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Extrusion-based 3D food printing – Materials and machines

gelatin). It was found that with no gelatin added, there
was a phase separation between the solid meat and liquid
phase, resulting in nozzle occlusion and poor prints.
When gelatin was added, the overall printing process
became more consistent and smooth. Liu et al. also
found that an addition of 40g gelatin resulted in better
print quality than when only 20g was added and thus
deemed optimal by the authors. A sample print is shown
in Figure 4.
Gelatin is a proteinaceous hydrocolloid which proved Figure 5. 3D-printed food inks modified with CNF: (Left) 0.8%
useful in this case where high-protein meats were used CNF with 50% semi-skimmed milk powder. (Right) 1.5% CNF
as the food base. Upon hydration and heating up to 40 with 5% waxy maize starch. Pictures taken from an article by
[14]
°C, the gelatin amino acid chains denature and unravel Lille et al.
availing their hydrophilic R-groups to bind water. More 2.6 Crystalline nanocellulose (CNC) and nano-
importantly, when cooled down to room temperature, the fibrillated cellulose (NFC) [15]
gelatin chains renature to form random fibrillar collagen-
like helix structures which crosslink to form a thermo- This is a patent that claims to have developed a non-
reversible gel network throughout the meaty food caloric printability modifier by using indigestible
[13]
matrix . celluloses, similar to the CNF reported by Lille et al.
The intended use in this case however, has a much
wider scope. Shoseyov et al. claims to be able to use
these modified celluloses universally to print foods that
consist of a mixture of macronutrients. These include
“hamburgers, nuggets, pizza, cake, pasta, sweets, candy
etc.”. According to claim 11, protein sources may
include collagen, plant-based proteins, egg proteins and
muco-proteins. From claim 14, carbohydrate content
may come in the form of up to 30 different sugars, sugar
alcohols and glycoproteins. Fat content comes from
olive oil and also milk fat, according to claims 20 and
21. In the description, it is mentioned that the prepared
cellulose nano-material is monocrystalline (at least
Figure 4. 3D-printed cooked-meat slurry with 100g water and 40g 100nm) or fibrillar (between 100nm and 1000nm). In
gelatin powder added. Picture taken from an article by Liu et al. [12] claim 50, it also states that at least 2% of CNC and/or
NFC was used to manufacture the 3D-printable solid or
gel food product.
2.5 Cellulose nanofiber (CNF) on milk powder In the above two examples, nanocelluloses were used
and starch powder [14] as they exhibit good shear-thinning properties even at
low concentrations. More interestingly, nanocellulose
A novel material, cellulose nanofiber (CNF), was used in gel networks are capable of self-assembly in an aqueous
this study where CNF was self-prepared from dried and medium. Thus, they are a perfect fit based on the
bleached birch kraft pulp. The composition of the dried guidelines proposed in section 2.1. Also, unlike gelatin
CNF was found to be 73% cellulose, 26% hemicellulose or starch, heating and cooling cycles are not required for
and 1% lignin. A viscous hydrogel was then formed in an the formation of nanocellulose gel networks .
[16]
aqueous suspension consisting of 1.6% w/w of this dry
CNF. However, this edible hydrogel cannot be classified 2.7 Alginate and carrageenan in a variety of
as a food as it has no nutritional value. Cellulose, food material [17-22]
hemicellulose and lignin are all non-digestible by the Zhang & Zhang own a series of patents for the basic
human digestive system. Thus, milk powder and starch idea of printability modification for a variety of food
were added to this gel to form food inks with digestible materials to produce a 3D-printable rice vermicelli
proteins (from milk) and carbohydrates (from starch). noodle. The patents utilize food ingredients like
Sample prints of the milk gel and starch gel are shown in Hericium Erinaceus mushrooms, tomatoes, blueberries,
Figure 5. pumpkins, mulberries and figs to incorporate nutritional

4 International Journal of Bioprinting (2018)–Volume 4, Issue 2