Investigation on spontaneous 4D changes in color and flavor of healthy 3D printed food materials over time in response to external or internal pH stimulus

Four-dimensional food printing: A revolutionary approach to next-generation foods

Four-dimensional (4D) food printing is a cutting-edge technology that allows the creation of shape-shifting transformative food structures. This innovative approach to food design enables food scientists to craft edible creations that change form and texture over time, thereby providing a unique and dynamic dining experience. Beyond its novelty and aesthetic appeal, 4D food printing has practical applications that address pressing issues in the food industry. In this review, we explore the technology behind 4D food printing, food ink types, and other natural ingredients that can be programed to change shape with stimuli, and the possibilities and potential applications of 4D food printing, from tantalizing taste sensations to revolutionary solutions for food sustainability, and explore the latest research and innovations in this field. Ultimately, 4D food printing represents a new frontier in food processing and culinary arts, offering fresh canvas for creative expression, a means to address pressing food-related challenges, and a way to rethink our relationship with the food we eat.

Effect of galactomannan addition on the rheological property, 3D printing performance and flavor characteristic of shepherd's purse gels

Shepherd's purse is a herbaceous plant that has been widely used in China because it contains many kinds of nutrients. The application of shepherd's purse in 3D printing food can realize the personalized customization of a healthy diet. This study aims to evaluate the effects of galactomannan types, including locust bean gum (LBG), tara gum (TG), guar gum (GG), and fenugreek gum (FG), on the rheological properties, 3D printing performance and flavor characteristics of shepherd's purse gels. The results investigated that all shepherd's purse gels exhibited shear thinning and elastic characteristics. Increasing the galactomannan concentration could improve the viscosity, G', G", gel strength and water holding capacity (WHC) of the shepherd's purse gels, and reduce their fluidity and shear recovery property. Gel added with LBG had the lowest viscosity, WHC and worst printing formability. The addition of GG made the gel network structure denser and smoother. Gels added with GG, FG and TG at 6 % had high resolution and printing performance. When the gel was added with 6 % of GG, the printing accuracy and stability were 97.30 % and 94.87 %, respectively. The addtion of galactomannan had no impact on the taste characteristics of shepherd's purse gels, while the aroma response values of printed objects containing TG, GG and FG showed increasing trends with the concentration increased. Therefore, this research introduced a novel scheme for 3D printed vegetables.

Development of special nutritional balanced food 3D printing products based on the mixing of animals/plants materials: research progress, applications, and trends

Food 3D printing brings food processing technology into the digital age. This is a vast field that can provide entertainment experience, personalized food and specific nutritional needs. However, the limited availability of suitable food raw materials has restricted the extensive use of 3D food printing processing technique. The search for novel nutritious and healthy food materials that meet the demand for 3D food printing processing technology is core of the sustainable development of this emerging technology. The printing mechanism, precise nutrition, future outlooks and challenges of 3D food printing technology application in hybrid plant and animal food materials are also analyzed.The results demonstrate that selecting suitable animal and plant materials and mixing them into 3D food printing ingredients without adding food additives can result in printable inks, which can also improve the nutritive value and eating quality of 3D food printed products. Sustainability of novel food materials such as animal cell culture meat and microbial protein mixed with conventional food materials to realize 3D printed food can be a potential research direction. Some other issues should also be considered in future research, such as evaluation of the nutritional efficacy of the product, product stability, shelf life, production efficiency and convenience of process operation.

Plant protein edible inks: Upgrading from 3D to 4D food printing

The utilization of plant proteins to formulate edible inks for 3D/4D food printing applications may help address challenges linked to food sustainability, personalized nutrition, and security. We investigate the suitability of various plant proteins for this purpose, including their molecular, functional, and nutritional attributes. Furthermore, we examine the potential of plant protein-based edible inks in 4D printing applications, where the shape or other properties of a material change over time, enabling controlled release profiles and texture modulations. We also discuss the environmental implications, regulatory considerations, and consumer acceptance of plant-based 3D/4D printed foods. Pea and soy proteins are widely used as inks for 3D/4D food printing applications due to their excellent structure-forming abilities, as well as their functional and nutritional properties. However, solely plant protein-based inks often lack essential characteristics required for optimal performance. Their properties can be enhanced by incorporating other food ingredients, such as polysaccharides and polyphenols. As this emerging field holds promise for addressing multiple global food-related challenges, it necessitates interdisciplinary collaboration and ongoing research to unlock its full potential.

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.

Characteristics of Food Printing Inks and Their Impact on Selected Product Properties

Three-dimensional printing, or additive manufacturing, produces three-dimensional objects using a digital model. Its utilisation has been observed across various industries, including the food industry. Technology offers a wide range of possibilities in this field, including creating innovative products with unique compositions, shapes, and textures. A significant challenge in 3D printing is the development of the optimal ink composition. These inks must possess the appropriate rheology and texture for printing and meet nutritional and sensory requirements. The rheological properties of inks play a pivotal role in the printing process, influencing the formation of stable structures. This article comprehensively characterises food inks, distinguishing two primary categories and their respective subgroups. The first category encompasses non-natively extrudable inks, including plant-based inks derived from fruits and vegetables and meat-based inks. The second category comprises natively extrudable inks, encompassing dairy-based, hydrogel-based, and confectionary-based inks. The product properties of rheology, texture, fidelity, and printing stability are then discussed. Finally, the innovative use of food inks is shown.

Improvement of Undaria pinnatifida Sugar-Free Gummy Jellies' Properties by Phycocyanin Under Ultraviolet (UV) Irradiation

In this study, Undaria pinnatifida (UP) was used as the primary research material, and sugar-free gummy jelly was prepared using ultraviolet (UV) irradiation with phycocyanin. The properties were measured using a texture analyzer, color difference analyzer, low-field nuclear magnetic resonance (LF-NMR) analyzer, and sensory evaluation. Additionally, the stability during accelerated storage was examined. The results showed that UV irradiation-assisted phycocyanin significantly increased the hardness of the sugar-free gummy jelly, from 268.4 ± 11.0 g to 477.9 ± 5.2 g, and enhanced its chewiness, from 247.4 ± 12.2 to 415.1 ± 3.1. Additionally, the jelly exhibited stronger water binding ability, with the proportion of immovable water increasing from 6.17 ± 0.66% to 9.52 ± 0.77%. During accelerated storage, the texture properties, color, water migration, and phycocyanin content of the sugar-free gummy jelly were changed. However, UV irradiation-assisted phycocyanin treatment slowed down the changes in the texture, color, and phycocyanin content of the sugar-free gummy jelly, which indicated that the product had good stability during storage. These results enhance the application of UP in sugar-free gummy jellies.

Technological advances in protein extraction, structure improvement and assembly, digestibility and bioavailability of plant-based foods

Plant-based foods are being considered seriously to replace traditional animal-origin foods for various reasons. It is well known that animals release large amounts of greenhouse gases into the environment during feeding, and eating animal-origin foods may also cause some health problems. Moreover, animal resources will likely be in short supply as the world population grows. It is highly likely that serious health problems ascribed to insufficient protein intake in some areas of the world will occur. Studies have shown that environmentally friendly, abundant, and customizable plant-based foods can be an effective alternative to animal-based foods. However, currently, available plant-based foods lack nutrients unique to animal-based foods. Innovative processing technologies are needed to improve the nutritional value and functionality of plant-based foods and make them acceptable to a wider range of consumers. Therefore, protein extraction technologies (e.g., high-pressure extraction, ultrasound extraction, enzyme extraction, etc.), structure improvement and assembly technologies (3D printing, micro-encapsulation, etc.), and technologies to improve digestibility and utilization of bioactive substances (microbial fermentation, physical, etc.) in the field of plant-based foods processing are reviewed. The challenges of plant-based food processing technologies are summarized. The advanced technologies aim to help the food industry solve production problems using efficient, environmentally friendly, and economical processing technologies and to guide the development of plant-based foods in the future.

A novel fucoxanthin enriched seaweed gummy: Physicochemical qualities and protective effect on UVB-induced retinal müller cells

Retinal disease has become the major cause of visual impairment and vision loss worldwide. Carotenoids, which have the potential antioxidant and eye-care activities, have been widely used in functional foods. Our previous study showed that fucoxanthin could exert photoprotective activity in UVB-induced retinal müller cells (RMCs). To extend the application of fucoxanthin in food industry, fucoxanthin, Undaria pinnatifida pulp (UPP), carrageenan, and other ingredients were mixed to prepare seaweed-flavoured photoprotective gummies in this study. The structural and functional properties of the gummies were then evaluated by physicochemical test and cell experiments. As a result, fucoxanthin enriched gummies presented favourable structural properties and flavour. The hydroxyl groups in fucoxanthin and κ-carrageenan are bonded through hydrogen bonds, forming the spatial network structure inside the gummies, enhancing its elasticity. The gummies showed significant antioxidant effect and alleviated the UVB oxidation damage in RMCs. Moreover, the main ingredients carrageenan and UPP improved the stability of fucoxanthin during in vitro digestion. The results enhance the application of fucoxanthin in functional food with photoprotective activity.

Unconventional sourced proteins in 3D and 4D food printing: Is it the future of food processing?

Following consumer trends and market needs, the food industry has expanded the use of unconventional sources to obtain proteins. In parallel, 3D and 4D food printing have emerged with the potential to enhance food processing. While 3D and 4D printing technologies show promising prospects for improving the performance and applicability of unconventional sourced proteins (USP) in food, this combination remains relatively unexplored. This review aims to provide an overview of the application of USP in 3D and 4D printing, focusing on their primary sources, composition, rheological, and technical-functional properties. The drawbacks, challenges, potentialities, and prospects of these technologies in food processing are also examined. This review underscores the current necessity for greater regulation of food products processed by 3D and 4D printing. The data presented here indicate that 3D and 4D printing represent viable, sustainable, and innovative alternatives for the food industry, emphasizing the potential for further exploration of 4D printing in food processing. Additional studies are warranted to explore their application with unconventional proteins.

Effect of plasma-activated water on the quality of wheat starch gel-forming 3D printed samples

In this study, a new method for preparing gels suitable for 3D printing of food structures using wheat starch and plasma activated water (PAW) is presented. The investigation focused on the effect of PAW on starch pasting and the final 3D printed product. It was found that the use of PAW for 15 min in the preparation of wheat starch gels optimized carrier stability and improved height retention in the printed constructs, showing significant shape retention even after prolonged storage. This durability can be attributed to the hindrance of polymerization between starch molecules and the promotion of intermolecular starch polymerization when reactive groups and ions are integrated into the starch structure. The incorporation of PAW with soluble reactive groups, ions and acidity not only accelerates the breakdown of the starch molecules but also facilitates additional hydrogen bonding within the double helix, which strengthens the structure of the gel. This interaction accelerates the retrogradation of the starch, thereby enhancing its overall stability. This study provides a new green approach to modify the 3D printing properties of starch gels.

Effect of dielectric barrier discharge (DBD) plasma treatment on physicochemical and 3D printing properties of wheat starch

In recent years, the focus has shifted towards carbohydrate-based hydrogels and their eco-friendly preparation methods. This study involved an investigation into the treatment of wheat starch using dielectric barrier discharge (DBD) plasma technology over varying time gradients (0, 2, 5, 10, 15, and 20 min). The objective was to systematically examine the impact of different treatment durations on the physicochemical properties of wheat starch and the suitability of its gels for 3D printing. Morphology of wheat starch remained intact after DBD treatment. However, it led to a reduction in the amylose content, molecular weight, and crystallinity. This subsequently resulted in a decrease in the pasting temperature and viscosity. Moreover, the gels of the DBD-treated starch exhibited superior 3D printing performance. After a 2-min DBD treatment, the 3D printed samples of the wheat starch gel showed no significant improvements, as broken bars were evident on the surface of the 3D printed graphic, whereas DBD-20 showed better printing accuracy and surface structure, compared to the original starch without slumping. These results suggested that DBD technology holds potential for developing new starch-based gels with impressive 3D printing properties.

Personalized nutrition with 3D-printed foods: A systematic review on the impact of different additives

Three-dimensional (3D) printing is one of the world's top novel technologies in the food industry due to the production of food in different conditions and places (restaurants, homes, catering, schools, for dysphagia patients, and astronauts' food) and the production of personalized food. Nowadays, 3D printers are used in the main food industries, including meat, dairy, cereals, fruits, and vegetables, and have been able to produce successfully on a small scale. However, due to the expansion of this technology, it has challenges such as high-scale production, selection of printable food, formulation optimization, and food production according to the consumer's opinion. Food additives (gums, enzymes, proteins, starches, polyphenols, spices, probiotics, algae, edible insects, oils, salts, vitamins, flavors, and by-products) are one of the main components of the formulation that can be effective in food production according to the consumer's attitude. Food additives can have the highest impact on textural and sensory characteristics, which can be effective in improving consumer attitudes and reducing food neophobia. Most of the 3D-printed food cannot be printed without the presence of hydrocolloids, because the proper flow of the selected formulation is one of the key factors in improving the quality of the printed product. Functional additives such as probiotics can be useful for specific purposes and functional food production. Food personalization for specific diseases with 3D printing technology requires a change in the formulation, which is closely related to the selection of correct food additives. For example, the production of 3D-printed plant-based steaks is not possible without the presence of additives, or the production of food for dysphagia patients is possible in many cases by adding hydrocolloids. In general, additives can improve the textural, rheological, nutritional, and sensory characteristics of 3D printed foods; so, investigating the mechanism of the additives on all the characteristics of the printed product can provide a wide perspective for industrial production and future studies.

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.

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.

3D/4D printed super reconstructed foods: Characteristics, research progress, and prospects

Super reconstructed foods (SRFs) have characteristics beyond those of real system in terms of nutrition, texture, appearance, and other properties. As 3D/4D food printing technology continues to be improved in recent years, this layered manufacturing/additive manufacturing preparation technology based on food reconstruction has made it possible to continuously develop large-scale manufacture of SRFs. Compared with the traditional reconstructed foods, SRFs prepared using 3D/4D printing technologies are discussed comprehensively in this review. To meet the requirements of customers in terms of nutrition or other characteristics, multi-processing technologies are being combined with 3D/4D printing. Aspects of printing inks, product quality parameters, and recent progress in SRFs based on 3D/4D printing are assessed systematically and discussed critically. The potential for 3D/4D printed SRFs and the need for further research and developments in this area are presented and discussed critically. In addition to the natural materials which were initially suitable for 3D/4D printing, other derivative components have already been applied, which include hydrogels, polysaccharide-based materials, protein-based materials, and smart materials with distinctive characteristics. SRFs based on 3D/4D printing can retain the characteristics of deconstruction and reconstruction while also exhibiting quality parameters beyond those of the original material systems, such as variable rheological properties, on-demand texture, essential printability, improved microstructure, improved nutrition, and more appealing appearance. SRFs with 3D/4D printing are already widely used in foods such as simulated foods, staple foods, fermented foods, foods for people with special dietary needs, and foods made from food processingbyproducts.

Impact of Corn Starch Molecular Structures on Texture, Water Dynamics, Microstructure, and Protein Structure in Silver Carp (Hypophthalmichthys molitrix) Surimi Gel

This study systematically investigates the impact of corn starch molecular structures on the quality attributes of surimi gel products. Employing molecular analyses to characterize corn starch, three amylopectin fractions (A, B1, and B2), categorized by the degree of polymerization ranges (6 < X ≤ 12, 12 < X ≤ 24, and 24 < X ≤ 36, respectively) were specifically focused on. The surimi gel quality was comprehensively assessed through texture profile analysis, nuclear magnetic resonance, scanning electron microscopy, stained section analysis, and Fourier transform infrared spectroscopy. Results indicated the substantial volume expansion of corn amylopectin upon water absorption, effectively occupying the surimi gel matrix and fostering the development of a more densely packed protein network. Starch gels with higher proportions of A, B1, and B2 exhibited improved hardness, chewiness, and bound water content in the resultant surimi gels. The weight-average molecular weight and peak molecular weight of corn starch showed a strong positive correlation with surimi gel hardness and chewiness. Notably, the secondary structure of proteins within the surimi gel was found to be independent of corn starch's molecular structure. This study provides valuable insights for optimizing formulations in surimi gel products, emphasizing the significance of elevated A, B1, and B2 content in corn starch as an optimal choice for crafting dense, chewy, water-retaining surimi gels.

Encapsulation of lutein in gelatin type A/B-chitosan systems via tunable chains and bonds from tweens: Thermal stability, rheologic property and food 2D/3D printability

Lutein could be stabilized in gelatin type A/B-chitosan systems by different polyoxyethylene sorbitan fatty acid esters (tweens) via tunable chains and bonds, and the homogeneous system held potential in food 2D/3D printing. During encapsulation of lutein in gelatin-chitosan matrix complexes, tween 40, tween 60 and tween 80 assisted in the excellent centrifugation stability, freeze-thaw stability, chemical stability as well as thermal stability. The tweens contained systems also possessed excellent rheological properties, including shearing thinning property, self-supporting characteristics, and favorable thixotropy. Especially, tween 80 performed well in facilitating the stability and rheological properties of systems with uniform micromorphology due to its long alkyl chains and carbon-carbon double bonds (two sp2 hybridized C-atoms) (from FTIR, XRD, SEM, etc.); and gelatin type B illustrated higher protection effects on lutein because of its strong electrostatic interaction with chitosan. The optimal systems could work as edible ink for 2D/3D printing on food with great UV-irradiation stability and high definition. Surimi could be modified by the optimal complex and possessed excellent shear-thinning property, proper yield stress, low dependence on frequency and stable structure, which was successfully applied for innovative 3D printing with sophisticated shapes. The practical food 2D/3D printing (like bread and surimi) demonstrated high potential in food creation and food innovation.

Recent insights on advancements and substantial transformations in food printing technology from 3 to 7D

Food printing using 3D, 4D, and 5D printing processes has received a lot of interest as a result of rising living standards and increased customer desire for new foods. In the food industry, 3D as well as 4D printing are extremely effective methods for additive manufacturing. The 3D printing technology produces flat objects with a variety of mechanical strengths. The strength of the object depends on the type of material used and the printing process. Printing structures with the most complex geometric, such as curved surfaces, necessitates the usage of supplementary material. The 4D printing procedure necessitates additional stimuli in order to adjust the aspect of the generated geometry. These obstacles can be addressed by employing 5D printing techniques, which prints the product in three motions and two rotational axes without the use of additional support material. These emerging innovations are likely to result in substantial advancements in all industries, including the manufacturing of high-quality food products. Food printing technology can be used to create long shelf-life products by printing food with protective coatings that prevent oxidation and degradation. Foods can also be printed in specific shapes or sizes to reduce surface area exposed to air. 6D printed objects can be created as a result of 5D printing because it is regarded as a by-product of 5D printing technology. 6D printing can save time and money by using the right processing parameters to create strong materials that are more sensitive to stimuli. 7D printing can enable more efficient production processes, reduce costs, and enable the development of products that are more complex and intricate than what is achievable with traditional manufacturing methods. The revolutionary change brought by food printing technologies in the field of applications, research and development, processing, advantages in food industry have been discussed in this paper.

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.

Recent advances on natural colorants-based intelligent colorimetric food freshness indicators: fabrication, multifunctional applications and optimization strategies

With the increasing concerns of food safety and public health, tremendous efforts have been concentrated on the development of effective, reliable, nondestructive methods to evaluate the freshness level of different kinds of food. Natural colorants-based intelligent colorimetric indicators which are typically constructed with natural colorants and polymer matrices has been regarded as an innovative approach to notify the customers and retailers of the food quality during the storage and transportation procedure in real-time. This review briefly elucidates the mechanism of natural colorants used for intelligent colorimetric indicators and fabrication methodologies of natural colorants-based food freshness indicators. Subsequently, their multifunctional applications in intelligent food packaging systems like antioxidant packaging, antimicrobial packaging, biodegradable packaging, UV-blocking packaging and inkless packaging are well introduced. This paper also summarizes several optimizing strategies for the practical application of this advanced technology from different perspectives. Strategies like adopting a hydrophobic matrix, constructing double-layer film and encapsulation have been developed to improve the stability of the indicators. Co-pigmentation, metal ion complexation, pigment-mixing and using substrates with high surface area are proved to be effective to enhance the sensitivity of the indicators. Approaches include multi-index evaluation, machine learning and smartphone-assisted evaluation have been proven to improve the accuracy of the intelligent food freshness indicators. Finally, future research opportunities and challenges are proposed. Based on the fundamental understanding of natural colorants-based intelligent colorimetric food freshness indicators, and the latest research and findings from literature, this review article will help to develop better, lower cost and more reliable food freshness evaluation technique for modern food industry.

Four-Dimensional Micro/Nanorobots via Laser Photochemical Synthesis towards the Molecular Scale

Miniaturized four-dimensional (4D) micro/nanorobots denote a forerunning technique associated with interdisciplinary applications, such as in embeddable labs-on-chip, metamaterials, tissue engineering, cell manipulation, and tiny robotics. With emerging smart interactive materials, static micro/nanoscale architectures have upgraded to the fourth dimension, evincing time-dependent shape/property mutation. Molecular-level 4D robotics promises complex sensing, self-adaption, transformation, and responsiveness to stimuli for highly valued functionalities. To precisely control 4D behaviors, current-laser-induced photochemical additive manufacturing, such as digital light projection, stereolithography, and two-photon polymerization, is pursuing high-freeform shape-reconfigurable capacities and high-resolution spatiotemporal programming strategies, which challenge multi-field sciences while offering new opportunities. Herein, this review summarizes the recent development of micro/nano 4D laser photochemical manufacturing, incorporating active materials and shape-programming strategies to provide an envisioning of these miniaturized 4D micro/nanorobots. A comparison with other chemical/physical fabricated micro/nanorobots further explains the advantages and potential usage of laser-synthesized micro/nanorobots.

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.

Bulk Polymerization of Thermoplastic Shape Memory Epoxy Polymer for Recycling Applications

Conventional epoxy polymers are thermo-set and difficult to recycle and reuse. In this study, a series of linear thermoplastic epoxy polymers (EPx) with shape memory properties were prepared by using a bifunctional monoamine diglycolamine (DGA) as a curing agent and an equivalent amount of bifunctional rigid epoxy resin (E-51) and bifunctional flexible epoxy resin (polypropylenglycol diglycidyl ether, PPGDGE) in a bulk polymerization reaction. The results showed that these samples can fully react under the curing process of, 60 °C/2 h, followed by 80 °C/2 h, followed by 120 °C/2 h. The introduction of different contents of PPGDGE can adjust the T_g of the material to adapt to different environmental requirements, and can significantly increase the fracture strain of the material and improve its micro-phase separation structure. Thus, R_f of the material is close to 100%, and R_r is increased from 87.98% to 97.76%. Importantly, this linear chain structure allows the material to be easily recycled and reprocessed by dissolving or melting, and also means the material shows potential for 3D printing or other thermoplastic remolding.

3D printing based on meat materials: Challenges and opportunities

Three-dimensional (3D) printing, as an emerging technology, is driving great progress in the food industry. In the meat field, 3D printing is expected to replace the traditional food industry and solve the problems of raw material waste and food contamination. Nevertheless, the application of 3D printing in meat still faces many challenges. The rheological properties of the ink, such as shear thinning behavior, viscosity, and yield stress, are critical in determining whether it can be printed smoothly and ensuring the quality of the product. Meat materials are complex multi-phase colloidal systems with unique fibrous structures that cannot be printed directly, and improving the printability of meat colloids mainly limits meat printing. The complexity of meat colloidal systems determines the different heat requirements. In addition, at this stage, the functionality of the printer and the formulation of a single nutritional and organoleptic properties limit the implementation and application of 3D printing. Moreover, the development of cultured meat, the full application of by-products, and the emergence of new technologies provides opportunities for the application of 3D printing in the meat industry. This review highlights the current challenges and opportunities for the application of 3D printing in meat to provide new ideas for the development of 3D printing.

Consumer acceptance of new food trends resulting from the fourth industrial revolution technologies: A narrative review of literature and future perspectives

The growing consumer awareness of climate change and the resulting food sustainability issues have led to an increasing adoption of several emerging food trends. Some of these trends have been strengthened by the emergence of the fourth industrial revolution (or Industry 4.0), and its innovations and technologies that have fundamentally reshaped and transformed current strategies and prospects for food production and consumption patterns. In this review a general overview of the industrial revolutions through a food perspective will be provided. Then, the current knowledge base regarding consumer acceptance of eight traditional animal-proteins alternatives (e.g., plant-based foods and insects) and more recent trends (e.g., cell-cultured meat and 3D-printed foods) will be updated. A special focus will be given to the impact of digital technologies and other food Industry 4.0 innovations on the shift toward greener, healthier, and more sustainable diets. Emerging food trends have promising potential to promote nutritious and sustainable alternatives to animal-based products. This literature narrative review showed that plant-based foods are the largest portion of alternative proteins but intensive research is being done with other sources (notably the insects and cell-cultured animal products). Recent technological advances are likely to have significant roles in enhancing sensory and nutritional properties, improving consumer perception of these emerging foods. Thus, consumer acceptance and consumption of new foods are predicted to continue growing, although more effort should be made to make these food products more convenient, nutritious, and affordable, and to market them to consumers positively emphasizing their safety and benefits.

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.

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.

Determination of color formation of multicomponent fruit and vegetable pastes and dried powder fractions during low temperature treatment

The aim of the work is to determine the color formation of multicomponent fruit and vegetable pastes and dried powder fractions at the stages of low-temperature pre-concentration and drying, as one of the factors, maintaining the quality of the products. In the production of organic plant semi-finished products an important factor is the implementation of high-quality technological operations, including heat and mass transfer, which affects the final organoleptic characteristics of products. It is important to take into account the color of raw materials at the stages of blending puree in the production of paste and powder semi-finished products, which requires the introduction of a unified method for assessing the color of raw materials at each stage of the technological operation. An analysis of traditional methods for determining color formation has been performed, as a result of which it has been found, that the most effective method of evaluation is digital, based on photo processing of the prototype. According to this method, the evaluation of color formation in the manufacture of semi-finished fruits and vegetables in accordance with the proposed recipes has been conducted. Color indices of multicomponent pastes and dried fractions based on them for three prototypes were obtained. The brightness of all samples of pastes is in the range - 36.4… 37.0 % with a purity of tone 64.7… 78.2 %, which corresponds to the reddish-orange color, was obtained. After drying the test samples of pastes to the dried fraction, it has been found, that the brightness, depending on the percentage of raw materials in a sample falls in the range of 30.5… 33.2 %, at that the coloration corresponds to colors from bluish-purple to bluish-red with a purity of tone within 34.7… 34.9 %. As a result of evaluation of organoleptic indicators, it has been found, that according to the presented research samples, the best indicators have a sample with 40 % of raw apples, 20 % of pumpkin, 30 % of cranberries and 10 % of hawthorn. The obtained research data will be useful in the development of methods for the production of semi-finished products from vegetable raw materials. The applied digital method of color determination differs in simplicity and economy in comparison with colorimetric and spectrometric

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.

Trends in functional food development with three-dimensional (3D) food printing technology: prospects for value-added traditionally processed food products

One of the recent, innovative, and digital food revolutions gradually gaining acceptance is three-dimensional food printing (3DFP), an additive technique used to develop products, with the possibility of obtaining foods with complex geometries. Recent interest in this technology has opened the possibilities of complementing existing processes with 3DFP for better value addition. Fermentation and malting are age-long traditional food processes known to improve food value, functionality, and beneficial health constituents. Several studies have demonstrated the applicability of 3D printing to manufacture varieties of food constructs, especially cereal-based, from root and tubers, fruit and vegetables as well as milk and milk products, with potential for much more value-added products. This review discusses the extrusion-based 3D printing of foods and the major factors affecting the process development of successful edible 3D structures. Though some novel food products have emanated from 3DFP, considering the beneficial effects of traditional food processes, particularly fermentation and malting in food, concerted efforts should also be directed toward developing 3D products using substrates from these conventional techniques. Such experimental findings will significantly promote the availability of minimally processed, affordable, and convenient meals customized in complex geometric structures with enhanced functional and nutritional values.