrix and its recovery from AGS wastewater treatment systems is outlined.

Advances in the construction and application of konjac glucomannan-based delivery systems

Konjac glucomannan (KGM) has been widely used to deliver bioactive components due to its naturalness, non-toxicity, excellent biodegradability, biocompatibility, and other characteristics. This review presents an overview of konjac glucomannan as a matrix, and the types of konjac glucomannan-based delivery systems (such as hydrogels, food packaging films, microencapsulation, emulsions, nanomicelles) and their construction methods are introduced in detail. Furthermore, taking polyphenol compounds, probiotics, flavor substances, fatty acids, and other components as representatives, the applied research progress of konjac glucomannan-based delivery systems in food are summarized. Finally, the prospects for research directions in konjac glucomannan-based delivery systems are examined, thereby providing a theoretical basis for expanding the application of konjac glucomannan in other industries, such as food and medicine.

The alleviative effect of curdlan on the quality deterioration of konjac glucomannan thermo-irreversible gels after commercial sterilization at 121 °C

This work employed different curdlan concentrations (0.00 %, 1.00 %, 1.50 %, 2.00 %, and 2.50 %) to alleviate the quality degradation of konjac glucomannan (KGM) gels after commercial sterilization at 121 °C for 15 min. The results showed that all levels of curdlan could retard the deterioration of KGM gels, with the best effect at 2.00 %. After commercial sterilization, incorporating curdlan into KGM gels greatly reduced the Tan σ (G"/ G'), total relaxation time and half-free water from 0.52, 89.85 ms and 98.26 % to 0.27, 38.48 ms and 21.42 %, respectively. Moreover, the addition of curdlan imparted a better texture to KGM gels, as reflected in the increase of hardness, springiness, water-holding capacity and whiteness value from 1400.85 g, 0.42, 87.92 % and 33.33 to 3461.68 g, 0.80, 96.50 % and 49.27, respectively. Furthermore, SEM images revealed that curdlan endowed KGM gels with a tighter structure and smaller pores, and the pore size distribution was reduced from 113.46 μm to17.91 μm, indicating a stronger interaction among molecules, as evidenced by XRD and FTIR results. KGM gels with curdlan possessed less proportion of complete crystallites and crystalline region. These findings suggested that curdlan can be the potently protectant for improving the quality of commercially sterilized KGM gel-based products.

Konjac glucomannan/xanthan gum/sodium alginate composite hydrogel simulates fascial tissue by pre-stretching and moisture regulation

Improving the mechanical strength and creating an anisotropic structure of edible macromolecular hydrogels is crucial to accurately simulate the texture of connective tissues. In this study, konjac glucomannan (KGM), xanthan gum (XG), and sodium alginate (SA) were used to construct hydrogels, and the effects of different pre-stretching degrees and moisture control on the composite gels were investigated. The results of the mechanical property tests and microstructure tests indicate that pre-stretching and moisture control can significantly enhance the strength of the gels and induce anisotropic structures. In addition, the feasibility of the composite gel structure in simulating brisket fascia was investigated, and it was concluded that 1.5 × -DR samples were most suitable for simulating connective tissue. This study provides compelling evidence for the potential of macromolecular hydrogels in simulating connective tissue and provides theoretical guidance for regulating gel texture.

A Comprehensive Review of Food Hydrogels: Principles, Formation Mechanisms, Microstructure, and Its Applications

Food hydrogels are effective materials of great interest to scientists because they are safe and beneficial to the environment. Hydrogels are widely used in the food industry due to their three-dimensional crosslinked networks. They have also attracted a considerable amount of attention because they can be used in many different ways in the food industry, for example, as fat replacers, target delivery vehicles, encapsulating agents, etc. Gels-particularly proteins and polysaccharides-have attracted the attention of food scientists due to their excellent biocompatibility, biodegradability, nutritional properties, and edibility. Thus, this review is focused on the nutritional importance, microstructure, mechanical characteristics, and food hydrogel applications of gels. This review also focuses on the structural configuration of hydrogels, which implies future potential applications in the food industry. The findings of this review confirm the application of different plant- and animal-based polysaccharide and protein sources as gelling agents. Gel network structure is improved by incorporating polysaccharides for encapsulation of bioactive compounds. Different hydrogel-based formulations are widely used for the encapsulation of bioactive compounds, food texture perception, risk monitoring, and food packaging applications.

Recent insights into polysaccharide-based hydrogels and their potential applications in food sector: A review

Hydrogels are ideal for various food applications because of their softness, elasticity, absorbent nature, flexibility, and hygroscopic nature. Polysaccharide hydrogels are particularly suitable because of the hydrophilic nature, their food compatibility, and their non-immunogenic character. Such hydrogels offer a wide range of successful applications such as food preservation, pharmaceuticals, agriculture, and food packaging. Additionally, polysaccharide hydrogels have proven to play a significant role in the formulation of food flavor carrier systems, thus diversifying the horizons of newer developments in food processing sector. Polysaccharide hydrogels are comprised of natural polymers such as alginate, chitosan, starch, pectin and hyaluronic acid when crosslinked physically or chemically. Hydrogels with interchangeable, antimicrobial and barrier properties are referred to as smart hydrogels. This review brings together the recent and relevant polysaccharide research in these polysaccharide hydrogel applications areas and seeks to point the way forward for future research and interventions. Applications in carrying out the process of flavor carrier system directly through their incorporation in food matrices, broadening the domain for food application innovations. The classification and important features of polysaccharide-based hydrogels in food processing are the topics of the current review study.

An innovative konjac glucomannan/κ-carrageenan mixed tensile gel

BACKGROUND

Konjac glucomannan (KGM) showed a synergistic interaction with κ-carrageenan (CAR), which led to the formation of a promising compound hydrocolloid gel in the food field (such as jelly). Nevertheless, the mixed gels formed by adding KGM to CAR still displayed defects in gel strength and syneresis, and would hardly meet the quality requirements of some gel foods. However, deacetylated KGM and maltodextrin (MD) have always been used in gel foods and affect their viscosity and rheological properties.

RESULTS

In our paper, different amounts of MD were first used to alter the textural properties, and the results showed that both tensile strength and elongation exhibited first an increasing and then a decreasing trend with the increasing MD proportion and achieved a maximum at a final maltodextrin proportion of 4 g kg^-1 in the KGM/CAR/MD system. Based on the above results, we further explored the effects of deacetylation degree of KGM on the gel properties of mixed gel system. The results revealed that, compared to the native KGM, the partial deacetylated KGM was capable of significantly improving the tensile strength and elongation of KGM/CAR mixed gel.

CONCLUSION

Our study found that the appropriate addition of MD (0.4%) and DKGM were able to alter the tensile properties of KGM/CAR mixed gel, with potential to meet the needs of consumers and further design innovative tensile gel products in the soft gel industry. © 2021 Society of Chemical Industry.

A freeze-thawing method applied to the fabrication of 3-d curdlan/polyvinyl alcohol hydrogels as scaffolds for cell culture

In this work, an innovative composite hydrogel composed of curdlan (CD)/polyvinyl alcohol (PVA) hydrogels with a 3-d network structure was successfully prepared by freeze-thaw processing. The presence of interactions, changes in crystallinity, and thermal behaviour were investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and thermogravimetry (TGA and DTG), respectively. The morphology of the hydrogels was investigated by scanning electron microscopy (SEM). With the increase of PVA concentration, the composite hydrogel had a greater mechanical strength while remaining remarkably ductile as evinced by tensile test results. PVA content affects the swelling and water retention of CD/PVA hydrogels. The results of CCK-8 assay showed that CD/PVA hydrogels have no cytotoxic effect on the mouse fibroblast L929 cells. The AO/EB double-staining experiment further proved that the cells in the composite hydrogels had good cytocompatibility. The porous biohydrogels developed in the present work can provide an ideal cell growth environment as a scaffold. CD/PVA hydrogels highlight the value of this system for cell adhesion and proliferation, and further soft tissue engineering application.

DSC and TMA Studies of Polysaccharide Physical Hydrogels

Various kinds of polysaccharides found in a wide variety of plants, bacteria, crustaceans and insects form hydrogels via physical aggregation in aqueous media. The major mass of hydrogels is water filled, ca. 95 - 99.5%, in a network structure, although the solid shape of the gel is maintained. In this paper, firstly the wide range of gelation mechanisms are briefly described, and then the thermal analysis of representative gel-forming polysaccharides, such as carrageenan, alginate, galactomannan, and pectin, is introduced. By differential scanning calorimetry (DSC), gel-sol and the sol-gel transition temperature of thermoreversible hydrogels are measured and phase diagram is established. It is suggested that binary systems showing sinusoidal gel-sol-gel transition are capable of being assembled. By thermomechanical analysis (TMA), the dynamic modulus (E') at around 1 × 104 Pa of thermo-irreversible hydrogels was obtained using a sample holder designed to measure the viscoelastic properties in water. Reliable coordination is shown between the results obtained by DSC and TMA. In this review, the current research and several topics on concerning the thermal properties of polysaccharide physical hydrogels are introduced.

Synthesis and characterization of novel tamarind gum and rice bran oil-based emulgels for the ocular delivery of antibiotics

In this study, we developed tamarind gum (TG) and rice bran oil (RBO)-based emulgels. The control formulation (TR0), did not contain RBO. The emulgels were named as TR1, TR2, TR3, and TR4, which contained 5% (w/w), 10% (w/w), 15% (w/w), and 20% (w/w/) of RBO, respectively. The microscopic studies showed that the emulgels were biphasic in nature. FTIR spectroscopy revealed the reduction in the hydrogen bonding with an increase in the RBO content. Impedance profiles suggested that the resistive component of the emulgels was increased as the RBO content was increased. The thermal analysis suggested that the addition of RBO reduced the water holding capacity of the emulgels. Stress relaxation studies revealed that the fluidic component was considerably higher in TG/RBO-based emulgels as compared to TR0. In vitro release study of the model drug (ciprofloxacin HCl; a hydrochloride salt of ciprofloxacin) suggested a significantly lower release from the emulgel matrices (TR1-TR4) in comparison to TR0. However, ex vivo corneal permeation of the drug increased with an increase in the RBO content. Since the emulgels were able to improve the corneal permeation of the model drug, the emulgels can be explored to deliver drugs to the internal structures of the eye.

Impact of heating and drying temperatures on the properties of konjac glucomannan/curdlan blend films

The impact of preparation conditions including heating temperature (from 60 °C to 90 °C) and drying temperatures (from 25 °C to 90 °C) on the properties of pure curdlan film and konjac glucomannan (KGM) and curdlan blend films were analyzed. Microstructure analysis indicated the KGM addition could significantly improve the relatively poor film-forming property of curdlan. FTIR and X-ray analysis showed that at high heating temperature 90 °C, molecular interaction might be enhanced in the films due to the stretched structure of curdlan and dissociation of curdlan bundles or triple-helix structure. This was supported by the changes in the mechanical property, surface hydrophobicity, moisture barrier, and moisture tolerance property. The impacts of drying temperature were some different for the curdlan film and KGM/curdlan blend film, and were explained from the molecular hydrophilicity-hydrophobicity, compactness of the films, curdlan conformation, and molecular interaction. This work guided biodegradable film production especially with curdlan added.

Ultrasonic Degradation of Konjac Glucomannan and the Effect of Freezing Combined with Alkali Treatment on Their Rheological Profiles

The effect of freezing combined with alkali treatment on physicochemical property of konjac glucomannan (KGM) with different molecular weight was investigated in this work. The properties and structure of degraded KGM was characterized by means of intrinsic viscosity measurement, atomic force microscope (AFM) and Fourier transformation infrared (FT-IR). The results suggested that the intrinsic viscosity of KGM solution gradually decreased during the ultrasonic treatment. The AFM observation indicated that KGM with lower viscosity average molecular weight had smaller height and lateral diameter of molecules. The main repeating units of the KGM chain could not be destroyed no matter how long the KGM was sonicated. Rheometrical studies revealed that with increasing alkali concentration from 0% to 0.36%, both viscosities and shear stress of deacetylated konjac glucomannan (Da-KGM) system were increased and moduli G' were substantially higher in either freezing or unfreezing samples. Da-KGM system performed a solid-like behavior (G' > G'') along the frequency range after freezing treatment. With increasing sonication time, both viscosity and shear stress of unfreezing samples were decreased while had an inverse effect for freezing treated samples. The modulus G' and G'' declined for unfreezing samples but rise significantly for freezing treated samples with increase of sonication time.

Enhancement of the Textural and Gel Properties of Frankfurters by Adding Thermo-reversible or Thermo-irreversible Curdlan Gels

The influence of different addition levels (0.1% to 0.5%) of thermo-reversible curdlan gels (TRC) and thermo-irreversible curdlan gels (TIRC) on the physicochemical and textural characteristics of frankfurters, as well as dynamic rheological properties of meat batters, was investigated. Increased percentages of TRC and TIRC were associated with lower cooking loss and quicker relaxation times, as well as superior emulsion stability, and higher L^* -values and b^* -values of frankfurters (P < 0.05). Moreover, with equal curdlan concentrations from 0.3% to 0.5%, TRC showed higher hardness and chewiness values than those with added TIRC (P < 0.05), but the gumminess, springiness, and resilience values were almost the same between each treatment (P > 0.05). The textural profile results were in strong agreement with the rheological data. Principal component analysis revealed that certain quality attributes were affected differently by the inclusion levels of TRC and TIRC. Additionally, the distinctive mechanism of the formation of the complex meat protein network by TRC or TIRC was also clarified and verified via scanning electron microscopy analysis. Further studies will investigate the molecular interactions of meat proteins with these two types of curdlan gels as a function of addition levels. PRACTICAL APPLICATION: Curdlan can form two different types of gels mainly depending on heating temperature, designated as thermo-reversible curdlan gels (TRC) and thermo-irreversible curdlan gels (TIRC), respectively. The addition of these two gels could improve the textural and gel properties of frankfurters, as well as improve the rheological profiles of meat batters. Each gel type invokes a different mechanism of influence on the formation of the complex meat protein network. Results indicate that TRC (mainly as an effective gelling agent) and TIRC (mainly as a potential fat-mimetic) can provide distinctive frankfurter formulations catered to the requirements preferred by different consumers.

In situ observation of gelation of methylcellulose aqueous solution with viscosity measuring instrument in the diamond anvil cell

Gelation of methylcellulose aqueous solution was investigated by a high-pressure viscosity measurement device which consisted of diamond anvil cell, microscope and CCD. And the temperature and pressure dependence of the viscosity of methylcellulose aqueous solution was measured utilizing a rolling-ball technique. The results showed that sol-gel thermal transition of methylcellulose solution occurred at the temperature of 53 °C under atmospheric pressure. Upon compression, it was indicated that the viscosity showed a dramatic change in the vicinity of the pressure of 500 MPa. Parabolic phase diagram of methylcellulose aqueous solution was constructed, and it showed that the melting point was an increasing function of pressure at the first stage and an decreasing function of pressure at the final stage. The mechanism of sol-gel transformation of methylcellulose aqueous solutions was also discussed, it might be assumed that both hydrogen and hydrophobic bonds were involved with the gel formation in the case of methylcellulose aqueous solution.

Effective Immobilization of Agrobacterium sp. IFO 13140 Cells in Loofa Sponge for Curdlan Biosynthesis

Curdlan production by Agrobacterium sp. IFO13140 immobilized on loofa sponge, alginate and loofa sponge with alginate was investigated. There was no statistically-significant difference in curdlan production when the microorganism was immobilized in different matrices. The loofa sponge was chosen because of its practical application and economy and because it provides a high stability through its continued use. The best conditions for immobilization on loofa sponge were 50 mg of cell, 200 rpm and 72 h of incubation, which provided a curdlan production 1.50-times higher than that obtained by free cells. The higher volumetric productivity was achieved by immobilized cells (0.09 g/L/h) at 150 rpm. The operating stability was evaluated, and until the fourth cycle, immobilized cells retained 87.40% of the production of the first cycle. The immobilized cells remained active after 300 days of storage at 4 °C. The results of this study demonstrate success in immobilizing cells for curdlan biosynthesis, making the process potentially suitable for industrial scale-up. Additional studies may show a possible contribution to the reduction of operating costs.

Blend film based on fish gelatine/curdlan for packaging applications: spectral, microstructural and thermal characteristics

Novel biodegradable and thermostable FG/CL (8 : 2) blend film was fabricated and characterised for packaging applications.