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3D Food Printing is the process of manufacturing food products using 3D printing techniques. 3D food printers use food grade syringes to hold the printing material, which is then deposited through a food grade nozzle layer by layer, in an automated additive manner onto the printing surface. The most advanced 3D food printers, besides having pre-loaded recipes onboard the printer, allow the users to remotely design their food on their computers, phones or some IoT device. These designs can then be loaded into the printer and saved for future use. 3D printed food can be customized in shape, colour, texture, flavor or nutrition, which makes it very useful in various fields such as space exploration and healthcare^[1].

2006: Fab@Home, a project led by a group of Cornell University students, was the first multi-material 3D printer to print food materials such as chocolate, cookie dough and cheese.

2006-2009: CandyFab, a printer by Evil Mad Scientist Laboratories, was able to print large sugar sculptures that works using hot air to selectively melt and fuse sugar grains together ^[2]

2012:  Choc Edge, the first commercially available 3D chocolate printer

2012-2015: PERFORMANCE, a project led by biozoon GmbH, focused on printing easy to chew and swallow food for seniors.

2013: The first bioprinter to print in vitro meat

2014: CocoJet, a chocolate printer by Hershey’s and 3D systems that prints various shapes, sizes, and geometries using milk, dark and white chocolate

2014: Foodini, a commercially available printer by Natural Machines, is able to print a wide range of ingredients and comes with the Foodini Creator application that can be used remotely to create your own designs.

2015: Barilla and TNO print pasta and start an annual competition for the best pasta design

2018: Novameat prints the first meat-free steak made from vegetables that mimics meat texture

There are three research 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) ^[3].

The type of food available to print with varies by printing technique^[4]. For an overview of these printing techniques, please see the section Printing Techniques below:

Extrusion Based:

• Ingredients that are inherently soft enough to extrude from a syringe/printhead, but with high enough viscosity to retain a shape^[5]. In certain cases, powdered ingredients (protein, sugar, etc) are added to increase viscosity; inherently soft materials include: purée, jelly, frosting, cheese, mashed potatoes^[6], etc.
• Certain ingredients that are not soft enough can be used if they are melted and then solidify quickly e.g. chocolate^[7]

Selective Laser Sintering & Binder Jetting:

• Powdered ingredients: sugar, chocolate powder, protein powder ^[8] , etc.

Inkjet Printing:

• Ingredients with low viscosity are used for surface filling ^[9]; such materials include: sauces (pizza, hot sauce, mustard, ketchup, etc.), colored food ink ^[10], etc.

In addition, some research has been conducted into food additives for improving the process of printing complex structures and ensuring the printed structure retains its shape in post-processing. Additives such as transglutaminase^[11] or hydrocolloids^[5] have been added to ingredients in order to help retain the printed shape while printing and after cooking .

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 ^[12] (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 deformation due to temperature fluctuations with additional baking or frying require further research and development to overcome.

In Hot-Melt extrusion, also called fused deposition modeling (FDM), 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 ^[7].

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 are able to be printed at room temperature without prior melting.

In selective laser sintering powdered food materials are heated and bonded together forming a solid structure. This process is completed by bonding the powdered material layer by layer. 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 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 sugar and sugar-rich powders ^[2]. Due to this limitation, selective laser sintering is seen as applicable to creating sweets/candies, and not nutrient rich food.

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 ^[8]. Likewise, it is also limited by the range of suitable food materials, namely sugar and sugar-rich powders, and is primarily used to create sweets/candies.

Inkjet printing is used for surface filling or image decoration ^[9]. 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 ^[10]. An issue with inkjet printing is the food materials being incompatible with the ink resulting in no image or high image distortion^[13]. Inkjet printers can be purchased for household or commercial use, and industrial printers are suitable for mass production.

In multi-printhead and multi-material printing (*Provide Link to other Wiki page*), multiple ingredients are printed at the same time or in succession^[11]. 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^[9]. In another instance, there is one printhead, and when a different ingredient is required, the printer exchanges the material being printed^[14]. 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^[4].

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 and observing what works^[11]. However, recent research has produced a 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) ^[15]. With further research and development, a visual simulation of printed foods being cooked could potentially predict what is vulnerable to deformation.

Personalized dietary requirements for an individual's nutritional requirement has been linked to the prevention of diseases ^[16]. As such, eating the correct food is paramount to leading a healthy life. 3D printing food can provide the control necessary to put a custom amount of protein, sugar, vitamins, and minerals into the foods we consume ^[17].

Another area of application in personal nutrition is the elderly. The elderly often times cannot swallow foods, and as such require a softer pallet ^[18]. However, these foods are often unappealing causing some individuals to not eat what their bodies' nutritional needs require ^[19]. 3D printed food can help by providing a soft and aesthetically pleasing food in which the elderly can consume their bodies' dietary requirements ^[20].

As the world's population continues to grow, experts believe that current food supplies will not be able to supply the population ^[21]. Thus, a sustainable food source is critical. Studies have shown that entomophagy, the consumption of insects, has the potential to sustain a growing population ^[22]. Insects such as crickets require less feed, less water, and provide around the same amount of protein that chickens, cows, and pigs do ^[22]. Crickets can be ground into a protein flour. In one study ^[23], 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.

As humans begin venturing into space longer, the nutritional requirements for maintaining crew health is critical ^[24]. Currently NASA is exploring ways of integrating 3D printing food into space in order to sustain the crew's dietary requirements ^[25]. 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 ^[26].

Livestock farming is one of the top contributors to deforestation, land degradation, water pollution and desertification. Among other reasons, this has lead to the new promising technology of bioprinting meat. One alternative to livestock farming is cultured meat, also known as lab-grown meat. Cultured meat is produced by taking a small biopsy from animals, extracting the myosatellite cells and adding growth serum to multiply 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. Novameat, a Spanish startup has been able to print a plant-based steak and mimic the texture and appearance of real meat.^[27]

Food presentation and food appearance customization for individuals is a big trend in the food industry. 3D food printing has made possible some intricate designs which cannot be accomplished with traditional food manufacturing. Brand logos, text, signatures, pictures can now be printed 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. ^[1]

Unlike traditionally prepared food, the variety of food that can be manufactured using 3D printing is limited by the physical and geometric characteristics of the materials. Food materials are generally much softer than the weakest plastic used in 3D printing, making the printed structures very fragile^[28].

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^[28].

3D printing food is still a very slow process for mass production^[29]. Simple designs take 1 to 2 minutes, fuller designs 3 to 7 minutes and more complex designs take even longer^[1].

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 than can be 3D printed, leaving out complex dishes that require a lot of different materials^[28].

When 3D printing food, the safety is very crucial. A food printer must ensure safety along the entire path taken by the food material^[28]. Due to the possibility of food getting stuck somewhere along the path, bacteria accumulation is a major concern. On the other hand, the materials that come into contact with the food are not a concern since high quality printers use stainless steal and BPA-free materials^[1].

Existing food products in the market such are 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^[30].