Double-Network Hydrogels of Corn Fiber Gum and Soy Protein Isolate: Effect of Biopolymer Constituents and pH Values on Textural Properties and Microstructures

Preparation of bovine serum albumin-arabinoxylan cold-set gels by glucono-δ-lactone and salt ions double induction

In order to investigate the effect of glucono-δ-lactone (GDL) and different salt ions (Na+ and Ca2+) induction on the cold-set gels of bovine serum albumin (BSA)-arabinoxylan (AX), the gel properties and structure of BSA-AX cold-set gels were evaluated by analyzing the gel strength, water-holding capacity, thermal properties, and Fourier Transform Infrared (FTIR) spectra. It was shown that the best gel strength (109.15 g) was obtained when the ratio of BSA to AX was 15:1. The addition of 1 % GDL significantly improved the water-holding capacity, gel strength and thermal stability of the cold-set gels (p < 0.05), and the microstructure was smoother. Low concentrations of Na+ (3 mM) and Ca2+ (6 mM) significantly enhanced the hydrophobic interaction and hydrogen bonding between BSA and AX after acid induction, and the Na+-induced formation of a denser microstructure with a higher water-holding capacity (75.51 %). However, the excess salt ions disrupted the stable network structure of the cold-set gels and reduced their thermal stability and crystalline structure. The results of this study contribute to the understanding of the interactions between BSA and AX induced by GDL and salt ions, and provide a basis for designing hydrogels with different properties.

Mechanism on microbial transglutaminase and Tremella fuciformis polysaccharide-mediated modification of lactoferrin: Development of functional food

Lactoferrin (LF) with various biological functions demonstrates great application potential. However, its application was restricted by its poor gelation and instability. The aim of this work was to explore the effect of microbial transglutaminase (MTGase) and Tremella fuciformis polysaccharide (TP) on the functional properties of LF. The formation of a self-supporting LF gel could be induced by MTGase through generating covalent crosslinks between the LF protein molecules. Meanwhile, TP was introduced into the gel system to improve the strength of LF-TP composite gels by enhancing non-covalent interactions such as hydrogen bond and electrostatic interactions during gel formation. Additionally, the LF-TP composite gel exhibited outstanding functional characteristics such as gastrointestinal digestive stability and antioxidant property. This work clarified the mechanism on MTGase and TP-mediated modification of lactoferrin, offered a novel strategy to increase the functional characteristics of LF, and enlarged the application range of LF and TP.

Soybean protein isolate-sodium alginate double network emulsion gels: Mechanism of formation and improved freeze-thaw stability

Soybean protein isolate (SPI) is widely used in the food industry. However, SPI-based emulsion gels tend to aggregate and undergo oiling-off during freeze-thawing. In this study, emulsion gels were prepared by a combination of heat treatment and ionic cross-linking using SPI and sodium alginate (SA) as raw materials. The focus was on exploring the mechanistic effects of the SPI-SA double network structure on the freeze-thaw stability of emulsion gels. The results showed that the addition of SA could form different types of network structures with SPI, due to different degrees of phase separation. In addition, SA appearing on the SPI network indicated that the addition of Ca2+ shielded the electrostatic repulsion between SPI and SA to form SPI-SA complexes. The disappearance of the characteristic peaks of SA and SPI in Fourier transform infrared spectroscopy analysis also confirmed this view. Low-field nuclear magnetic resonance data revealed that SA played a role in restricting water migration within the emulsion gels, increasing bound water content, and thereby improving the water-holding capacity of the emulsion gels. Therefore, the incorporation of SA improved the freeze-thaw stability of SPI emulsion gels. These findings offer a theoretical basis and technical support for SPI application in frozen products.

Lactoferrin-Chitosan Composite Hydrogels Induced by Microbial Transglutaminase: Potential Delivery Systems for Thermosensitive Bioactive Substances

In this work, lactoferrin (LF)-chitosan (CS) composite hydrogels with good loading capacity of thermosensitive bioactive substances were successfully obtained by microbial transglutaminase (MTG)-induced cross-linking. We evaluated the rheological, textural, and microstructural characteristics of the composite hydrogels under different conditions. The results demonstrated that the concentrations of LF and CS as well as the amount of MTG could regulate the textural properties, rheological properties, and water holding capability. The results of FTIR and fluorescence spectroscopy indicated that the main interactions within the composite gel were hydrogen and isopeptide bonds. Additionally, in vitro digestion simulation results verified that riboflavin kept stable in stomach due to the protection of LF-CS composite hydrogels and was released in small intestine. These results suggested that thermosensitive bioactive substance could be encapsulated and delivered by the LF-CS composite hydrogel, which could be applied in lots of potential applications in functional food as a new material.

The extraction of buckwheat protein and its interaction with kappa-carrageenan: Textural, rheological, microstructural, and chemical properties

Current plant-based foods use plant proteins as a key structuring and texturing ingredient. The use of water for extraction can replace conventional protein extraction methods. Water extraction of protein is environmentally friendly and could prevent the loss of protein functionality due to extreme pH changes. This study demonstrates an aqueous extraction method, coupled with ultrasound as pre-treatment, to obtain buckwheat protein (BWPE) and assess its gelling property and composited gel with kappa-carrageenan (k-carr). Textural and rheological analyses showed that the hardness and storage modulus of the composited gel containing 1 % w/w BWPE and 1 % w/w k-carr was 4.2-fold and 100-fold, respectively, higher than k-carr gel at 1 % w/w. Light microscopy showed a mixed bi-continuous gel system, with k-carr reinforcing the protein gel network. Besides volume exclusion effects, chemical bond and FTIR analyses revealed that adding k-carr to BWPE altered the protein's secondary structure and mediated protein denaturation during heating. This results in greater β-sheet content, which creates a more organised gel structure. These results demonstrated that ultrasound-assisted water-extracted BWPE, together with varying concentrations of k-carr, can be used to develop composited gels of tailorable textural and rheological properties to suit different food applications.

Formulations and assessments of structure, physical properties, and sensory attributes of soy yogurts: Effect of carboxymethyl cellulose content and degree of substitution

Soy yogurts present challenges, including absence of tender and slipperiness mouthfeel, and poor stability. This study aimed to investigate the impacts of carboxymethyl cellulose (CMC) with degrees of substitution of 0.7 (CMC0.7) and 1.2 (CMC1.2) at concentrations ranging from 0 % to 1.1 % on the stability, microstructure, rheology, tribology, and mouthfeel of soy yogurts. As the CMC concentration increased from 0 % to 0.3 %, soy yogurts displayed a coarser microstructure, decreased stability, and increased gel strength. As the concentration of CMC further increased from 0.5 % to 1.1 %, soy yogurts exhibited trends of a smoother microstructure, increased stability, and softer gel strength. Notably, soy yogurts with CMC0.7 demonstrated a superior water holding capacity (WHC) than soy yogurts with CMC1.2. Tribological measurements indicated that soy yogurts with CMC0.7 at a 0.7 % concentration had the lowest coefficient of friction (COF) value among most sliding speeds, showing a 23 % reduction compared to soy yogurts without CMC at a sliding speed of 10 mm/s. Moreover, sensory evaluation showed that soy yogurts with CMC0.7 at a 0.7 % concentration had the highest total score in mouthfeel evaluation. Therefore, the addition of CMC0.7 within the concentration range of 0.5 % to 1.1 % may produce stable and delicate yogurts.

Monovalent Salt and pH-Stimulated Gelation of Scallop (Patinopecten yessoensis) Male Gonad Hydrolysates/κ-Carrageenan

The gelation of scallop Patinopecten yessoensis male gonad hydrolysates (SMGHs) and κ-carrageenan (KC) subjected to pH (2-8, 3-9) and NaCl/KCl stimuli-response was investigated. SMGHs/KC gels subjected to a NaCl response exhibited an increasing storage modulus G'from 2028.6 to 3418.4 Pa as the pH decreased from pH 8 to 2, with corresponding T23 fluctuating from 966.40 to 365.64 ms. For the KCl-treated group, SMGHs/KC gels showed an even greater G' from 4646.7 to 10996.5 Pa, with T23 fluctuating from 622.2 to 276.98 ms as the pH decreased from 9 to 3. The improved gel strength could be ascribed to the blueshift and redshift of hydroxyl groups and amide I peaks, enhanced enthalpy and peak temperature, and gathered characteristic diffraction peaks from SMGHs, KC, NaCl, and KCl. The CLSM and cryo-SEM images further reflected that SMGHs/KC gels showed more flocculation formation and denser and more homogeneous networks with smaller pore sizes in more acidic domains, especially when subjected to the KCl response. This research gives a theoretical and methodological understanding of the construction of salt- and pH-responsive SMGHs/KC hydrogels as novel functional soft biomaterials applied in food and biological fields.

Legume protein/polysaccharide food hydrogels: Preparation methods, improvement strategies and applications

For the development of innovative foods and nutritional fortification, research into food gel is essential. As two types of rich natural gel material, both legume proteins and polysaccharides have high nutritional value and excellent application potential, attracting wide attention worldwide. Research has focused on combining legume proteins with polysaccharides to form hybrid hydrogels as their combinations show improved texture and water retention compared to single legume protein or single polysaccharide gels, and these properties can be tailored for specific applications. This article reviews hydrogels of common legume proteins and discusses heat induction, pH induction, salt ion induction, and enzyme-induced assembly of legume protein/polysaccharide mixtures. The applications of these hydrogels in fat replacement, satiety enhancement, and delivery of bioactive ingredients are discussed. Challenges for future work are also highlighted.

The preparation of soy glycinin/sugar beet pectin complex network gels catalyzed by laccase under weakly acidic conditions

BACKGROUND

Traditional soy protein gel products such as tofu, formed from calcium sulfate or magnesium chloride, have poor textural properties and water retention capacity. Soy glycinin (SG) is the main component affecting the gelation of soy protein and can be cross-linked with polysaccharides, such as sugar beet pectin (SBP), and can be modified by changing system factors (e.g., pH) to improve the gel's properties. Soy glycinin/sugar beet pectin (SG/SBP) complex double network gels were prepared under weakly acidic conditions using laccase cross-linking and heat treatment. The structural changes in SG and the properties of complex gels were investigated.

RESULTS

Soy glycinin exposed more hydrophobic groups and free sulfhydryl groups at pH 5.0. Under the action of laccase cross-linking, SBP could promote the unfolding of SG tertiary structures. The SG/SBP complex gels contained 46.77% β-fold content and had good gelling properties in terms of hardness 290.86 g, adhesiveness 26.87, and springiness 96.70 mm at pH 5.0. The T₂₂ relaxation time had the highest peak, and magnetic resonance imaging (MRI) showed that the gel had even water distribution. Scanning electron microscopy (SEM) and confocal scanning laser microscopy (CLSM) indicated that the SG/SBP complex network structure was uniform, and the pore walls were thicker and contained filamentous structures.

CONCLUSION

Soy glycinin/ sugar beet pectin complex network gels have good water-holding, rheological, and textural properties at pH 5.0. The properties of soy protein gels can be improved by binding to polysaccharides, with laccase cross-linked, and adjusting the pH of the solution. © 2022 Society of Chemical Industry.

Rational design cold-set interpenetrating network hydrogel based on wheat bran arabinoxylans and pea protein isolates for regulating the release of riboflavin in simulated digestion

Cold-set interpenetrating polymer network gels as riboflavin (RF) delivery vehicles based on wheat bran arabinoxylans (AX) and pea protein isolate (PPI) were developed via enzymatic-crosslinking. The impact of AX concentrations on the physicochemical property, in vitro digestion property and microstructure of IPN gels was explored. Increased concentrations of AX enhanced the viscoelasticity of IPN gels and resulted in a more compact microstructure. However, at a concentration of 5.0 % (w/v), the faster and stronger crosslinking of AX molecules caused separate network gel between PPI and AX. The IPN gel improved the encapsulation efficiency and release property of embedded RF as compared to PPI gel. SEM results showed that IPN gel maintained a complete network structure after gastric digestion. Particularly, the IPN gel with 1.0 % AX exhibited a homogeneous and complete network structure even after intestinal digestion, which explained the reason for the highest encapsulation efficiency and lowest release ratios of RF.

Physicochemical, Textural, and Sensorial Properties of Soy Yogurt as Affected by Addition of Low Acyl Gellan Gum

Soy yogurt is plant-based dairy of great nutritional interest that is widely accepted in developing countries as a milk alternative. Poor stability has been an urgent problem to solve of soy yogurt products over past several years. The present study aimed to construct multiple network composite gel by adding low acyl gellan gum (LAG) to improve the stability. The effect of addition of LAG on property of soy yogurt was investigated by determining water holding capacity, texture, rheology, particle size, and zeta potential. The results showed that water holding capacity was significantly higher than control. The soy yogurt with 0.1% LAG had a stable gel network with much gel strength and viscosity, and strengthened interaction between complex gel. The addition of LAG increased the particle size and decreased zeta potential. Furthermore, sensory properties were acceptable. Therefore, during industrial production, LAG could act as an appropriate stabilizer to inhibit poor body and bring more desirable sensory characteristics of soy yogurt.

Anionic exopolysaccharide from Cryptococcus laurentii 70766 as an alternative for alginate for biomedical hydrogels

Alginates are widely used polysaccharides for biomaterials engineering, which functional properties depend on guluronic and mannuronic acid as the building blocks. In this study, enzymatically crosslinked hydrogels based on sodium alginate (Na-Alg) and the exopolysaccharide (EPS) derived from Cryptococcus laurentii 70766 with glucuronic acid residues were synthesized and characterized as a new potential source of polysaccharide for biomaterials engineering. The EPS was extracted (1.05 ± 0.57 g/L) through ethanol precipitation. Then the EPS and Na-Alg were functionalized with tyramine hydrochloride to produce enzymatically crosslinked hydrogels in the presence of horseradish peroxidase (HRP) and H₂O₂. Major characteristics of the hydrogels such as gelling time, swelling ratio, rheology, cell viability, and biodegradability were studied. The swelling ratio and degradation profile of both hydrogels showed negative values, indicating an increased crosslinking degree and a lower water uptake percentage. The EPS hydrogel showed similar gelation kinetics compared to the Alg hydrogel. The EPS and its hydrogel were found cytocompatible. The results indicate the potential of EPS from C. laurentii 70766 for biomedical engineering due to its biocompatibility and degradability. Further studies are needed to confirm this EPS as an alternative for Alg in tissue engineering applications, particularly in the development of wound dressing products.

Ovarian Cell Encapsulation in an Enzymatically Crosslinked Silk-Based Hydrogel with Tunable Mechanical Properties

An artificial ovary is a promising approach for preserving fertility in prepubertal girls and women who cannot undergo current cryopreservation strategies. However, this approach is in its infancy, due to the possible challenges of creating a suitable 3D matrix for encapsulating ovarian follicles and stromal cells. To maintain the ovarian stromal cell viability and proliferation, as a first step towards developing an artificial ovary, in this study, a double network hydrogel with a high water swelling capacity (swelling index 15–19) was developed, based on phenol conjugated chitosan (Cs-Ph) and silk fibroin (SF) through an enzymatic crosslinking method using horseradish peroxidase. The addition of SF (1%) to Cs (1%) decreased the storage modulus (G’) from 3500 Pa (Cs1) to 1600 Pa (Cs-SF1), and the hydrogels with a rapid gelation kinetic produced a spatially homogeneous distribution of ovarian cells that demonstrated 167% proliferation after 7 days. This new Cs-SF hydrogel benefits from the toughness and flexibility of SF, and phenolic chemistry could provide the potential microstructure for encapsulating human ovarian stromal cells.

Albumin-based dynamic double cross-linked hydrogel with self-healing property for antimicrobial application

Hydrogels as ideal material are widely used in biomedical field against bacterial infection. Hydrogels synthesized from natural protein possess better biocompatibility than that synthesized from synthetic polymers. In this work, we designed bovine serum albumin (BSA) based hydrogel via double dynamic crosslinking. The cleavage and rearrangement of disulfide bonds of BSA triggered by glutathione (GSH) forms a disulfide bridge network, and tetrakis (hydroxymethyl) phosphonium sulfate (THPS) grafts the amino groups of BSA by a Mannich-type reaction to form a second network. Integrating THPS into the BSA/GSH system enables gel formation and endows excellent antimicrobial properties. Rheological tests showed the hydrogel featuring elasticity, good mechanical strength and self-healing properties. Antibacterial and cytotoxicity tests proved the hydrogel excellent bacteriostatic ability and low cytotoxicity. This albumin-based hydrogel with low cost is expected to realize wide biomedical applications.