Three-dimensional (3D) printing technology was originally invented to build objects made of metals, ceramics and polymers and to perform the fabrication of complex structures and parts in a single step.
Nowadays 3D printing has been also successfully applied to food materials and is about to revolutionize food preparation, processing and manufacturing with customized abilities in product design and development. The potential applications of 3D printing include not only attributes such as decorations, complex shapes and geometries, color, flavor, elaborated texture but also tailored nutrition.
Using multiple ingredients, a food printer can formulate products based on personalized nutritional needs and can provide a potential solution as a prototyping tool to facilitate new food product development. A new level of artistic capabilities can be achieved in restaurants and the culinary sector using 3D food printing technology.
There are three categories of available materials that include natively printable food materials (cake frosting, cheese, hummus and chocolate), non-printable traditional food materials and alternative ingredients.
Printability tests for traditional food materials have been evaluated by their viscosity, consistency and solidifying properties. According to the large number of conducted tests, the most successful printable material was pasta dough. Foods like rice, meat, fruit and vegetables are not printable by nature. To enable their capability of extrusion, adding hydrocolloids in these solid materials has been utilized in many culinary fields.
Commercial and self-developed food printing platforms have been utilized to print and actually fabricate food products. A typical food printing platform consists of a three-axis stage, dispensing and sintering units and a user interface. There are several different methods and technologies for 3D printing: selective laser and hot air sintering, hot-melt extrusion or fused deposition, room temperature extrusion, binder jetting and inkjet printing. Most of these processes involve either depositing or fusing materials in a desired shape, typically melting and solidifying the material used. With a computer-controlled material feeding system, such platforms can manipulate food fabrication in real time.
The type and properties of materials and product that may be fabricated determine the suitable type of 3D printing technology. The technologies are grouped by the type of material used: powder, semi-solid, liquid or cell cultures. Cell culture-based systems have been applied for bio-printing meat.
Both laser and hot air can be utilized as a sintering source to fuse powder particles and form a solid layer. This method is only suitable for sugar and fat-based materials with a low melting point. In hot-melt extrusion, melted semi-solid food polymer is extruded from a movable head, solidifies almost immediately after extrusion, and welds to the previous layers of product. Hot temperature extrusion method has been applied to create customized 3D chocolate products. Room temperature extrusion has been used for some natively printable materials like cheese, frosting and hummus.
In binder jetting food printers, each powder layer is distributed evenly across the fabrication platform, and a liquid binder sprays to bind two consecutive powder layers. Before fabrication, a layer of water mist is sprayed to stabilize powder material and minimize disturbance caused by binder dispensing.
Inkjet food printing dispenses a stream of droplets of edible inks from a syringe-type print head in a drop-on-demand way directly onto different food surfaces. It has been used for decoration of cookies, cake, pastry fabrication or surface fill. Inkjet printing is easily automated, suitable for mass production, offers possibility for customised and personalized marking and can be integrated into existing food production lines. The drawbacks are short marking distances (<1 cm) and ink compatibility issues since theoretically every food product would require a specific ink to have good enough print quality and adhesion.
Bio-printing was originally applied to build tissues without any biomaterial-based platform. This technique relies on the precise layer-by-layer deposition of biological materials and culture of living cells.
Droplets of freshly prepared multicellular aggregates (the bio-ink particles) are deposited via an inkjet nozzle into a biocompatible support structure. The final object is transferred to special purpose bioreactor for further maintenance and maturation.
The potential uses of 3D printing food can be looked at the three levels: consumer produced foods, small-scale food production (shops, restaurants, bakeries) and industrial scale food production. Advances in 3D printing technology can significantly change and improve the way that food products are manufactured and produced. Any object can be scanned or designed with computer-aided design software and then sliced up into thin layers, which can then be printed out to form a 3D product.
Substantial efforts have been made to pre-process materials suitable for printing and improve their thermal stability for post-processing. Hence, the recipes used in printing would have to be slightly different from traditional recipes. Ingredients even with well-known material properties needed be tailored for each printing application.
Also, food safety concerns have greatly limited the applying of technologies that involve laser, electron beam and undesirable food additives in food printing. Food-safe-certified and easily cleaned printers will need to be developed.
Another limiting factor of the adoption of 3D printing as an industrial food process is the slow speed of the process. 3D printing as a whole is a slow set of technologies, often requiring hours to produce large shapes. Among many other aspects, the development of the combination of the expertise in foods with new printing technologies is crucial to print on food or print foods in industrial scale.