Scientists in Singapore have developed a method for 3D printing three-dimensional figures with milk at room temperature, which allows you to preserve its properties. They also demonstrated multicomponent printing with edible materials, for example, a milk cube containing several syrups inside. An article about the method was published in the RSC Advances journal.
There are not only methods for printing with polymers and metals, but also methods for creating freeform edible objects. Typically, one of the extrusion methods is used for this, in which the material is heated and squeezed out of a nozzle that moves over the print area, and the operation is repeated layer by layer. This is a simple method, but more often than not, the print material is heated to melt or soften, and in the case of some products, this can lead to the loss of their nutritional properties, for example, protein denaturation. Last year, Rahul Karyappa and Michinao Hashimoto of the Singapore University of Technology and Design learned how to print without heating with chocolate pastes, choosing the optimal viscosity of the material.
In their new work, Kariappa and Hashimoto, along with Cheng Pau Lee, have applied a similar cold extrusion method to print milk, which, unlike chocolate, is temperature sensitive and also usually exists in liquid or powder form. The authors decided to use dry milk without any additives mixed with water. To select the optimal composition, they printed a mesh from the material and looked at its behavior, and also measured some characteristics.
During the experiments, scientists were convinced that an aqueous solution of milk powder with a concentration of 60 to 75 percent behaves like a pseudoplastic liquid (with an increase in shear stress, its viscosity decreases), which is convenient for printing by cold extrusion. At 70 and 75 percent concentrations, the printed mesh was almost non-blurred and retained the structure similar to the target. Scientists saw the same behavior when printing a sofa model - starting with a 70% concentration, the viscosity after extrusion was sufficient so that the layers of material did not move after exiting the nozzle.
After the authors demonstrated that the composition they selected can be used for printing free-form objects, they showed that it can also be used for multicomponent printing. As an example, they printed a different model of a sofa with sides made of chocolate syrup, as well as a sealed cube with four cavities inside, which were filled with chocolate, maple and blueberry syrup and coconut paste during printing.
In 2018, Korean scientists came up with a method to print on a variety of foods with the right nutrient content and texture. The method is based on the cryogenic grinding of raw materials.