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Jie Sun, Zhuo Peng, Liangkun Yan, et al

quire post-processing to improve taste and nutrition its own weight and the weight of subsequent layers,
absorption. This will make it more difficult for food without a significant deformation or change in shape.
product structures to retain their shapes [19] .
(2) Non-printable traditional food material: Food 3. 3D Food Printing Technologies
like rice, meat, fruit, and vegetables, largely consumed 3D food printing has significant advantages in
by people daily, are not printable by nature. To enable high-value, low volume food fabrication, particularly
their capability of extrusion, adding hydrocolloids in for customized items in mass food service. Some
these solid materials has been approved and utilized in printers used thermal energy from laser/hot air/heating
culinary fields. Lipton et al. [19] used simple additives element to sinter or melt powder, and others used
to modify traditional food recipes and created com- inkjet-type printing heads to accurately spray binder
plex geometries and novel formulations. Although or solvent. A summary of the applicable 3DP technol-
solid foods and semi-solid liquids have already been ogies can be found below.
manipulated to become printable by gastronomic
tricks, it is difficult to test and modify the whole list of 3.1 Current 3D Food Printing Technologies
traditional food materials. One solution is to use a
small group of ingredients to create a platform with (1) Selective Sintering technology: Sugars and sug-
extensive degrees of freedom of texture and flavor. By ar-rich powders can be selectively sintered to form
fine-tuning hydrocolloids’ concentrations, a very wide complex shapes. After a layer of fresh powder is
range of textures (i.e., mouthfeels) can be achieved spread, a sintering source (hot air in Figure 2(A) or
such as cooked spaghetti, cake icing, tomato, etc. The laser in Figure 2(B)) moves along x- and y-axes to
flavors can be altered by adjusting the amount of fla- fuse powder particles so that they can bind together
vor additives being added. Cohen et al. [21] experi- and form a solid layer. This process is repeated by
mented food texture using two hydrocolloid systems, continuously covering the fused surface with a new
and explored structural requirements for post- layer of material until the 3D object is completed [25] .
[2]
processing materials such as protein pastes and cake TNO’s Food Jetting Printer applied laser to sinter
mixtures. sugars and Nesquik powders. The sintered material
(3) Alternative ingredients: Introducing alternative formed the part whilst the un-sintered powder re-
ingredients in food products can be one of the solu- mained in place to support the structure. The Candy-
tions to deal with the global crisis of food shortage. In Fab [18] applied a selective low-velocity stream of hot
the “Insects Au Gratin” project, Susanna Soares air to sinter and melt a bed of sugar. The fabrication
et al. [24] mixed insect powders with extrudable icing powder bed is heated to just below the material melt-
and soft cheese to shape food structures and make ing point to minimize thermal distortion and facilitate
tasty pieces with 3D printing. When compared with fusion among layers. Selective sintering offers more
traditional meat products, the protein concentration in freedom to build complex food items in a short time
insect powder, an alternative source for protein intake, without post-processing. It is suitable for sugar and
is slightly higher. Food printing can greatly contribute fat-based materials with relatively low melting points.
to make unpleasant aesthetics and cultural background However, the fabrication operation is complicated as
of insects more appealing to consumers. many variables are involved.
(4) Post-processing: A majority of traditional edibles (2) Hot melt extrusion: Hot-melt extrusion, also
need post-processing, such as baking, steaming, or called fused deposition modeling (FDM), was first
frying after shapes are constructed. This involves dif- described in Crump’s work [26] . In Figure 3, melted
ferent levels of heat penetration and results in a semi-solid thermoplastic material is extruded from a
non-homogenous texture. Lipton et al. successfully movable FDM head and deposited onto a substrate.
used a modified recipe with cocoa material to print The material is heated slightly above its melting point
cookies with complex internal geometries, which so that it solidifies almost immediately after extrusion
could retain their shape after the baking process [19] . and fuses to the previous layer.
Basically, the food printing process does not require This technology is widely applied to create persona-
a high energy source to completely remove liquid lized 3D chocolate products [10,17,27] . Using FDM-based
contents from food composition. But the fabricated extrusion system, Hao et al. [17] compared the material
layer should be sufficiently rigid and strong to support properties among various food items and printed 3D

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