Modeling creep/recovery behavior of cold-set gels using different approaches

Composite hydrogels fabricated from konjac glucomannan and gellan gum: Rheological characterization and their potential application in sustainable agriculture

In this study, konjac glucomannan (KG) was incorporated in high acyl gellan (HAG) and low acyl gellan (LAG) hydrogels in different ratios. The addition of KG increased pseudoplasticity and thermal hysteresis values of the hydrogels. Improvement in elasticity and water holding capacity (WHC) was observed in KG-LAG hydrogels. The highest WHC (98.5 %) was observed for 1K1H (KG:HAG = 1:1) and 3K7L (KG:LAG = 3:7) hydrogels. The crystallinity of the composite hydrogels was lower than hydrogels prepared from individual biopolymers. The hydrogels exhibited a rough surface with minute pores in the cross-section, due to the aggregation of glucomannan on the gellan network in the composite hydrogels. While HAG and 1K1H hydrogels exhibited greater swelling at low pH (3.0), LAG and 3K7L exhibited greater swelling at high pH (11.0). At pH 7.0, the hydrogels exhibited swelling indices >300 %. Incorporation of 1K1H hydrogel at 10 % (w/w) in sandy loamy soil under semi-arid conditions increased the germination of fenugreek microgreens from 60 % to 80 % on the 15th day. Furthermore, the moisture evaporation rate of the soil reduced from 35 % to <15 %, positively impacting the physicochemical properties of the microgreens. The composite hydrogels were successful in achieving a controlled release of phosphate fertilizer.

Improvement of physicochemical properties and quercetin delivery ability of fermentation-induced soy protein isolate emulsion gel processed by ultrasound

This study aimed to investigate the effects of ultrasonic treatment at different powers on the physicochemical properties, microstructure and quercetin delivery capacity of fermentation-induced soy protein isolate emulsion gel (FSEG). The FSEG was prepared by subjecting soy protein isolate (SPI) emulsion to ultrasonic treatment at various powers (0, 100, 200, 300, and 400 W), followed by lactic acid bacteria fermentation. Compared with the control group (0 W), the FSEG treated with ultrasound had higher hardness, water holding capacity (WHC) and rheological parameters. Particularly, at an ultrasonic power of 300 W, the FSEG had the highest hardness (101.69 ± 4.67 g) and WHC (75.20 ± 1.07%) (p < 0.05). Analysis of frequency sweep and strain scanning revealed that the storage modulus (G') and yield strains of FSEG increased after 300 W ultrasonic treatment. Additionally, the recovery rate after creep recovery test significantly increased from 18.70 ± 0.49% (0 W) to 58.05 ± 0.54% (300 W) (p < 0.05). Ultrasound treatment also resulted in an increased β-sheet content and the formation of a more compact micro-network structure. This led to a more uniform distribution of oil droplets and reduced mobility of water within the gel. Moreover, ultrasonic treatment significantly enhanced the encapsulation efficiency of quercetin in FSEG from 81.25 ± 0.62 % (0 W) to 90.04 ± 1.54% (300 W). The bioaccessibility of quercetin also increased significantly from 28.90 ± 0.40% (0 W) to 42.58 ± 1.60% (300 W) (p < 0.05). This study enriches the induction method of soy protein emulsion gels and provides some references for the preparation of fermented emulsion gels loaded with active substances.

Comparative analysis of soluble and insoluble dietary fiber on improving the gelation performance and fishy odors of silver carp surimi

This work investigated the effects and mechanisms of soluble and insoluble dietary fiber (SDF and IDF) on the gelation performance and fishy odors of silver carp surimi. The results showed that the gel properties of surimi increased and then decreased with increasing SDF content, and the best gel properties were achieved at 1 wt% SDF. The gel strength, elasticity and deformation resistance of surimi increased in a dose-dependent manner as affected by IDF, but its effect on viscosity and recovery ratio was similar to SDF. Moreover, 2 wt% SDF and 1 wt% IDF reduced the content and odor activity value (OAV) of most fishy compounds in surimi, and the latter was superior to the former. The rheological characteristics indicated that SDF affected the thermal gelation properties of surimi mainly through filling, concentration and volume exclusion, and IDF mainly through filling, concentration and intermolecular interactions between IDF and myofibrillar protein. Additionally, SDF and IDF inhibited the release of fishy odors by improving the gel network structure and their adsorption, but more SDF (2 wt%) promoted the formation of escape channels for odors release. In summary, 1 wt% IDF could simultaneously improve the gelation performance and fishy odors of silver carp surimi.

Stabilization of capsanthin in physically-connected hydrogels: Rheology property, self-recovering performance and syringe/screw-3D printing

This work presented a facile way of stabilizing capsanthin by physically-connected soft hydrogels via utilizing specially-structured polysaccharides, and investigated rheological properties, self-recovering mechanism and 3D printability. The functionalized hydrogels demonstrated excellent color quality including redness, yellowness index and hue with great storage stability and visual perception. The soft hydrogels fabricated with properly sequenced polyglyceryl fatty acid esters, β-cyclodextrin, chitosan, and low-content capsanthin possessed outstanding extrudability, appropriate yield stress, reasonable mechanical strength, rational elasticity and structure sustainability. Furthermore, the self-recovering properties based on hydrogen bonds, host-guest interactions and electrostatic interactions were revealed and verified by structural, zeta potential, micro-morphological, zeta potential, thixotropic, creep-recovery, and macroscopic/microscopic characterizations. Along with excellent antioxidant performance, the subsequent 3D printing onto bread with complex models elucidated the high geometry accuracy and great sensory characters. The sequenced physically-connected hydrogels incorporated with capsanthin can provide new insights on stabilizing hydrophobic biomaterials and developing the 3D printed exquisite, innovative food.

Impact of pH on pea protein-hydroxypropyl starch hydrogel based on interpenetrating network and its application in 3D-printing

Improving the mechanical and 3D printing performance of pea protein (PeaP) hydrogels contributes to the development of innovative plant-based gel products. Herein, we proposed a strategy for constructing PeaP-hydroxypropyl starch (HPS) interpenetrating network hydrogels, in which the structure, strength, and 3D printing properties of the hydrogels were regulated by changing pH. Results showed that pH significantly affected the gelation process of PeaP/HPS hydrogels. The hydrogels formed a lamellar structure at pH 3, a granule aggregation network structure at pH 5, porous structures at pH 7 and 9, and a honeycomb structure at pH 11. The strength of hydrogels formed at different pH values had the following order: pH 3 ＞pH 11 ＞ pH 7 ＞pH 9 ＞pH 5. The storage modulus (G') of the hydrogel at pH 3 was up to 4149 Pa, but only 695 Pa at pH 5. Moreover, hydrogel at pH 3 had the best self-recovery of 55%. 3D printed objects from gel inks at pH 3 exhibited high structural integrity and fidelity at 60 °C. Gelling force analysis indicated hydrogen bonds were the dominant interaction within all hydrogels. Overall, this study suggested that PeaP/HPS hydrogel formed at pH 3 possessed the most excellent mechanical properties and 3D printing capabilities, which may provide insights into the development of novel PeaP-based gel food ingredients and promote the application of PeaP in the food industry.

Rheology as a Tool for Fine-Tuning the Properties of Printable Bioinspired Gels

Over the last decade, efforts have been oriented toward the development of suitable gels for 3D printing, with controlled morphology and shear-thinning behavior in well-defined conditions. As a multidisciplinary approach to the fabrication of complex biomaterials, 3D bioprinting combines cells and biocompatible materials, which are subsequently printed in specific shapes to generate 3D structures for regenerative medicine or tissue engineering. A major interest is devoted to the printing of biomimetic materials with structural fidelity after their fabrication. Among some requirements imposed for bioinks, such as biocompatibility, nontoxicity, and the possibility to be sterilized, the nondamaging processability represents a critical issue for the stability and functioning of the 3D constructs. The major challenges in the field of printable gels are to mimic at different length scales the structures existing in nature and to reproduce the functions of the biological systems. Thus, a careful investigation of the rheological characteristics allows a fine-tuning of the material properties that are manufactured for targeted applications. The fluid-like or solid-like behavior of materials in conditions similar to those encountered in additive manufacturing can be monitored through the viscoelastic parameters determined in different shear conditions. The network strength, shear-thinning, yield point, and thixotropy govern bioprintability. An assessment of these rheological features provides significant insights for the design and characterization of printable gels. This review focuses on the rheological properties of printable bioinspired gels as a survey of cutting-edge research toward developing printed materials for additive manufacturing.