Investigation of 4D printing of lotus root-compound pigment gel: Effect of pH on rapid colour change

Sodium tripolyphosphate crosslinking enhancement on shikonin-loaded gelatin emulsions with high structure stability and its application in 4D printing

Shikonin was loaded into gelatin complex nanoparticles induced by sodium tripolyphosphate crosslinking enhancement, which could stabilize high internal phase emulsions for possible four-dimensional printing. Complex nanoparticles (446 nm) based emulsions possess excellent red colors and centrifugation stability. Rheology results indicate that sodium tripolyphosphate can promote the emulsions to own the outstanding thixotropy properties (high thixotropic hysteresis loop area 6646 Pa s-1, and high recovery rate), shear-thinning behavior (power law index<1), yield stress (around 169 Pa), viscoelastic performance (high elastic modulus with high mechanic strength), and thermal resistance. Optical microscopy suggests the low-size, stable droplets with good freezing-thawing and heating endurance in emulsions. Finally, gelatin-shikonin complex nanoparticles based emulsions presents the excellent four-dimensional printability with great dynamic response to pH. This study provides important implications for producing stable emulsions for four-dimensional printing of novel, colorful, functional food products.

3D printing performance of whole lotus root powder and lotus root starch

The evaluation of rheological properties and printability of whole-component foods is crucial for 3D printing. However, the properties of nutrient-rich whole lotus root powder (WL) remain poorly understood. Key experimental results demonstrated that WL at concentrations ranging from 10 % to 25 % exhibited superior printability compared to lotus root starch (LS). Specifically, WL achieved a lower shape deviation (sd = 9.76 % vs. 30.10 % for LS at 15 % concentration) and maintained a stable filament diameter (1.25 ± 0.021 mm) closer to the nozzle size (1.2 mm). The high viscosity of lotus root starch gel (LSG) hindered its extrusion from the printer nozzle, causing improper sample formation. In contrast, WL gels (WLG) showed enhanced water retention and reduced hardness, attributed to interactions among components such as fiber and lipids. These properties allowed WL-printed samples (WLP) to retain a soft and elastic texture even after prolonged storage. Thermogravimetric analysis further confirmed the improved thermal stability of WL, with a 20 % lower mass loss at 280-400 °C compared to LS. Overall, WL proved more suitable for 3D printing, providing a theoretical basis for integrating lotus root into printed foods and advancing practical applications in nutritional food production.

Stabilization of oil-in-water high internal phase Pickering emulsion by using 7S globulin/konjac glucomannan complexes: Rheology properties, stability properties and 3D/4D printing performance

Food-grade compound-stabilized high internal phase Pickering emulsions (HIPPEs) have attracted considerable interest in the food industry and the field of functional foods. Nonetheless, challenges persist regarding the integration of active ingredients and the need for swift processing and shaping in food manufacturing. In this study, the effects of different konjac glucomannan (KGM) concentrations (0 %, 0.125 %, 0.25 %, 0.375 %, 0.50 %, 0.625 % w/v) on the gel network structure, rheology properties (shear-thinning behavior, viscoelasticity, and thixotropic recovery), stability properties and 3D/4D printing properties of HIPPEs stabilized with 7S globulin (7S) were investigated. KGM (≤0.375 %) facilitated the formation of gel network structure, thus hindering oil droplet aggregation. Moreover, the HIPPEs stabilized by 7S-KGM could be used as food-grade inks for 3D printing, thanks to their excellent solid-like viscoelasticity, moderate shear thinning behavior, and outstanding thixotropic recovery. The HIPPEs prepared with the 7S-KGM0.375 complexes exhibited the best performance, and the resulting 3D printed models demonstrated good precision and stability. Furthermore, the prepared HIPPEs demonstrated excellent heating stability and lipid oxidation stability. The results of 4D printing showed that the appropriate concentration of KGM could significantly enhance the density of gel network structure of printed samples, thus inhibiting the transfer of curcumin from the oil phase into the aqueous phase, which resulted in an inconspicuous change in the color of the sample. However, the KGM (>0.375 %) produced the opposite effect. These findings fully leveraged the advantages of personalized customization in 3D printing technology, enriching the application scenarios of HIPPEs in 3D printing.

Digital light processing printing of non-modified protein-only compositions

This study explores the utilization of digital light processing (DLP) printing to fabricate complex structures using native gelatin as the sole structural component for applications in biological implants. Unlike approaches relying on synthetic materials or chemically modified biopolymers, this research harnesses the inherent properties of gelatin to create biocompatible structures. The printing process is based on a crosslinking mechanism using a di-tyrosine formation initiated by visible light irradiation. Formulations containing gelatin were found to be printable at the maximum documented concentration of 30 wt%, thus allowing the fabrication of overhanging objects and open embedded. Cell adhesion and growth onto and within the gelatin-based 3D constructs were evaluated by examining two implant fabrication techniques: (1) cell seeding onto the printed scaffold and (2) printing compositions that contain cells (cell-laden). The preliminary biological experiments indicate that both the cell-seeding and cell-laden strategies enable making 3D cultures of chondrocytes within the gelatin constructs. The mechanical properties of the gelatin scaffolds have a compressive modulus akin to soft tissues, thus enabling the growth and proliferation of cells, and later degrade as the cells differentiate and form a grown cartilage. This study underscores the potential of utilizing non-modified protein-only bioinks in DLP printing to produce intricate 3D objects with high fidelity, paving the way for advancements in regenerative tissue engineering.

Development of 3D printed k-carrageenan-based gummy candies modified by fenugreek gum: Correlating 3D printing performance with sol-gel transition

Temperature-responsive inks were formulated using k-carrageenan, fenugreek gum (FG), rose extracts, and sugar, of which the first two were used as the gelling agents. The interactions among components in these mixed ink formulations were investigated. Sol-gel transition and rheological properties of these inks were also correlated with extrusion, shape formation, and self (shape)-supporting aspects of 3D printing. Results indicated that incorporating FG increased inks' gelation temperature from 39.7 °C to 44.7-49.6 °C, affecting the selection of printing temperature (e.g., 0 % FG: 40 °C, 0.15 % FG: 45 °C, 0.3 % FG-0.6 % FG: 50 °C). Inks in solution states with lower viscosity (<5 Pa·s) were amenable to ensure their smooth extrusion through the tip of the printing nozzle. A shorter sol-gel transition time (approximately 100 s) during the shape formation stage facilitated the solidification of inks after extrusion. The addition of FG significantly (p<0.05) improved the mechanical properties (elastic modulus, hardness, etc.) of the printed models, which facilitated their self-supporting behavior. Low field nuclear magnetic resonance indicated that the inclusion of FG progressively restricted water mobility, consequently reducing the water syneresis rate of the mixed inks by 0.86 %-3.6 %. FG enhanced hydrogen bonding interactions among the components of these mixed inks, and helped to form a denser network.

Four-Dimensional (4D) Printing of Dynamic Foods-Definitions, Considerations, and Current Scientific Status

Since its conception, the application of 3D printing in the structuring of food materials has been focused on the processing of novel material formulations and customized textures for innovative food applications, such as personalized nutrition and full sensory design. The continuous evolution of the used methods, approaches, and materials has created a solid foundation for technology to process dynamic food structures. Four-dimensional food printing is an extension of 3D printing where food structures are designed and printed to perform time-dependent changes activated by internal or external stimuli. In 4D food printing, structures are engineered through material tailoring and custom designs to achieve a transformation from one configuration to another. Different engineered 4D behaviors include stimulated color change, shape morphing, and biological growth. As 4D food printing is considered an emerging application, imperatively, this article proposes new considerations and definitions in 4D food printing. Moreover, this article presents an overview of 4D food printing within the current scientific progress, status, and approaches.

Effects of magnetic field-assisted liquid carbon dioxide spray freezing on the quality of honeydew melon

The effectiveness of static magnetic fields with different intensities (5, 10, 15 mT) combined with liquid carbon dioxide spray freezing (LCSF) technique in improving the quality of frozen honeydew melon was investigated. The results showed that LCSF with magnetic fields above 10 mT significantly improved ice nucleation and quality of frozen melons compared to conventional -20 °C freezing, -80 °C freezing and LCSF method without magnetic field assistance (P < 0.05). 15 mT strength static magnetic field assistance suggested the best results, with a 15.0% reduction in total freezing time, 17.7% increase in average freezing rate, 26.6% reduction in drip loss, and better maintenance of sample quality compared to LCSF. These findings demonstrate that LCSF with static magnetic field assistance is promising in improving the quality of frozen foods.

Bioprinting for bone tissue engineering

The shape transformation characteristics of four-dimensional (4D)-printed bone structures can meet the individual bone regeneration needs, while their structure can be programmed to cross-link or reassemble by stimulating responsive materials. At the same time, it can be used to design vascularized bone structures that help establish a bionic microenvironment, thus influencing cellular behavior and enhancing stem cell differentiation in the postprinting phase. These developments significantly improve conventional three-dimensional (3D)-printed bone structures with enhanced functional adaptability, providing theoretical support to fabricate bone structures to adapt to defective areas dynamically. The printing inks used are stimulus-responsive materials that enable spatiotemporal distribution, maintenance of bioactivity and cellular release for bone, vascular and neural tissue regeneration. This paper discusses the limitations of current bone defect therapies, 4D printing materials used to stimulate bone tissue engineering (e.g., hydrogels), the printing process, the printing classification and their value for clinical applications. We focus on summarizing the technical challenges faced to provide novel therapeutic implications for bone defect repair.

Progress in 4D/5D/6D printing of foods: applications and R&D opportunities

4D printing is a result of 3D printing of smart materials which respond to diverse stimuli to produce novel products. 4D printing has been applied successfully to many fields, e.g., engineering, medical devices, computer components, food processing, etc. The last two years have seen a significant increase in studies on 4D as well as 5D and 6D food printing. This paper reviews and summarizes current applications, benefits, limitations, and challenges of 4D food printing. In addition, the principles, current, and potential applications of the latest additive manufacturing technologies (5D and 6D printing) are reviewed and discussed. Presently, 4D food printing applications have mainly focused on achieving desirable color, shape, flavor, and nutritional properties of 3D printed materials. Moreover, it is noted that 5D and 6D printing can in principle print very complex structures with improved strength and less material than do 3D and 4D printing. In future, these new technologies are expected to result in significant innovations in all fields, including the production of high quality food products which cannot be produced with current processing technologies. The objective of this review is to identify industrial potential of 4D printing and for further innovation utilizing 5D and 6D printing.