3D Printing of Foods. C. Anandharamakrishnan

3D Printing of Foods - C. Anandharamakrishnan


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the Massachusetts Institute of Technology (MIT) printed the melted chocolate using the direct ink writing (DIW) method using the developed 3D printer ‘Digital Chocolatier’ (Zoran and Coelho 2011). A similar approach has been used by 3D Food‐Inks Printer for the printing of 3D‐colored images on the extruded base (Golding et al. 2011). However, a post‐processing step is required for the fusion of printed layers. More recently, Rando and Ramaioli (2020) studied the effect of heat transfer on the print stability of chocolate. The study investigated the correlation between the rheological and thermal properties for achieving a well‐stable 3D structure. The stability criterion based on the developed yield stress during extrusion explained the stability or deformation of the printed materials.

Schematic illustration of hot-melt extrusion of complex 3D geometry bunny using chocolate.

      Source: From Lanaro et al. (2017), [p.30] / With permission of Elsevier. DOI‐https://doi.org/10.1016/j.jfoodeng.2017.06.029.

      The cold extrusion also known as room temperature extrusion (RTE) refers to the process of extrusion and deposition of materials without phase change. Most of the natively printable materials and pre‐processed non‐natively printable, as well as alternative ingredients, can be printed using RTE (Nachal et al. 2019). This type of extrusion is applied for the fabrication of 3D printed products that are difficult to produce by conventional food processing methods. Adoption of 3D printing would result in the production of foods with higher repeatability and smooth finish making them suitable for mass production and customization. Ready to cook (RTC) pasta products with novel 3D designs can be printed from a mixture of wheat semolina and water without the influence of temperature using RTE. Similarly, surface filling and graphical decorations of confectioneries are done using RTE (Van der Linden 2015). The semi‐solid paste‐like food materials are more appropriate for RTE; hence it is also referred to as soft material extrusion. The process involves the continuous extrusion of material from the moving print head that results in layered deposition of materials adhered to the preceding layers upon cooling without phase transition. The printing material supplies not only possess the adequate yield stress and elastic modulus but also shear‐thinning tendency to withstand the desired shape after printing (Huang 2018). Although the temperature is less significant during RTE, the temperature must be fine‐tuned that has a direct influence over the material consistency (K) and flow behaviour (n) (Hamilton et al. 2018). The printability of vegemite and marmite has been determined based on the K and n values in achieving a proper extrusion rate. Apart from the rheological properties, the particle size, crystallinity, and material composition would greatly affect the printability and quality of the 3D constructs.

      Hydrogel‐forming extrusion (HFE) is the process of the extrusion of hydrocolloid solutions/ dispersions into a polymeric/ hardening/ gel setting bath using a syringe‐based extrusion mechanism through a moving printing nozzle (Kuo et al. 2021). Here, the solution temperature is a key criterion that determines the stability of droplets. The gel droplet’s diameter ranges about 0.2–5 mm that forms a smooth distinct layer on deposition (Sun et al. 2018a). The rheological property and the gelation characteristics of the polymeric solution have significant implications on the successful printing of hydrogels. During the printing process, the polymer solution in the liquid state gets transformed into a stable gel state upon deposition. Research works on the fabrication of edible hydrogels are quite increased due to the advantage of the development of soft foods for aged people with swallowing disorders (Serizawa et al. 2014). Commercially available hydrogel printers are equipped with advanced dispensing units for the precise deposition of material. A 3D fruit printer developed by a UK firm, Dovetailed combined strawberry fruit flavour with the sodium gel for 3D printing of little spheres into a cold solution of calcium chloride bath to resemble a raspberry fruit (Molitch‐Hou 2014).