Preparation of okara cellulose hydrogels using ionic liquids: Structure, properties, and performance

Fabrication of composite hydrogels by sonication-assisted assembly of okara cellulose nanofibers and chitosan: structure and properties

BACKGROUND

Okara cellulose is a highly abundant, green, sustainable, and biodegradable polymer with many potential industrial applications. In this study, we fabricated composite hydrogels with okara cellulose nanofibers (CNFs) and chitosan (CH) by hydrating, sonicating, and heating them at 100 °C for 30 min, and then induced their assembly by cooling. The effects of okara CNF (with and without 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) oxidation) and CH concentration on the structure and properties of the hydrogels was examined, including their microstructure, surface properties, rheological properties, and thermal stability.

RESULTS

Our results indicate that there was an electrostatic attraction between the anionic okara CNF and cationic CH, which facilitated hydrogel formation. The surface, textural, rheological, and thermal stability properties were better for the composite hydrogels than for the single CH ones, as well as for the CNF that had undergone TEMPO oxidation. For the TC-CH hydrogels, the contact angle was 39.5°, the interfacial tension was 69.1 mN m-1 , and the surface tension was 1.44 mN m-1 .

CONCLUSION

In this study, the novel hydrogels developed may be useful as a soft material in a range of applications in foods, supplements, health care products, cosmetics, and drugs. © 2023 Society of Chemical Industry.

Enhancing the Gelation Behavior of Transglutaminase-Induced Soy Protein Isolate(SPI) through Ultrasound-Assisted Extraction

Gelation, as an important functional property of soy protein isolate (SPI), can be improved by some green technologies in food manufacturing, including ultrasound, ultrahigh pressure and microwave treatments. This work investigated the effect of an alkaline solubilisation step in SPI extraction combined with sonication on protein properties. The TGase-induced gel of the modified SPI was prepared to explore the effect of ultrasound on gel properties, including structures, strength, water-holding capacity and rheological properties. Additionally, the differences between traditional ultrasound modification of SPI and current modification methods were analyzed. The results showed that the ultrasonication-assisted extraction method could result in a significant increase in extraction rate from 24.68% to 42.25%. Moreover, ultrasound-assisted modification of SPI gels induced with transglutaminase (TGase) exhibited significant improvement in mechanical properties, such as texture, water-holding capacity and rheological properties, In particular, SPI extracted at 400 W ultrasound intensity for 180 s showed the best overall performance in terms of gel properties. Our method efficiently uniformizes gel structure, enhancing mechanical properties compared to conventional ultrasound methods, which reduced energy consumption and costs. These findings provide insights into the production of high-gelation SPI in food manufacturing.

The three-dimensional culture of L929 and C2C12 cells based on SPI-SA interpenetrating network hydrogel scaffold with excellent mechanical properties

Cell-cultured meat, which is obtained by adsorbing cells on the three-dimensional scaffold, is considered a potential solution to animal welfare issues. Edible and safe cell-cultured meat scaffolds are a key part of its research. Soy protein isolate (SPI) hydrogel has a three-dimensional network structure and has been studied for L929 cell culture because of its non-toxicity and biocompatibility. However, the toughness and mechanical properties of SPI hydrogel are not enough to bear the requirements of cell cultivation. In this paper, sodium alginate (SA) was added to SPI hydrogel, and the interpenetrating network (IPN) technology was used to construct SPI-SA IPN hydrogel by transglutaminase and Ca2+ double crosslinking method. SPI-SA IPN hydrogel has excellent mechanical properties, structural stability and biodegradable performance than SPI hydrogel. The bio-compatibility and degradability of L929 and C2C12 cells on SPI-SA IPN hydrogel were studied by cytotoxicity, trypan blue and living/dead cell staining, and the growth law of the hydrogel as a scaffold for cell culture was analyzed. The results showed that L929/C2C12 cells can proliferate normally and adhere in hydrogel and have good bio-compatibility. L929 cells with size about 20-50 µm have better adhesion and growth abilities on SPI-SA IPN hydrogel than C2C12 cells with 100-300 µm. Therefore, the SPI-SA IPN hydrogel is non-toxic and supports the growth of cells in the pores of the material. This study provides a reference for the application of SPI-SA IPN hydrogels in vitro cell growth.

How does ultrasound-assisted ionic liquid treatment affect protein? A comprehensive review of their potential mechanisms, safety evaluation, and physicochemical and functional properties

Proteins are essential to human health with enormous food applications. Despite their advantages, plant and animal proteins often exhibit limited molecular flexibility and poor solubility due to hydrogen bonds, hydrophobic interactions, and ionic interactions within their molecular structures. Thus, there is an urgent need to modify the rigid structure of proteins to enhance their stability and functional properties. Ultrasound-assisted ionic liquid (UA-IL) treatment for developing compound modification and producing proteins with excellent functional properties has received interest. However, no review specifically addresses the interactions between UA-ILs and proteins. Hence, this review focused on recent research advancements concerning the effects and potential reaction mechanisms of UA-ILs on the physicochemical properties (including particle size; primary, secondary, and tertiary structure; and surface morphology) as well as the functionality (such as solubility, emulsifying properties, and foaming ability) of proteins. Moreover, the safety evaluation of modified proteins was also discussed from various perspectives, such as acute and chronic toxicity, genotoxicity, cytotoxicity, and environmental and microbial toxicity. This review demonstrated that UA-IL treatment-induced protein structural changes significantly impact the functional characteristics of proteins. This treatment approach efficiently promotes protein structure stretching and spatial rearrangement through cavitation, thermal effects, and ionic interactions. As a result, the functional properties of modified proteins exhibited an obvious enhancement, thereby bringing more opportunities to utilize modified protein products in the food industry. Potential future directions for protein modification using UA-ILs were also proposed.

Cellulose Dissolution, Modification, and the Derived Hydrogel: A Review

The cellulose-based hydrogel has occupied a pivotal position in almost all walks of life. However, the native cellulose can not be directly used for preparing hydrogel due to the complex non-covalent interactions. Some literature has discussed the dissolution and modification of cellulose but has yet to address the influence of the pretreatment on the as-prepared hydrogels. Firstly, the "touching" of cellulose by derived and non-derived solvents was introduced, namely, the dissolution of cellulose. Secondly, the "conversion" of functional groups on the cellulose surface by special routes, which is the modification of cellulose. The above-mentioned two parts were intended to explain the changes in physicochemical properties of cellulose by these routes and their influences on the subsequent hydrogel preparation. Finally, the "reinforcement" of cellulose-based hydrogels by physical and chemical techniques was summarized, viz., improving the mechanical properties of cellulose-based hydrogels and the changes in the multi-level structure of the interior of cellulose-based hydrogels.

Eucalyptus bleached kraft pulp-ionic liquid inks for 3D printing of ionogels and hydrogels

3D printing has been recently recognized as one of the most promising technologies due to the multiple options to fabricate cost-effective and customizable objects. However, the necessity to substitute fossil fuels as raw materials is increasing the research on bio-based inks with recyclable and eco-friendly properties. In this work, we formulated inks for the 3D printing of ionogels and hydrogels with bleached kraft pulp dissolved in [Emim][DMP] at different concentrations (1-4 wt%). We explored each ink's rheological properties and printability and compared the printability parameters with a commercial ink. The rheological results showed that the 3 % and 4 % cellulose-ionic liquid inks exhibited the best properties. Both had values of damping factor between 0.4 and 0.7 and values of yield stress between 1900 and 2500 Pa. Analyzing the printability, the 4 wt% ink was selected as the most promising because the printed ionogels and the hydrogels had the best print resolution and fidelity, similar to the reference ink. After printing, ionogels and hydrogels had values of the elastic modulus (G') between 10³ and 10⁴ Pa, and the ionogels are recyclables. Altogether, these 3D printed cellulose ionogels and hydrogels may have an opportunity in the electrochemical and medical fields, respectively.

Gel Properties and Structural Characteristics of Composite Gels of Soy Protein Isolate and Silver Carp Protein

Problems with silver carp protein (SCP) include a strong fishy odor, low gel strength of SCP surimi, and susceptibility to gel degradation. The objective of this study was to improve the gel quality of SCP. The effects of the addition of native soy protein isolate (SPI) and SPI subjected to papain-restricted hydrolysis on the gel characteristics and structural features of SCP were studied. The β-sheet structures in SPI increased after papain treatment. SPI treated with papain was crosslinked with SCP using glutamine transaminase (TG) to form a composite gel. Compared with the control, the addition of modified SPI increased the hardness, springiness, chewiness, cohesiveness, and water-holding capacity (WHC) of the protein gel (p < 0.05). In particular, the effects were most significant when the degree of SPI hydrolysis (DH) was 0.5% (i.e., gel sample M-2). The molecular force results demonstrated that hydrogen bonding, disulfide bonding, and hydrophobic association are important molecular forces in gel formation. The addition of the modified SPI increases the number of hydrogen bonds and the disulfide bonds. Scanning electron microscopy (SEM) analysis showed that the papain modifications allowed the formation of a composite gel with a complex, continuous, and uniform gel structure. However, the control of the DH is important as additional enzymatic hydrolysis of SPI decreased TG crosslinking. Overall, modified SPI has the potential to improve SCP gel texture and WHC.

Effect of High-Intensity Ultrasound Pretreatment on the Properties of the Transglutaminase (TGase)-Induced β-Conglycinin (7S) Gel

In this study, we investigated the effects of different high-intensity ultrasound (HIU) pretreatment times (0-60 min) on the structure of β-conglycinin (7S) and the structural and functional properties of 7S gels induced by transglutaminase (TGase). Analysis of 7S conformation revealed that 30 min HIU pretreatment significantly induced the unfolding of the 7S structure, with the smallest particle size (97.59 nm), the highest surface hydrophobicity (51.42), and the lowering and raising of the content of the α-helix and β-sheet, respectively. Gel solubility showed that HIU facilitated the formation of ε-(γ-glutamyl)lysine isopeptide bonds, which maintain the stability and integrity of the gel network. The SEM revealed that the three-dimensional network structure of the gel at 30 min exhibited filamentous and homogeneous properties. Among them, the gel strength and water-holding capacity were approximately 1.54 and 1.23 times higher than those of the untreated 7S gels, respectively. The 7S gel obtained the highest thermal denaturation temperature (89.39 °C), G', and G″, and the lowest tan δ. Correlation analysis demonstrated that the gel functional properties were negatively correlated with particle size and the α-helix, while positively with Ho and β-sheet. By contrast, gels without sonication or with excessive pretreatment showed a large pore size and inhomogeneous gel network, and poor properties. These results will provide a theoretical basis for the optimization of HIU pretreatment conditions during TGase-induced 7S gel formation, to improve gelling properties.

Cellulose-Based Metallogels-Part 1: Raw Materials and Preparation

Metallogels are a class of materials produced by the complexation of polymer gels with metal ions that can form coordination bonds with the functional groups of the gel. Hydrogels with metal phases attract special attention due to the numerous possibilities for functionalization. Cellulose is preferable for the production of hydrogels from economic, ecological, physical, chemical, and biological points of view since it is inexpensive, renewable, versatile, non-toxic, reveals high mechanical and thermal stability, has a porous structure, an imposing number of reactive OH groups, and good biocompatibility. Due to the poor solubility of natural cellulose, the hydrogels are commonly produced from cellulose derivatives that require multiple chemical manipulations. However, there is a number of techniques of hydrogel preparation via dissolution and regeneration of non-derivatized cellulose of various origins. Thus, hydrogels can be produced from plant-derived cellulose, lignocellulose and cellulose wastes, including agricultural, food and paper wastes. The advantages and limitations of using solvents are discussed in this review with regard to the possibility of industrial scaling up. Metallogels are often formed on the basis of ready-made hydrogels, which is why the choice of an adequate solvent is important for obtaining desirable results. The methods of the preparation of cellulose metallogels with d-transition metals in the present state of the art are reviewed.

Locust bean gum provides excellent mechanical and release attributes to soy protein-based natural hydrogels

The current study concentrated on designing soy protein (SP)-based natural hydrogels in the presence of locust bean gum (LBG). For this, the gums were recovered from the kernel of the relevant plant and incorporated into SP gel models. Three more hydrogels were fabricated using commercial carbohydrates (gum Arabic (GA), maltodextrin (MD), and pectin (PC)) to decipher exactly the ability of LBG in these models. The chemical and morphological structures of the samples were elaborated by FTIR and SEM analyses. The coexistence of protein and carbohydrates led to an enhancement in functional (water holding capacity (WHC), swelling ratio, protein leachability, volumetric gel index (VGI)) and mechanical (textural and rheological behavior) features of natural gels compared to SP alone (control) but the quality of hydrogels was impressed by the carbohydrate type. Hydrogels designed with LBG came to the fore in terms of these attributes. Additionally, these gel models created awareness for phenolic delivery.

Walnut Protein Isolate-κ-Carrageenan Composite Gels Improved with Synergetic Ultrasound-Transglutaminase: Gelation Properties and Structure

Walnut protein is a kind of natural, high-quality plant protein resource. However, its high content of gluten, strong hydrophobicity and poor gelation ability have greatly limited its development and utilization in gel products. It was found in this experiment that ultrasonic power combined with transglutaminase (TGase) had a significant effect on the gel properties of the walnut protein isolate (WNPI)-κ-carrageenan (KC) complex. The results showed that the gel strength of the WNPI-KC complex first increased and then decreased with the increase in ultrasonic power (0-400 W). WNPI-KC composite gel had the best texture properties, rheological properties, water-holding capacity (99.41 ± 0.76%), swelling ratio (2.31 ± 0.29%) and thermal stability (83.22 °C) following 200 W ultrasonic pretreatment. At this time, the gel network was more uniform and much denser, and the water molecules were more tightly bound. Further, 200 W ultrasonic pretreatment could promote the transformation of α-helices to β-folds in protein molecules, improve the fluorescence intensity, increase the content of free sulfhydryl groups and enhance the intermolecular forces. The experimental results could provide technical support for the development of walnut protein gel food.

Characteristics and structure of a soy protein isolate-lutein nanocomplex produced via high-pressure homogenization

BACKGROUND

In recent years, nanocarriers for transporting active substances have attracted attention. This study was to explore the soy protein isolate (SPI) after high-pressure homogenization (HPH) (0, 30, 60, 90 and 120 MPa) as potential lutein carriers.

RESULTS

The load amount (LA) and encapsulation efficiency (EE) of the SPI-lutein nanocomplexes at a homogenization pressure of 60 MPa were the highest (2.32 mg mL^-1 and 92.85%, respectively), and the average particle size and ζ-potential of the SPI-lutein nanocomplexes were 192.1 nm and -30.06 mV, respectively. The DPPH (2,2-diphenyl-1-picrylhydrazyl) and hydroxyl-antioxidant activities of the complex increased from 12.4% and 23.3% to 52.7% and 61.07%, respectively, after the protein was treated with HPH. The surface hydrophobicity of the SPI and the SPI-lutein nanocomplexes increased with increasing homogenization pressure treatment. Fourier transform-infrared spectrophotometry analyses suggested that the homogenization treatments resulted in partial unfolding of the protein molecules, and the addition of lutein can also lead to the change of protein secondary structure. The fluorescence emission of SPI was quenched by lutein through the static quenching mechanism. Fluorescence experiments revealed that SPI and lutein had the strongest binding ability through hydrophobic interaction at a homogenization pressure of 60 MPa.

CONCLUSION

After HPH, the combination of SPI and lutein was beneficial, and the stability of lutein also improved after the combination. This study is conducive to expanding the application of soybean protein in the food industry. © 2022 Society of Chemical Industry.

The measurement of molecular interactions, structure and physical properties of okara cellulose composite hydrogels using different analytical methods

BACKGROUND

Aiming to address the practical problems of a low utilization rate and the serious waste of soybean residue, novel composite hydrogels based on okara cellulose before and after 2,2,6,6-tetramethylpiperidine oxide (TEMPO) oxidation and high polymers of chitosan (CH), carrageenan (CA) or Arabic gum (AG) were prepared by a homogeneous mixture in ionic liquid.

RESULTS

In the present study, composite hydrogels fabricated from okara cellulose and CH, CA or AG were prepared by dissolving them in an ionic liquid, followed by heating (100 °C, 3 h) and then soaking them in a 1:1 water-isopropanol solution. The composite hydrogels prepared from TEMPO oxidation-treated cellulose were physically cross-linked to CH, CA or AG. The results showed that the intramolecular hydrogen bonds in the amorphous regions of the cellulose were disrupted, whereas the intermolecular hydrogen bonds between the biopolymers were increased, which promoted the formation of composite gels with crystalline structures. The TEMPO treatment increased the gel strength. For example, for the cellulose/CA gels, the hardness, fracturability, springiness and cohesiveness values were 5.9-, 4.3-, 2.4- and 3.6-fold higher compared to the non-treated ones, respectively. The composite hydrogels exhibited good thermal stability, swelling properties and mechanical properties. These novel composite polysaccharide-based hydrogels may therefore have great potential in various food and non-food fields.

CONCLUSION

In summary, the addition of polymers (CH, CA or AG) and TEMPO oxidized cellulose was suitable for increasing the swelling, textural properties, thermal stability and rheological properties of hydrogels, which provides new ideas and new methods for the preparation of bio-based composite hydrogels. © 2022 Society of Chemical Industry.

Progress, Challenge and Perspective of Fabricating Cellulose

Cellulose as the most abundant biopolymers on Earth, presents appealing performance in mechanical properties, thermal management, and versatile functionalization. The development of fabrication methods closely relates to enrich its functionality and reduce manufacture cost. However, cellulose is hard to be dissolved by most common solvents or melt due to its recalcitrant property. Herein, the recent progress of fabricating cellulose is summarized. First, the unique hierarchical structure of cellulose is fully investigated and the resulted processability is highlighted in directions of down to nanocellulose, dissolution, and thermoplastic processing. Then, the reported fabrication methods are summarized in three aspects: (1) self-assembly from nano/micro cellulose suspensions, especially the self-assembly of cellulose nanocrystals; (2) dissolution-regeneration-drying, covering spinning and solvent infusion processing; and (3) thermoplastic processing, focusing on analysis of the setup and the morphology changes of the prepared products. In each aspect, the flowchart of the fabrication process, the behind mechanism, fabricated products, and effects of processing parameters are explored. Finally, this review provides a perspective on the further direction of fabricating cellulose, especially the challenges toward mass production of cellulose. This article is protected by copyright. All rights reserved.

Effect of cavitation jets on the physicochemical properties and structural characteristics of the okara protein

The structural andphysicochemical properties of okara protein (OP) subjected to different cavitation jet (CJ) treatment times (0-15 min) were analyzed. In this study, the microstructure and apparent morphology of OP were analyzed by Raman spectrum, fluorescence spectrum, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and atomic force microscopy (AFM). Physicochemical properties, such as emulsion ability (EA), emulsion stability index (ESI), foaming characteristics (FC), foaming stability (FS), and solubility analysis of the OPs, were characterized. Raman spectrum analysis showed that CJ treatment caused increases in the ordered structure of OPs (α-helix, β-sheet, and β-turn), and the disulfide bond g-g-g and g-g-t modes, while it caused a decrease in the t-g-t mode. However, the tertiary structure of OP unfolded and mostly degraded into small subunits because of higher cavitation, shear and temperature effects. AFM observation indicated that CJ resulted in a more uniform distribution of OP. Moreover, changes in the structure of OP significantly affected its functional properties. The results showed that when CJ treatment time was 10 min, the solubility of OP was up to (28.72 ± 1.26)%, the soluble protein content of okara was up to (10.44 ± 0.03) g/100 g, and interface properties were better. In summary, OP has great potential for application in the food area, especially in emulsifying agent and foam system. PRACTICAL APPLICATION: The cavitation jet technology improves the structure and physical and chemical properties of the protein extracted from soybean residue (okara) and provides new ideas for the further development and utilization of soybean residue protein, which may lead to the production of high-value-added functional ingredients from the processing of soybean byproducts.