4D printing of lotus root powder gel: Color change induced by microwave

Recent advances on enhancing 3D printing quality of protein-based inks: A review

3D printing is an additive manufacturing technology that locates constructed models with computer-controlled printing equipment. To achieve high-quality printing, the requirements on rheological properties of raw materials are extremely restrictive. Given the special structure and high modifiability under external physicochemical factors, the rheological properties of proteins can be easily adjusted to suitable properties for 3D printing. Although protein has great potential as a printing material, there are many challenges in the actual printing process. This review summarizes the technical considerations for protein-based ink 3D printing. The physicochemical factors used to enhance the printing adaptability of protein inks are discussed. The post-processing methods for improving the quality of 3D structures are described, and the application and problems of fourth dimension (4D) printing are illustrated. The prospects of 3D printing in protein manufacturing are presented to support its application in food and cultured meat. The native structure and physicochemical factors of proteins are closely related to their rheological properties, which directly link with their adaptability for 3D printing. Printing parameters include extrusion pressure, printing speed, printing temperature, nozzle diameter, filling mode, and density, which significantly affect the precision and stability of the 3D structure. Post-processing can improve the stability and quality of 3D structures. 4D design can enrich the sensory quality of the structure. 3D-printed protein products can meet consumer needs for nutritional or cultured meat alternatives.

Recent Advances in 4D Printing of Advanced Materials and Structures for Functional Applications

4D printing has attracted tremendous worldwide attention during the past decade. This technology enables the shape, property, or functionality of printed structures to change with time in response to diverse external stimuli, making the original static structures alive. The revolutionary 4D-printing technology offers remarkable benefits in controlling geometric and functional reconfiguration, thereby showcasing immense potential across diverse fields, including biomedical engineering, electronics, robotics, and photonics. Here, a comprehensive review of the latest achievements in 4D printing using various types of materials and different additive manufacturing techniques is presented. The state-of-the-art strategies implemented in harnessing various 4D-printed structures are highlighted, which involve materials design, stimuli, functionalities, and applications. The machine learning approach explored for 4D printing is also discussed. Finally, the perspectives on the current challenges and future trends toward further development in 4D printing are summarized.

The color/shape/flavor of yam gel with double emulsified microcapsules changed synchronously in 4D printing induced by microwave

The feasibility of 3D printing the color, aroma and shape changes of yam gel with microwave heating as stimulus and soybean protein isolate-chitosan-maltodextrin complex coacervated microcapsules rich in water-soluble betacyanin and rose essence as stimulus-response materials was discussed. The morphology of microcapsules presented irregular spherical structure, and the surface was relatively smooth and slightly concave. Microwave heating led to the gradual destruction of microcapsules in yam gel, releasing internal pigments and essence, and enhancing the redness and flavor of printed samples. The release of the water phase and oil phase of the microcapsules and the hot-spot expansion effect of the models made the 3D printed bird models bend and deform, realizing the deformation effect of "spreading of wings", which realized a three-response synchronous change in color, shape, and flavor of the printed samples within 45 s. In this study, a variety of 4D printed foods with synchronous changes in sensory characteristics were created, which increased sensory enjoyment on the basis of ensuring the nutritional needs of food.

Investigation of 3D printing product of powder-based white mushroom incorporated with soybean protein isolate as dysphagia diet

The elderly people are prone to dysphagia due to weakened muscle strength. 3D food printing could modify the nutritional ratio and shape design to produce personalized nutritious food suitable for patients with dysphagia. White mushroom (Agaricus bisporus) is rich in a variety of active ingredients such as polysaccharides and polyphenols which are beneficial to human body, but its unique texture is not suitable for patients with dysphagia to chew. This study investigated the impact of different concentrations of soybean protein isolate (SPI, 3%, 5%, 7%, w/w) on 3D food printing of white mushroom powder and carried out the hierarchical representation of dysphagia diet within the framework of International Dysphagia Diet Standardization Initiative (IDDSI). The results illustrated that SPI addition to white mushroom gel reduced water mobility and promoted hydrogen bond formation, which significantly improved the mechanical strength and cohesiveness of printing inks, including yield stress, viscosity and hardness. IDDSI tests showed that the SPI addition of 3% and 5% helped the printing ink pass the spoon tilt test and the fork drip test, which could be classified as level 5 minced and moist food under the consideration of the fork pressure test. The 3D printing results indicated that the 7% SPI addition made the yield stress too high and was not easy for extrusion, resulting in the appearance defects of the printed sample. The addition of 3% SPI could make the printed sample have smooth surface and excellent self-supporting capacity. This work provides insights of white mushroom 3D printing technology as a more visually appealing dysphagia diet.

Microwave-induced rapid 4D change in color of 3D printed apple/potato starch gel with red cabbage juice-loaded WPI/GA mixture

This study aimed to explore the feasibility of utilizing microparticle mixture (MCPs) comprised of whey protein isolate (WPI), gum Arabic (GA), and freeze-dried red cabbage juice (FDRCJ) as a smart material to realize a rapid color change of 3D printed apple/potato starch gel in response to microwave heating stimulation. The particle size, morphology and thermal stability of WPI/FDRCJ/GA microparticles were examined. Then, the rheology, texture properties and printability of Apple/potato starch gel affected by different concentrations of WPI/FDRCJ/GA microparticles (0, 15, 30, 45, 60% (w/w)) were studied. Results showed that the WPI/FDRCJ/GA microparticles were more thermally stable than pure materials, indicating that the heat-sensitive anthocyanin and other compounds present in FDRCJ were effectively protected by the wall materials (WPI/GA). Moreover, the addition of various microparticle concentrations decreased the samples' mechanical properties but had no significant influence on their loss modulus, viscosity, or printing accuracy. As the microwave heating time increased, the lightness (L*) and yellowness (b*) of microparticle-added samples decreased while the redness (a*) significantly increased (p < 0.05), resulting in a gradual color change from yellow/brown to red. These findings could be useful to produce novel colorful and appealing 4D healthy food products that stimulate consumer appetite.

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.

Rheological property, β-carotene stability and 3D printing characteristic of whey protein isolate emulsion gels by adding different polysaccharides

Emulsion gels with unique structural and mechanical properties have promising applications in 3D food printing. The purpose of this paper was to investigate the rheological property, β-carotene stability and 3D printing characteristic of whey protein isolate (WPI) emulsion gels by adding guar gum (GG), locust bean gum (LBG), xanthan gum (XG) and gum arabic (GA). The results showed that all samples exhibited shear thinning behavior and elastic characteristic. XG could reduce water mobility and increase WHC of WPI emulsion gel. The disulfide bond was the main chemical molecular force of emulsion gels, and XG significantly increased the hydrophobic interactions. GG and LBG increased gel strength, hardness and gumminess, reduced springiness, cohesiveness and chewiness of emulsion gels. GG sample had the best printing performance, more uniform network structure and better stability of β-carotene. This study provided a theoretical basis for 3D printing functional food.

Microwave-Induced Rapid Shape Change of 4D Printed Vegetable-Based Food

Microwave heating acts as an environmental stimulus factor to induce rapid shape changes in 4D-printed stereoscopic models over time. The influence of microwave power and model structure on the shape change behavior was explored, and the applicability of the deformed method to other vegetable-based gels was verified. The results described that the G', G″, η, and proportion of bound water of yam gels increased with the increase in yam powder content, and the yam gel with 40% content had the best printing effect. The IR thermal maps showed the microwaves first gathered in the designed gully region caused the swelling phenomenon, which induced the printed sample to undergo a bird-inspired "spreading of wings" process within 30 s. Increasing the microwave power and microwave heating time were able to increase the bending angles and dehydration rates of the printed samples, thus improving the deformed degree and deformed speed. Different model base thicknesses (4, 6, 8, and 10 mm) also had significant effects on the shape change of the printed structures. The efficiency of the shape changes of 4D-printed structures under microwave induction can be judged by studying the dielectric properties of the materials. In addition, the deformed behaviors of other vegetable gels (pumpkin and spinach) verified the applicability of the 4D deformed method. This study aimed to create 4D-printed food with personalized and rapid shape change behavior, providing a basis for the application scenarios of 4D-printed food.

Microwave-Triggered 4D Automatic Color Change in 3D-Printed Food Materials Incorporating Natural Pigments

The feasibility of using microwaves to quickly stimulate automatic color change in 3D-printed food containing curcumin or anthocyanins was studied. Firstly, with a dual-nozzle 3D printer, stacked structures included mashed potatoes (MPs, upper part, containing anthocyanins) and lemon juice-starch gel (LJSG, lower part) were 3D-printed and post-treated using a microwave. The results indicated that the viscosity and gel strength (indicated by the elastic modulus (G') and complex modulus (G*)) of LJSG were improved with the increase in starch concentration, while water mobility was reduced. During microwave post-treatment, the color change speed was negatively correlated with the gel strength but positively correlated with the diffusion of H⁺ and anthocyanin concentration. Secondly, nested structures were 3D-printed using MPs containing curcumin emulsion and baking soda (NaHCO₃). During microwave post-treatment, the curcumin emulsion structure was destroyed, and NaHCO₃ was decomposed, along with an increase in alkalinity; thus, the automatic color change was achieved with the automated presentation of hidden information. This study suggests that 4D printing could enable the creation of colorful and attractive food structures using a household microwave oven, leading to more imaginative solutions regarding personalized foods, which may be particularly important to people with poor appetites.

Advances in the Potential Application of 3D Food Printing to Enhance Elderly Nutritional Dietary Intake

The contradiction between the growing demand from consumers for "nutrition & personalized" food and traditional industrialized food production has consistently been a problem in the elderly diet that researchers face and discuss. Three-dimensional (3D) food printing could potentially offer a solution to this problem. This article reviews the recent research on 3D food printing, mainly including the use of different sources of protein to improve the performance of food ink printing, high internal phase emulsion or oleogels as a fat replacement and nutrition delivery system, and functional active ingredients and the nutrition delivery system. In our opinion, 3D food printing is crucial for improving the appetite and dietary intake of the elderly. The critical obstacles of 3D-printed food for the elderly regarding energy supplements, nutrition balance, and even the customization of the recipe in a meal are discussed in this paper. By combining big data and artificial intelligence technology with 3D food printing, comprehensive, personalized, and customized geriatric foods, according to the individual traits of each elderly consumer, will be realized via food raw materials-appearance-processing methods. This article provides a theoretical basis and development direction for future 3D food printing for the elderly.

Sustainable and Bio-Based Food Packaging: A Review on Past and Current Design Innovations

Food loss and waste occur for many reasons, from crop processing to household leftovers. Even though some waste generation is unavoidable, a considerable amount is due to supply chain inefficiencies and damage during transport and handling. Packaging design and materials innovations represent real opportunities to reduce food waste within the supply chain. Besides, changes in people's lifestyles have increased the demand for high-quality, fresh, minimally processed, and ready-to-eat food products with extended shelf-life, that need to meet strict and constantly renewed food safety regulations. In this regard, accurate monitoring of food quality and spoilage is necessary to diminish both health hazards and food waste. Thus, this work provides an overview of the most recent advances in the investigation and development of food packaging materials and design with the aim to improve food chain sustainability. Enhanced barrier and surface properties as well as active materials for food conservation are reviewed. Likewise, the function, importance, current availability, and future trends of intelligent and smart packaging systems are presented, especially considering biobased sensor development by 3D printing technology. In addition, driving factors affecting fully biobased packaging design and materials development and production are discussed, considering byproducts and waste minimization and revalorization, recyclability, biodegradability, and other possible ends-of-life and their impact on product/package system sustainability.

Construction of 3D printed meat analogs from plant-based proteins: improving the printing performance of soy protein- and gluten-based pastes facilitated by rice protein

Additive technology (3D printing) is increasingly being used to produce plant-based meat analogs. However, there are several challenges to fabricating meat analogs using this technology: (i) the protein content in the final printed product is often too low to match the nutritional profile of real meat; (ii) it is often difficult to accurately mimic the textural and structural attributes of real meat using existing plant protein edible inks. In this study, the rheological properties and printing performance of edible inks produced from soy protein isolate (SPI), wheat gluten (WG), and rice protein (RP) were investigated. Our goal was to mix SPI, WG, RP powders to develop a high-protein edible ink (25% of total dry matter content) that can be used to create 3D-printed meat analogs. The rheological properties, moisture distribution, texture, microstructure, and printing performance (fidelity and stability) of protein pastes with different SPI-WG-to-RP ratios were measured. These protein-enriched inks exhibited pseudoplastic behavior with viscoelastic properties. The apparent viscosity and storage modulus of these pastes decreased with increasing rice protein proportion, which improved their 3D printing performance, such as hardness, support force, and plasticization. These edible inks prepared by mixed protein may be useful for 3D printing of plant-based foods.

Impact of internal structural design on quality and nutritional properties of 3D printed food products during post-printing: a critical review

3D food printing (3DFP) provides an excellent opportunity to deposit layers of multiple food materials to create unique complex structures of products with more engaging visuals, specific textures, and customized nutritional properties. Many printed products require post-printing processing which can result in sensory variance, texture changes, and even nutritional modification. Hence it is necessary to implement the design of the complex internal structure to ensure the desired quality of the printed products following post-printing. 3-D printing of various types of food products, for example, chocolate, cheese, meat, vegetables, fruits, fish, eggs, cereal-based products, and so on, has been examined with regard to post-printing requirements. This review aims to summarize the current work on the latest developments in 3DFP technology concerning the internal structure design of 3D printed products and its effect on quality during post-printing. The quality parameters include: textural, physical, morphological, and dimensional characteristics as well as nutritional properties. Furthermore, post-printing modifications such as 4D are also analyzed.

Defects in 3D/4D food printing and their possible solutions: A comprehensive review

3D food printing has recently attracted significant attention, both from academic and industrial researchers, due to its ability to manufacture customized products in such terms as size, shape, texture, color, and nutrition to meet demands of individual consumers. 4D printing, which is a technique that allows evolution of various characteristics/properties of 3D printed objects over time through external stimulation, has also been gaining more attention. In order to produce defect-free printed objects via both 3D and 4D printing, it is necessary to first identify the causes of defects and then their mitigation strategies. Comprehensive review on these important issues is nevertheless missing. The purpose of this review is to investigate causes and characteristics of defects occurring during and/or after 3D food printing, with a focus on how different factors affect the printing accuracy. Various techniques that can potentially minimize or eliminate printing defects and produce high-quality 3D/4D printed food products without the need for time-consuming trial and error printing experiments are critically discussed. Guidelines to avoid defects to improve the efficiency of future 3D/4D printed food production are given.

Research progress in fluid and semifluid microwave heating technology in food processing

Microwave is a form of electromagnetic radiation that has high penetration and heating efficiency in food processing. Uneven heating is the main problem of microwave processing, especially in solid foods. Fluid and semifluid media, which are good carriers in microwave processing, have uniform dielectric properties and good material fluidity. Herein, we review the development, application prospects, and limitations of microwave in fluid and semifluid food processing and the research progress in microwave heating with steam as carrier. The mixture of generated steam and tiny micro droplets from food material under the action of microwave can absorb microwave and transfer heat evenly, which effectively improves the uniformity of microwave heating. Due to the relatively uniform dielectric properties and consistent texture of fluid and semifluid food materials, uneven heating phenomenon during their microwave processing can be significantly inhibited. Based on the development of microwave heating technology and equipment design, the microbial inactivation and enzyme inhibition in fluid and semifluid food were improved and food product with better retention of nutrients and sensory profile were produced. Also, microwave radiation can be used to prepare the printing material or process the printed product for 3D food printing, which enhances the added value of 3D printed products and the personalization of food manufacturing. In future research, intelligent control technology can be applied in the microwave processing of fluid and semifluid food materials for various applications. Therefore, the processing conditions can be adjusted automatically.

Effect of beef tallow, phospholipid and microwave combined ultrasonic pretreatment on Maillard reaction of bovine bone enzymatic hydrolysate

The effects of beef tallow, phospholipid, microwave, and ultrasonic pretreatment (MUP) on the Maillard reaction process, the sensory characteristics of Maillard reaction products (MRPs), and the composition and content of volatile compounds were studied. Maillard reaction of the sample was more intense after MUP, but more hydrophobic amino acids were generated, resulting in relatively high sourness in MRPs. Beef tallow encapsulation has no significant effect on the sensory characteristics of MRPs. The content of volatile compounds in MRPs added with phospholipids increased significantly, and the content of sulfur compounds (especially furan and furanthiol) increased most significantly. Hexanal, Nonanal, 2-Hexylfuran, 2-Hexylthiophene, and 1-Octanol were positively correlated with the value of umami and saltiness of MRPs. The addition of phospholipids after MUP and beef tallow encapsulation helps to increase the saltiness and umami of MRPs, reduce astringency, and produce more sulfur and other flavor compounds.

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.

Advances and prospective applications of 3D food printing for health improvement and personalized nutrition

Three-dimensional food printing (3DFP) uses additive manufacturing concepts to fabricate customized designed products with food ingredients in powder, liquid, dough, or paste presentations. In some cases, it uses additives, such as hydrocolloids, starch, enzymes, and antibrowning agents. Chocolate, cheese, sugar, and starch-based materials are among the most used ingredients for 3DFP, and there is a broad and growing interest in meat-, fruit-, vegetable-, insect-, and seaweed-based alternative raw materials. Here, we reviewed the most recent published information related to 3DFP for novel uses, including personalized nutrition and health-oriented applications, such as the use of 3D-printed food as a drug vehicle, and four-dimensional food printing (4DFP). We also reviewed the use of this technology in aesthetic food improvement, which is the most popular use of 3DFP recently. Finally, we provided a prospective and perspective view of this technology. We also reflected on its multidisciplinary character and identified aspects in which social and regulatory affairs must be addressed to fulfill the promises of 3DFP in human health improvement.

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

The feasibility was investigated of 4D printing of lotus root gel compounded with a pigment that responds to pH change and alters colour. The pigment comprised of a combination of anthocyanins and lemon yellow; it was used in gel preparation for printing. The flowability and self-support properties of the lotus root-pigment gel were studied to evaluate its 3D printing performance. The gel viscosity decreased with the increase of printing temperature over the range 40, 50, and 60 °C. The gel with a ratio (lotus root powder/compound pigment) of 0.35 extruded smoothly and maintained high formability at temperatures below 60 °C. The pH response of compound pigment enabled the printed sample to change colour from reddish/yellowish to green after spraying with NaHCO₃. The a* and b* values decreased significantly (p < 0.05) after spraying for 1 min. The gel with ratios of 0.30 and 0.35 achieved rapid colour change both superficially and internally. Through several different model designs (apple, Christmas tree, letters, and Chinese characters), high-quality 4D printing could be realized without problem. Thus, lotus root gel can be mixed with suitable pigments in correct proportion for 4D printing at appropriate temperature to ensure good flowability.

New insights into food O/W emulsion gels: Strategies of reinforcing mechanical properties and outlook of being applied to food 3D printing

3D printing technology has been widely used in food processing with its advantages of customized food design, personalized nutrition design, and simplified food supply chain. Food emulsion gels have application value and prospects in food 3D printing due to their promising properties, including biodegradability, biocompatibility, as well as dual characteristics of emulsions and biopolymer gels. Food emulsion gels with appropriate mechanical properties, as a new type of food inks, expand the types and functions of the inks. However, food emulsion gels without adequate reinforced mechanical properties may suffer from defects in shape, texture, mouthfeel, and functionality during 3D printing and subsequent applications. Therefore, it is necessary to summarize the strategies to improve the mechanical properties of food emulsion gels. According to the methods of characterizing the mechanical properties of emulsion gels, this article summarizes four strategies for improving the mechanical properties of emulsion gels through two ways: inside-out (reinforcement of interface and reinforcement of cross-linking) and outside-in (physical approaches and environmental regulations), as well as their basic mechanisms. The application status and future research trends of emulsion gels in food 3D printing are finally discussed.

3D and 4D printing: From innovation to evolution

The world and science are moving forward nonstop. Every day, we see novel technologies that are coming to improve life quality. One of them is 3D printing or additive manufacturing. This technology covers the shortage of the current manufacturing technologies, and it has been enhanced by introducing smart materials like smart polymers as feed. The following product can adapt to circumstance conditions such as temperature changes, compression alteration, etc. These responses resulted in an advanced 3D printing technology called 4D printing. 3D and 4D printing technologies found their applications in all areas and industry sizes, from home-scale to large-scale industries. Regardless of all advantages of these technologies, there are still some shortages like low printing speed. But this never stops their progression and promotion. In this review, we aimed to cover general knowledge about 3D and 4D printing and their recent applications in various fields.