3D food printing is the process of manufacturing food products using a variety of additive manufacturing techniques. Most commonly, food grade syringes hold the printing material, which is then deposited through a food grade nozzle layer by layer. The most advanced 3D food printers have pre-loaded recipes on board and also allow the user to remotely design their food on their computers, phones or some IoT device. The food can be customized in shape, color, texture, flavor or nutrition, which makes it very useful in various fields such as space exploration and healthcare.

History

General principles

There are three general areas that impact precise and accurate food printing: materials/ingredients (viscosity, powder size), process parameters (nozzle diameter, printing speed, printing distance), and post-processing methods (baking, microwaving, frying).

Materials and ingredients

The type of food available to print is limited by the printing technique.Sun, J., Peng, Z., Zhou, W., Fuh, J. Y., Hong, G. S., & Chiu, A. (2015). A review on 3D printing for customized food fabrication. ''Procedia Manufacturing'', ''1'', 308-319. For an overview of these printing techniques, please see the section ''Printing Techniques'' below:

Extrusion-based printing ingredients

Common ingredients used in extrusion based printing are inherently soft enough to extrude from a syringe/printhead and possess a high enough

viscosity The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the inte ...

to retain a shape.Cohen, D. L., Lipton, J. I., Cutler, M., Coulter, D., Vesco, A., & Lipson, H. (2009, August). Hydrocolloid printing: a novel platform for customized food production. In ''Solid Freeform Fabrication Symposium'' (pp. 807-818). Austin, TX. In certain cases, powdered ingredients (protein, sugar, etc.) are added to increase viscosity, e.g. adding flour to water creates a paste that can be printed. Inherently soft materials include: *

purée A purée (or mash) is cooked food, usually vegetables, fruits or legumes, that has been ground, pressed, blended or sieved to the consistency of a creamy paste or liquid. Purées of specific foods are often known by specific names, e.g., apples ...

* jelly * frosting * cheese * mashed potatoes Certain ingredients that are solid can be used by melting and then extruding the ingredient, e.g. chocolate.

Selective laser sintering and binder jetting ingredients

Powdered ingredients: *sugar *chocolate powder *protein powder

Inkjet printing ingredients

Ingredients with low

are used for surface filling: * sauces (pizza, hot sauce, mustard, ketchup, etc.) * colored food ink

Printing techniques

Extrusion-based printing

Although there are different approaches to extrusion based printing, these approaches follow the same basic procedures. The platform on which food is printed consists of a standard 3-axis stage with a computer controlled extrusion head. This extrusion head pushes food materials through a nozzle typically by way of compressed air or squeezing. The nozzles can vary with respect to what type of food is being extruded or the desired printing speed (typically the smaller the nozzle the longer the food printing will take). As the food is printed, the extrusion head moves along the 3-axis stage printing the desired food. Some printed food requires additional processing such as baking or frying before consumption. Extrusion based food printers can be purchased for household use, are typically compact in size, and have a low maintenance cost. Comparatively, extrusion based printing provides the user with more material choices. However, these food materials are usually soft, and as a result, makes printing complex food structures difficult. In addition, long fabrication times and deformations due to temperature fluctuations with additional baking or frying require further research and development to overcome.

Hot-melt and room temperature

In Hot-melt extrusion, the extrusion head heats the food material slightly above the material's melting point. The melted material is then extruded from the head and then solidifies soon thereafter. This allows the material to be easily manipulated into the desired form or model. Foods such as chocolate are used in this technique because of its ability to melt and solidify quickly.Hao, L., Mellor, S., Seaman, O., Henderson, J., Sewell, N., & Sloan, M. (2010). Material characterization and process development for chocolate additive layer manufacturing. ''Virtual and Physical Prototyping'', ''5''(2), 57-64. Other food materials do not inherently require a heating element in order to be printed. Food materials such as jelly, frosting, puree, and similar food materials with appropriate viscosity can be printed at room temperature without prior melting.

Selective laser sintering

selective laser sintering Selective laser sintering (SLS) is an additive manufacturing (AM) technique that uses a laser as the power and heat source to sinter powdered material (typically nylon or polyamide), aiming the laser automatically at points in space defined ...

, powdered food materials are heated and bonded together forming a solid structure. This process is completed by bonding the powdered material layer by layer with a laser as the heat source. After a layer is completed with the desired areas bonded, it is then covered by a new unbonded layer of powder. Certain parts of this new unbonded layer are heated by the laser in order to bond it with the structure. This process continues in a vertical upwards manner until the desired food model is constructed. After construction, unbonded material can then be recycled and used to print another food model. Selective laser sintering enables the construction of complex shapes and models and the ability to create different food textures. It is limited by the range of suitable food materials, namely powdered ingredients.CandyFab (2007). The CandyFab project. Available at http://wiki. candyfab.org/Main_Page. Accessed Dec 2019 Due to this limitation, selective laser sintering has been used primarily for creating sweets/candies.

Binder jetting

Similarly to selective laser sintering, binder jetting uses powdered food materials to create a model layer by layer. Instead of using heat to bond the materials together, a liquid binder is used. After bonding the desired areas of a layer, a new layer of powder is then spread over the bonded layer covering it. Certain parts of this new layer are then bonded to the previous layer. The process is repeated until the desired food model is constructed. As with selective laser sintering, binder jetting enables the construction of complex shapes and models and the ability to create different food textures.Southerland, D., Walters, P., & Huson, D. (2011, January). Edible 3D printing. In ''NIP & Digital Fabrication Conference'' (Vol. 2011, No. 2, pp. 819-822). Society for Imaging Science and Technology. Likewise, it is also limited by the range of suitable food materials, namely powdered ingredients.

Inkjet printing

Inkjet printing is used for surface filling or image decoration.Foodjet (2012). Foodjet. Available at: http://foodjet.nl/. Accessed Dec 2019 By utilizing gravity, edible food ink is dropped onto the surface of the food, typically a cookie, cake, or other candy. This is a non-contact method, hence the printhead does not touch the food protecting the food from contamination during image filling. The ink droplets may consist of a broad range of colors allowing users to create unique and individualized food images.Pallottino, F., Hakola, L., Costa, C., Antonucci, F., Figorilli, S., Seisto, A., & Menesatti, P. (2016). Printing on food or food printing: a review. ''Food and Bioprocess Technology'', ''9''(5), 725-733. An issue with inkjet printing is the food materials being incompatible with the ink resulting in no image or high image distortion. Inkjet printers can be purchased for household or commercial use, and industrial printers are suitable for mass production.

Multi-printhead and multi-material

In multi-printhead and multi-material printing, multiple ingredients are printed at the same time or in succession.Lipton, J., Arnold, D., Nigl, F., Lopez, N., Cohen, D. L., Norén, N., & Lipson, H. (2010, August). Multi-material food printing with complex internal structure suitable for conventional post-processing. In ''Solid Freeform Fabrication Symposium'' (pp. 809-815). There are different ways to support multi-material printing. In one instance, multiple printheads are used to print multiple materials/ingredients, as this can speed up production, efficiency, and lead to interesting design patterns. In another instance, there is one printhead, and when a different ingredient is required, the printer exchanges the material being printed. Multiple materials/ingredients equates to a more diverse range of meals available to print, a broader nutritional range, and is quite common for food printers.

Post-processing

In the post-processing phase, printed food may require additional steps before consumption. This includes processing activities such as baking, frying, cleaning, etc. This phase can be one of the most critical to 3D printed food, as the printed food needs to be safe for consumption. An additional concern in post processing is the deformation of the printed food due to the strain of these additional processes. Current methods involve trial and error. That is, combining food additives with the materials/ingredients to improve the integrity of complex structures and to ensure the printed structure retains its shape. Additives such as

transglutaminase Transglutaminases are enzymes that in nature primarily catalyze the formation of an isopeptide bond between γ-carboxamide groups ( -(C=O)NH2 ) of glutamine residue side chains and the ε-amino groups ( -NH2 ) of lysine residue side cha ...

and hydrocolloids have been added to ingredients in order to help retain the printed shape while printing and after cooking. Additionally, recent research has produced
visual simulation
for baking breads, cookies, pancakes and similar materials that consist of dough or batter (mixtures of water, flour, eggs, fat, sugar and leavening agents). By adjusting certain parameters in the simulation, it shows the realistic effect that baking will have on the food. With further research and development, a visual simulation of 3D printed foods being cooked could predict what is vulnerable to deformation.

Applications

Personal nutrition

Personalized dietary requirements for an individual's nutritional needs has been linked to the prevention of diseases. As such, eating nutritious food is paramount to living a healthy life. 3D printed food can provide the control necessary to put a custom amount of protein, sugar, vitamins, and minerals into the foods we consume. Another area in customized food, is elderly nutrition. The elderly sometimes cannot swallow foods, and as such require a softer pallet. However, these foods are often unappealing causing some individuals not to eat what their bodies' nutritional needs require. 3D printed food can provide a soft and aesthetically pleasing food in which the elderly can consume their bodies' dietary requirements. In October 2019, startup company ''Nourished'' 3D prints personalized nutritional gummies from 28 different vitamins. Individuals take a survey, then based on their answers, a personalized nutritional gummy is printed for that individual.

Sustainability and solution for hunger

As the world's population continues to grow, experts believe that current food supplies will not be able to supply the population. Thus, a sustainable food source is critical. Studies have shown that

entomophagy Entomophagy (, from Greek ἔντομον ', 'insect', and φαγεῖν ', 'to eat') is the practice of eating insects. An alternative term is insectivory. Terms for organisms that practice entomophagy are ''entomophage'' and ''insectivore' ...

, the consumption of insects, has the potential to sustain a growing population.Van Huis, A. (2013). Potential of insects as food and feed in assuring food security. ''Annual review of entomology'', ''58'', 563-583. Insects such as crickets require less feed, less water, and provide around the same amount of protein that chickens, cows, and pigs do. Crickets can be ground into a protein flour. In one study, researchers provide an overview of the process of 3D printing insect flour into foods that do not resemble insects; thus, keeping the nutritional value of the insect intact.

Space exploration

As humans begin venturing into space for a longer time, the nutritional requirements for maintaining crew health is critical. Currently

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

is exploring ways of integrating 3D printing food into space in order to sustain the crew's dietary requirements. The vision is to 3D print powdered food layers that have a shelf life of 30 years instead of using traditional freeze dried food that have a shelf life of 5 years. In addition to dietary requirements, 3D printing food in space could provide a morale boost, as the astronauts would be able to design custom meals that are aesthetically pleasing. In September 2019, Russian cosmonauts, along with Israeli startup Aleph Farms, grew meat from cow cells, then 3D printed the cells into steaks.

Meat bioprinting

Livestock farming is one of the top contributors to deforestation,

land degradation Land degradation is a process in which the value of the biophysical environment is affected by a combination of human-induced processes acting upon the land. It is viewed as any change or disturbance to the land perceived to be deleterious ...

, water pollution and desertification. Among other reasons, this has led to the new promising technology of meat bioprinting. One alternative to livestock farming is cultured meat, also known as lab-grown meat.

Cultured meat Cultured meat (also known by other names) is meat produced by culturing animal cells ''in vitro''. It is a form of cellular agriculture. Cultured meat is produced using tissue engineering techniques pioneered in regenerative medicine. Jason M ...

is produced by taking a small biopsy from animals, extracting the

myosatellite cell Myosatellite cells, also known as satellite cells, muscle stem cells or MuSCs, are small multipotent cells with very little cytoplasm found in mature muscle. Satellite cells are precursors to skeletal muscle cells, able to give rise to satellite ...

s and adding growth serum to multiply the cells. The resulting product is then used as a material for bioprinting meat. The post-processing phase, among other steps, includes adding flavour, vitamins and iron to the product. Yet another alternative is printing a

meat analogue A meat alternative or meat substitute (also called plant-based meat or fake meat, sometimes pejoratively) is a food product made from vegetarian or vegan ingredients, eaten as a replacement for meat. Meat alternatives typically approximate qua ...

Novameat Novameat is a food tech startup that works with plant-based foods, including plant-based meat substitutes. According to ''El País'', the company was responsible in 2018 for creating a meat substitute through 3D printing, whereby a plant-based ...

, a Spanish startup has been able to print a plant-based steak and mimic the texture and appearance of real meat.

Creative food design

Food presentation and food appearance customization for individuals is a big trend in the food industry. So far food customization and creative designs have required hand-made skills, which results in low production rate and high cost. 3D food printing can overcome this problem by providing the necessary tools for creative food design even for home users. 3D food printing has enabled some intricate designs which cannot be accomplished with traditional food manufacturing. Brand logos, text, signatures, pictures can now be printed on some food products like pastries and coffee. Complex geometric shapes have also been printed, mainly using sugar. With 3D printing, chefs can now turn their visual inspirations into signature culinary creations. Another benefit is being able to print nutritious meals in shapes that appeal to children.

Reduced food waste

Worldwide, one third of the total food produced for consumption, around 1.6 billion tons per year, goes to waste.

Food waste Food loss and waste is food that is not eaten. The causes of food waste or loss are numerous and occur throughout the food system, during production, processing, distribution, retail and food service sales, and consumption. Overall, about o ...

happens during processing, distribution and consumption. 3D food printing is a very promising way of reducing food waste during the phase of consumption, by utilizing food products like meat off-cuts, distorted fruits and vegetables, sea food by-products and perishables. These products can be processed in a suitable form for printing. Upprinting Food, a Dutch startup, has been blending and combining different ingredients from food waste to create purees which are then used as materials for 3D printing. Chefs are also creating different dishes from leftover food using 3D food printers.

Challenges

Structure

Unlike traditionally prepared food, the variety of food that can be manufactured using 3D printing is limited by the physical characteristics of the materials. Food materials are generally much softer than the weakest plastic used in 3D printing, making the printed structures very fragile. So far, most studies use trial and error as an approach to overcoming this challenge, but scientists are working on developing new methods that are able to predict the behavior of different materials during the printing process. These methods are developed by analyzing the

rheological Rheology (; ) is the study of the flow of matter, primarily in a fluid (liquid or gas) state, but also as "soft solids" or solids under conditions in which they respond with plastic flow rather than deforming elastically in response to an appli ...

properties of the materials and their relation to the printing stability.

Design

When designing a 3D model for a food product, the physical and geometrical limitations of the printing materials should be taken into account. This makes the designing process a very complex task and so far there is no available software that accounts for that. Building such software is also a complex task due to the vast variety of food materials. Considering that personal users who incorporate 3D food printing in their kitchens represent a significant part of the overall users, the design of the software interface adds to the complexity. The interface of such software should be simple and have high

usability Usability can be described as the capacity of a system to provide a condition for its users to perform the tasks safely, effectively, and efficiently while enjoying the experience. In software engineering, usability is the degree to which a soft ...

while still providing enough features and customization options for the user without causing cognitive overload.

Speed

The current speed of 3D printing food could be sufficient for home use, but the process is very slow for mass production. Simple designs take 1 to 2 minutes, detailed designs take 3 to 7 minutes, and more intricate designs take even longer. The speed of printing food is tightly correlated to the rheological properties of the materials. Research shows that high printing speed results in low fidelity samples due to the dragging effect, while very low speed causes instability in material deposition. In order for 3D food printing to find its way to the food industry, the printing speed needs improvement or the cost of such technology should be affordable enough for companies to operate several printers.

Multi-material printing

The color, flavor and texture of food are of crucial importance when fabricating an edible product, thus in most cases it is required that a food printer supports multi-material printing. The current available 3D food printers are limited to using a few different materials due to the challenge of developing multiple extruder capabilities. This limits the variety of food products that can be 3D printed, leaving out complex dishes that require a lot of different materials.

Safety

When 3D printing food, the safety is very crucial. A food printer must ensure safety along the entire path taken by the food material. Due to the possibility of food getting stuck somewhere along the path, bacteria accumulation is a major concern. Microbial stability is a crucial parameter of the quality of the printed food, thus it needs to be addressed both during the design of the printer and during the printing process. On the other hand, the materials that come into contact with the food may not be as significant of a concern since high quality printers use stainless steel and BPA-free materials.

Copyright

Existing food products in the market such as chocolates in various shapes could easily be scanned and the obtained 3D models could be used to replicate those products. These 3D models could then be disseminated via Internet leading to copyright infringement. There are laws regulating copyright issues but it is not clear whether they will be sufficient to cover all aspects of a field like 3D food printing.

References

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